RFC 3949
File Format for Internet Fax
5. Profile J: Lossless JBIG Black-and-White Fax profile
This section defines the lossless JBIG black-and-white profile of TIFF for facsimile, designated Profile J. Implementations of this profile are required to implement Profile S as well. The previous section described the extended interchange set of TIFF fields for black-and-white fax, which provided support for the MH, MR, and MMR compression of black-and-white images. This section adds a profile with JBIG compression capability.5.1. Overview
This section describes a black-and-white profile that uses JBIG compression. The ITU-T has approved the single-progression sequential mode of JBIG [T.82] for Group 3 facsimile. JBIG coding offers improved compression for halftoned originals. JBIG compression is used in accordance with the application rules given in ITU-T Rec. T.85 [T.85]. This profile is essentially the extended black-and-white profile with JBIG compression used instead of MH, MR, or MMR.
5.2. Required TIFF Fields
This section lists the required fields and the values they must have to be ITU-compatible. Besides the fields listed in Section 2.2.1, the extended black-and-white fax profile requires the following fields.5.2.1. Baseline fields
The TIFF fields that SHALL be used in this profile are the same as those described in Section 4.2.1 for the extended black-and-white profile, with two exceptions: the following text replaces the text in Section 4.2.1 for the Compression and FillOrder fields. Compression(259) = 9. SHORT RequiredByTIFFBaseline 9 = JBIG coding. This is a TIFF extension value. Default = 1 (and is not applicable; field must be specified). Profile J uses ITU-T T.85 profile of T.82; see T82Options field. FillOrder(266) = 1, 2. SHORT RequiredByTIFFBaseline 1 = Pixels are arranged within a byte such that pixels with lower values are stored in the higher-order bits of the byte, i.e., most significant bit first (MSB). 2 = Pixels are arranged within a byte such that pixels with lower column values are stored in the lower-order bits of the bytes, i.e., least significant bit first (LSB). Profile J readers must be able to read data in both bit orders.5.2.2. Extension fields
Same fields as those in Section 2.2.1.5.2.3. New fields
T82Options(435) = 0 LONG Required when Compression = 9 Individual bits are set to indicate the applicable profile of JBIG coding; all bits set to 0 indicates ITU-T T.85 profile of T.82; Other values are for further study. Default is all bits 0, and field may be omitted if this is the value. (Field may be omitted in Profile J files.)
Note: A T.82 decoder can decode a T.85-encoded image when it handles the NEWLE marker code as described Corrigendum 1 in [T.85].5.3. Recommended TIFF Fields
See Sections 2.2.3 and 2.2.4.5.4. Profile J: Lossless JBIG Black-and-white Fax Profile Summary
Recommended fields are shown with an asterisk (*). Required fields or values are shown with a double asterisk (**). If the double asterisk is on the field name, then all the listed values are required of implementations; if the double asterisks are in the Values column, then only the values suffixed with a double asterisk are required of implementations. +---------------------------+--------------------------------+ | Baseline Fields | Values | +---------------------------+--------------------------------+ | BitsPerSample | 1** | +---------------------------+--------------------------------+ | Compression | 9**: JBIG coding | +---------------------------+--------------------------------+ | DateTime* | {ASCII}: date/time in 24-hour | | | format "YYYY:MM:DD HH:MM:SS" | +---------------------------+--------------------------------+ | FillOrder** | 1: most significant bit first | | | 2: least significant bit first | +---------------------------+--------------------------------+ | ImageDescription* | {ASCII}: A string describing | | | the contents of the image | +---------------------------+--------------------------------+ | ImageWidth | 1728**, 2048, 2432, 2592, | | | 3072, 3456, 3648, 4096, 4864 | +---------------------------+--------------------------------+ | ImageLength** | n: total number of scanlines | | | in image | +---------------------------+--------------------------------+ | NewSubFileType** | 2: Bit 1 identifies single | | | page of a multi-page document | +---------------------------+--------------------------------+ | Orientation | 1**-8, Default 1 | +---------------------------+--------------------------------+ | PhotometricInterpretation | 0: pixel value 1 means black | | ** | 1: pixel value 1 means white | +---------------------------+--------------------------------+
+---------------------------+--------------------------------+
| ResolutionUnit** | 2: inch |
| | 3: centimeter |
+---------------------------+--------------------------------+
| RowsPerStrip** | n: number of scanlines per |
| | TIFF strip |
+---------------------------+--------------------------------+
| SamplesPerPixel** | 1 |
+---------------------------+--------------------------------+
| Software* | {ASCII}: name & release |
| | number of creator software |
+---------------------------+--------------------------------+
| StripByteCounts** | <n>: number of bytes in TIFF |
| | strip |
+---------------------------+--------------------------------+
| StripOffsets** | <n>: offset from beginning of |
| | file to each TIFF strip |
+---------------------------+--------------------------------+
| XResolution | 200, 204**, 300, 400, 408 |
| | (written in pixels/inch) |
+---------------------------+--------------------------------+
| YResolution | 98**, 196**, 100, |
| | 200, 300, 391, 400 |
| | (written in pixels/inch) |
+---------------------------+--------------------------------+
| Extension Fields |
+---------------------------+--------------------------------+
| DocumentName* | {ASCII}: name of document |
| | scanned |
+---------------------------+--------------------------------+
| PageNumber** | n,m: page number followed by |
| | total page count |
+---------------------------+--------------------------------+
| New Fields |
+---------------------------+--------------------------------+
| GlobalParametersIFD* | IFD: global parameters IFD |
+---------------------------+--------------------------------+
| T82Options** | 0: T.85 profile of T.82 |
+---------------------------+--------------------------------+
| ProfileType* | n: type of data stored in file |
+---------------------------+--------------------------------+
| FaxProfile* | n: ITU-compatible fax profile |
+---------------------------+--------------------------------+
| CodingMethods* | n: compression algorithms used |
| | in file |
+---------------------------+--------------------------------+
6. Profile C: Base Color Fax profile
6.1. Overview
This section defines the lossy color profile of TIFF for facsimile, designated Profile C. Implementations of this profile are required to also implement Profile S as well. This is the base profile for color and grayscale facsimile, which means that all applications that support color fax must support this profile. The basic approach is the lossy JPEG compression [T.4, Annex E; T.81] of L*a*b* color data [T.42]. Grayscale applications use the L* lightness component; color applications use the L*, a* and b* components. This profile uses a new PhotometricInterpretation field value to describe the L*a*b* encoding specified in [T.42]. This encoding differs in two ways from the other L*a*b* encodings used in TIFF [TIFF, TTN1]: it specifies a different default range for the a* and b* components, based on a comprehensive evaluation of existing hardcopy output, and it optionally allows selectable range for the L*, a* and b* components.6.2. Required TIFF Fields
This section lists the required fields, in addition to those given in Section 2.2.1, and the values they must support to be compatible with ITU-T Rec. T.42 and Annex E in ITU-T Rec. T.4.6.2.1. Baseline Fields
ImageWidth(256). SHORT or LONG This profile supports the following fixed page widths: 864, 1024, 1216, 1728, 2048, 2432, 2592, 3072, 3456, 3648, 4096, 4864. NewSubFileType(254) = (Bit 1=1). LONG RequiredByTIFFforFAX Bit 1 is 1 if the image is a single page of a multi-page document. Default = 0 (no subfile bits on, so may not be omitted for fax). BitsPerSample(258) = 8. SHORT Count = SamplesPerPixel The base color fax profile requires 8 bits per sample.
Compression(259) = 7.
SHORT
Base color fax profile uses Baseline JPEG compression. Value 7
represents JPEG compression as specified in [TTN2].
FillOrder(266) = 1 , 2.
SHORT
RequiredByTIFFBaseline
Profile C readers must be able to read data in both bit orders,
but the vast majority of facsimile products store data LSB first,
exactly as it appears on the telephone line.
1 = Most Significant Bit first.
2 = Least Significant Bit first.
PhotometricInterpretation(262) = 10.
SHORT
Base color fax profile requires pixel values to be stored with the
CIE L*a*b* encoding defined in ITU-T Rec. T.42. This encoding is
indicated by the PhotometricInterpretation value 10, referred to
as ITULAB. With this encoding, the minimum sample value is
mapped to 0, and the maximum sample value is mapped to (2^n - 1),
i.e., the maximum value, where n is the BitsPerSample value. The
conversion from unsigned ITULAB-encoded samples values to signed
CIE L*a*b* values is determined by the Decode field; see Section
6.2.3.
NOTE: PhotometricInterpretation values 8 and 9 specify encodings for
use with 8-bit-per-sample CIE L*a*b* [TIFF] and ICC L*a*b* [TTN1]
data, but they are fixed encodings, which use different minimum and
maximum samples than the T.42 default encoding. As currently
defined, they are not able to represent fax-encoded L*a*b* data.
ResolutionUnit(296) = 2.
SHORT
The unit of measure for resolution. 2 = inch.
ITU-T standards only specify inch-based resolutions for color fax.
Default = 2 (field may be omitted if this is the value).
SamplesPerPixel(277) = 1, 3.
SHORT
1: L* component only, required in base color profile
3: L*, a*, b* components
Encoded according to PhotometricInterpretation field
XResolution(282) = 100, 200, 300, 400.
RATIONAL
YResolution(283) = 100, 200, 300, 400.
RATIONAL
The resolution of the image is expressed in pixels per resolution
unit. In pixels per inch, allowed XResolution values are 100,
200, 300, and 400. The base color fax profile requires the pixels
to be square, hence YResolution must equal XResolution. Base
resolution is 200 pixels per inch and SHALL be supported by all
implementations of this profile.
NOTE: The functional equivalence of inch-based and metric-based
resolutions is maintained, per Annex E.6.5 in [T.4]. See table in
Section 2.2.2.
NOTE: Not all combinations of XResolution, YResolution and ImageWidth
are legal. The following table gives the legal combinations for
inch-based resolutions and the corresponding paper sizes [T.30].
+--------------------------------+---------------------------+
| XResolution x YResolution | ImageWidth |
+--------------------------------+---------------------------+
| 100 x 100 | 864 | 1024 | 1216 |
+--------------------------------+---------------------------+
| 200 x 200 | 1728 | 2048 | 2432 |
+--------------------------------+---------------------------+
| 300 x 300 | 2592 | 3072 | 3648 |
+--------------------------------+---------------------------+
| 400 x 400 | 3456 | 4096 | 4864 |
+--------------------------------+---------------------------+
|Letter,A4| B4 | A3 |
| Legal | | |
+---------------------------+
| Paper Size |
+---------------------------+
6.2.2. Extension Fields
The JPEG compression standard allows for the a*b* chroma components
of an image to be subsampled relative to the L* lightness component.
The extension fields ChromaSubSampling and ChromaPositioning define
the subsampling. They are the same as YCbCrSubSampling and
YCbCrPositioning in [TIFF] but have been renamed to reflect their
applicability to other color spaces.
ChromaSubSampling(530).
SHORT
Count = 2
Specifies the subsampling factors for the chroma components of a
L*a*b* image. The two subfields of this field,
ChromaSubsampleHoriz and ChromaSubsampleVert, specify the
horizontal and vertical subsampling factors respectively.
SHORT 0: ChromaSubsampleHoriz = 1, 2.
1: equal numbers of lightness and chroma samples horizontally,
2: twice as many lightness samples as chroma samples horizontally,
SHORT 1: ChromaSubsampleVert = 1, 2.
1: equal numbers of lightness and chroma samples vertically,
2: twice as many lightness samples as chroma samples vertically,
The default value for ChromaSubSampling is (2,2), which is the
default for chroma subsampling in color fax [T.4, Annex E]. No
chroma subsampling, i.e., ChromaSubSampling = (1,1), is an option
for color fax.
ChromaPositioning(531) = 1.
SHORT
Specifies the spatial positioning of chroma components relative to
the lightness component.
1: centered, value of 1 means chrominance samples are spatially
offset and centered with respect to luminance samples. See the
current TIFF specification under YcbCr positioning for further
information.
Default = 1, which is what ITU-T T.4, Annex E specifies.
6.2.3. New Fields
Decode(433).
SRATIONAL
Count = 2 * SamplesPerPixel
Describes how to map image sample values into the range of values
appropriate for the current color space. In general, the values
are taken in pairs and specify the minimum and maximum output
value for each color component. For the base color fax profile,
Decode has a count of 6 values and maps the unsigned ITULAB-
encoded sample values (Lsample, asample, bsample) to signed L*a*b*
values, as follows:
L* = Decode[0] + Lsample x (Decode[1]-Decode[0])/(2^n -1)
a* = Decode[2] + asample x (Decode[3]-Decode[2])/(2^n -1)
b* = Decode[4] + bsample x (Decode[5]-Decode[4])/(2^n -1)
where Decode[0], Decode[2] and Decode[4] are the minimum values
for L*, a*, and b*; Decode[1], Decode[3] and Decode[5] are the
maximum values for L*, a*, and b*; and n is the BitsPerSample.
When n=8,=20 L*=Decode[0] when Lsample=0 and L*=Decode[1] when
Lsample=255.
ITU-T Rec. T.42 specifies the ITULAB encoding in terms of a range and
offset for each component, which are related to the minimum and
maximum values as follows:
minimum = - (range x offset) / 2^n - 1
maximum = minimum + range
The Decode field default values depend on the color space. For the
ITULAB color space encoding, the default values correspond to the
base range and offset, as specified in ITU-T Rec. T.42 [T.42]. The
following table gives the base range and offset values for
BitsPerSample=8, and the corresponding default minimum and maximum
default values for the Decode field, calculated using the equations
above when PhotometricInterpetation=10.
Refer to ITU-T Rec. T.42 [T.42] to calculate the range and offset,
and hence the minimum and maximum values, for other BitsPerSample
values.
+-----------------------------------------------+
| ITU-T Rec. T.42 | Decode |
+---------+-----------| base values | default values |
| BitsPer + Component +------------------+----------------------------+
| -Sample | | Range | Offset | Min | Max |
+---------+-----------+--------+---------+--------------+-------------+
| 8 | L* | 100 | 0 | 0 | 100 |
| +-----------+--------+---------+--------------+-------------+
| | a* | 170 | 128 | -21760/255 | 21590/255 |
| +-----------+--------+---------+--------------+-------------+
| | b* | 200 | 96 | -19200/255 | 31800/255 |
+---------+-----------+--------+---------+--------------+-------------+
For example, when PhotometricInterpretation=10 and BitsPerSample=8,
the default value for Decode is (0, 100, -21760/255, 21590/255,
-19200/255, 31800/255). For guidelines on the use of the Decode
field, see section 5.2.2 of [GUIDE].
6.3. Recommended TIFF Fields
See Sections 2.2.3. and 2.2.4.6.4. Profile C: Base Color Fax Profile Summary
Recommended fields are shown with an asterisk (*). Required fields or values are shown with a double asterisk (**). If the double asterisk is on the field name, then all the listed values are required of implementations; if the double asterisk is in the Values column, then only the values suffixed with a double asterisk are required of implementations. +---------------------------+--------------------------------+ | Baseline Fields | Values | +---------------------------+--------------------------------+ | BitsPerSample | 8**: 8 bits per color sample | +---------------------------+--------------------------------+ | Compression** | 7: JPEG | +---------------------------+--------------------------------+ | DateTime* | {ASCII}: date/time in 24-hour | | | format "YYYY:MM:DD HH:MM:SS" | +---------------------------+--------------------------------+ | FillOrder** | 1: most significant bit first | | | 2: least significant bit first | +---------------------------+--------------------------------+ | ImageDescription* | {ASCII}: A string describing | | | the contents of the image | +---------------------------+--------------------------------+ | ImageWidth | 864, 1024, 1216, 1728**, 2048 | | | 2432, 2592, 3072, 3456, 3648 | | | 4096, 4864 | +---------------------------+--------------------------------+ | ImageLength** | n: total number of scanlines | | | in image | +---------------------------+--------------------------------+ | NewSubFileType** | 2: Bit 1 identifies single page| | | of a multi-page document | +---------------------------+--------------------------------+ | Orientation | 1**-8, Default 1 | +---------------------------+--------------------------------+
+------------------------------------------------------------+
| PhotometricInterpretation | 10**: ITULAB |
+---------------------------+--------------------------------+
| ResolutionUnit** | 2: inch |
+---------------------------+--------------------------------+
| RowsPerStrip** | n: number of scanlines per |
| | TIFF strip |
+---------------------------+--------------------------------+
| SamplesPerPixel | 1**: L* (lightness) |
| | 3: LAB |
+---------------------------+--------------------------------+
| Software* | {ASCII}: name & release number |
| | of creator software |
+---------------------------+--------------------------------+
| StripByteCounts** | <n>: number or bytes in |
| | TIFF strip |
+---------------------------+--------------------------------+
| StripOffsets** | <n>: offset from beginning |
| | of file to each TIFF strip |
+---------------------------+--------------------------------+
| XResolution | 100, 200**, 300, 400 (written |
| | in pixels/inch) |
+---------------------------+--------------------------------+
| YResolution | 100, 200**, 300, 400 |
| | (must equal XResolution) |
+---------------------------+--------------------------------+
| Extension Fields |
+---------------------------+--------------------------------+
| DocumentName* | {ASCII}: name of scanned |
| | document |
+---------------------------+--------------------------------+
| PageNumber** | n,m: page number followed by |
| | total page count |
+---------------------------+--------------------------------+
| ChromaSubSampling | (1,1), (2, 2)** |
| | (1, 1): equal numbers of |
| | lightness and chroma samples |
| | horizontally and vertically |
| | (2, 2): twice as many lightness|
| | samples as chroma samples |
| | horizontally and vertically |
+---------------------------+--------------------------------+
| ChromaPositioning | 1**: centered |
+------------------------------------------------------------+
+---------------------------+--------------------------------+ | New Fields | +---------------------------+--------------------------------+ | Decode** | minL, maxL, mina, maxa, minb, | | | maxb: minimum and maximum | | | values for L*a*b* | +---------------------------+--------------------------------+ | GlobalParametersIFD* | IFD: IFD containing | | | global parameters | +---------------------------+--------------------------------+ | ProfileType* | n: type of data stored in | | | TIFF file | +---------------------------+--------------------------------+ | FaxProfile* | n: ITU-compatible fax profile | +---------------------------+--------------------------------+ | CodingMethods* | n: compression algorithms | | | used in file | +---------------------------+--------------------------------+ | VersionYear* | byte sequence: year of ITU std | +---------------------------+--------------------------------+7. Profile L: Lossless Color Profile
This section defines the lossless color profile of TIFF for facsimile, designated Profile L. Implementations of this profile are required to also implement Profiles S and C as well.7.1. Overview
This profile, specified in [T.43] and [T.4] Annex G, uses JBIG to code three types of color and grayscale images losslessly: one bit per color CMY, CMYK, and RGB images; a palettized (i.e., mapped) color image; and continuous tone color and grayscale images. The last two are multi-level and use the L*a*b* encoding specified in [T.42].7.1.1. Color Encoding
While under development, ITU-T Rec. T.43 was called T.Palette, as one of its major additions was palettized color images. Baseline TIFF only allows RGB color maps, but ITU-T Rec. T.43 requires L*a*b* color maps, using the encoding specified in ITU-T Rec. T.42. Palette color images are expressed with indices (bits per sample) of 12 bits or less, or optionally 13 to 16 bits, per [T.43] and Annex G in [T.4]. Profile L files use the color table in the T.43 data stream rather than the TIFF ColorMap field.
Enabling T.43 color maps in TIFF requires the extension field Indexed, as defined in [TTN1], and the PhotometricInterpretation field value 10, as defined in Section 6.2.1. The following table shows the corresponding PhotometricInterpretation, SamplesPerPixel, BitsPerSample, and Indexed field values for the different T.43 image types. +----------------------------------------------------------+ | Image Type |PhotometricIn| Samples | Bits Per | Indexed | | |-terpretation| Per Pixel| Sample | | |------------+-------------+----------+----------+---------| | RGB | 2=RGB | 3 | 1 | 0 | +----------------------------------------------------------+ | CMY | 5=CMYK | 3 | 1 | 0 | +------------+-------------+----------+----------+---------+ | CMYK | 5=CMYK | 4 | 1 | 0 | +------------+-------------+----------+----------+---------+ | Palette | 10=ITULAB | 1 | n | 1 | +------------+-------------+----------+----------+---------+ | Grayscale | 10=ITULAB | 1 |2-8, 9-12 | 0 | +------------+-------------+----------+----------+---------+ | Color | 10=ITULAB | 3 |2-8, 9-12 | 0 | +------------+-------------+----------+----------+---------+7.1.2. JBIG Compression
T.43 uses the single-progression sequential mode of JBIG, defined in ITU-T Rec. T.82. (Other compression methods are for further study.) To code multi-level images using JBIG, which is a bi-level compression method, an image is resolved into a set of bit-planes, and each bit-plane is then JBIG compressed. For continuous-tone color and grayscale images, Gray code conversion is used. The Gray code conversion is part of the data-stream encoding and is therefore invisible to TIFF.7.2. Required TIFF Fields
This section lists the required fields, in addition to those in Section 2.2.1, and the values they must have to be compatible with ITU-T Rec. T.43.
7.2.1. Baseline Fields
ImageWidth(256). SHORT or LONG Same page widths as the base color profile; see Section 6.2.1. NewSubFileType(254) = (Bit 1=1). LONG RequiredByTIFFforFAX Bit 1 is 1 if the image is a single page of a multi-page document. Default = 0 (no subfile bits on, so may not be omitted for fax). BitsPerSample(258) = 1, 2 - 8, 9 - 12. SHORT Count = SamplesPerPixel RGB, CMY, CMYK: 1 bit per sample Continuous tone (L*a*b*): 2 - 8 bits per sample, 9 - 12 bits optional. Palette color: 12 or fewer bits per sample. Note: More than 8 bits per sample is not baseline TIFF. Compression(259) = 10. SHORT 10: ITU-T Rec. T.43 representation, using ITU-T Rec. T.82 (JBIG) coding FillOrder(266) = 1 , 2. SHORT RequiredByTIFFBaseline Profile L readers must be able to read data in both bit orders, but the vast majority of facsimile products store data LSB first, exactly as it appears on the telephone line. 1 = Most Significant Bit first. 2 = Least Significant Bit first. PhotometricInterpretation(262) = 2, 5, 10. SHORT 2: RGB 5: CMYK, including CMY 10: ITULAB Image data may also be stored as palette-color images, where pixel values are represented by a single component that is an index into a color map using the ITULAB encoding. This color map is specified by the color palette table embedded in the image data stream. To use palette-color images, set the PhotometricInterpretation to 10, SamplesPerPixel to 1, Indexed to 1, and use the color map in the data stream. See Section 7.1.1 for discussion of the color encoding.
ResolutionUnit(296) = 2.
SHORT
The unit of measure for resolution. 2 = inch.
ITU-T standards only specify inch-based resolutions for color fax.
Default = 2 (field may be omitted if this is the value).
SamplesPerPixel(277) = 1, 3, 4.
SHORT
1: Palette-color image, or L*-only if Indexed = 0 and
PhotometricInterpretation is 10 (ITULAB).
3: RGB, or L*a*b*, or CMY if PhotometricInterpretation is 5
(CMYK).
4: CMYK.
XResolution(282) = 100, 200, 300, 400.
RATIONAL
YResolution(283) = 100, 200, 300, 400.
RATIONAL
The resolution of the image is expressed in pixels per resolution
unit. In pixels per inch, allowed XResolution values are 100,
200, 300, and 400. The lossless color fax profile requires the
pixels to be square, hence YResolution must equal XResolution.
Base resolution is 200 pixels per inch.
7.2.2. Extension Fields
Indexed(346) = 0, 1.
SHORT
0: not a palette-color image.
1: palette-color image.
This field is used to indicate that each sample value is an index
into an array of color values specified in the image data stream.
Because the color map is embedded in the image data stream, the
ColorMap field is not used in Profile L. Lossless color fax
profile supports palette-color images with the ITULAB encoding.
The SamplesPerPixel value must be 1.
7.2.3. New Fields
Decode(433)
SRATIONAL
Decode is used in connection with the ITULAB encoding of image
data; see Section 6.2.3.
7.3. Recommended TIFF Fields
See Sections 2.2.3. and 2.2.4.
7.4. Profile L: Lossless Color Fax Profile Summary
Recommended fields are shown with an asterisk (*). Required fields or values are shown with a double asterisk (**). If the double asterisk is on the field name, then all the listed values are required of implementations; if the double asterisks are in the Values column, then only the values suffixed with a double asterisk are required of implementations. +--------------------+--------------------------------------+ | Baseline Fields | Values | +--------------------+--------------------------------------+ | BitsPerSample | 1: Binary RGB, CMY(K) | | | 8**: 8 bits per color sample | | | 9 - 12: optional | +--------------------+--------------------------------------+ | Compression | 10**: JBIG, per T.43 | +--------------------+--------------------------------------+ | DateTime* | {ASCII}: date/time in the 24-hour | | | format "YYYY:MM:DD HH:MM:SS" | +--------------------+--------------------------------------+ | FillOrder** | 1: Most significant bit first | | | 2: Least significant bit first | +--------------------+--------------------------------------+ | ImageDescription* | {ASCII}: A string describing the | | | contents of the image | +--------------------+--------------------------------------+ | ImageWidth | 864, 1024, 1216, 1728**, 2048, 2432, | | | 2592, 3072, 3456, 3648, 4096, 4864 | +--------------------+--------------------------------------+ | ImageLength** | n: total number of scanlines in image| +--------------------+--------------------------------------+ | NewSubFileType | 2**: Bit 1 identifies single page of | | | a multi-page document | +--------------------+--------------------------------------+
+--------------------+--------------------------------------+
| Orientation | 1**-8, Default 1 |
+--------------------+--------------------------------------+
| PhotometricInter- | 2: RGB |
| pretation | 5: CMYK |
| | 10**: ITULAB |
+--------------------+--------------------------------------+
| ResolutionUnit** | 2: inch |
+--------------------+--------------------------------------+
| RowsPerStrip** | n: number of scanlines per TIFF strip|
+--------------------+--------------------------------------+
| SamplesPerPixel | 1**: L* (lightness) |
| | 3: LAB, RGB, CMY |
| | 4: CMYK |
+--------------------+--------------------------------------+
| Software* | {ASCII}: name & release number of |
| | creator software |
+--------------------+--------------------------------------+
| StripByteCounts** | <n>: number or bytes in TIFF strip |
+--------------------+--------------------------------------+
| StripOffsets** | <n>: offset from beginning of file to|
| | each TIFF strip |
+--------------------+--------------------------------------+
| XResolution | 100, 200**, 300, 400 (pixels/inch) |
+--------------------+--------------------------------------+
| YResolution | equal to XResolution (pixels must be |
| | square) |
+--------------------+--------------------------------------+
| Extension Fields |
+--------------------+--------------------------------------+
| DocumentName* | {ASCII}: name of scanned document |
+--------------------+--------------------------------------+
| PageNumber** | n,m: page number followed by total |
| | page count |
+--------------------+--------------------------------------+
| Indexed | 0: not a palette-color image |
| | 1: palette-color image |
+--------------------+--------------------------------------+
| New Fields |
+--------------------+--------------------------------------|
| Decode | minL, maxL, mina, maxa, minb, maxb: |
| | minimum and maximum values for L*a*b*|
+--------------------+--------------------------------------+
| GlobalParameters | IFD: global parameters IFD |
| IFD* | |
+-----------------------------------------------------------+
+--------------------+--------------------------------------+ | ProfileType* | n: type of data stored in TIFF file | +--------------------+--------------------------------------+ | FaxProfile* | n: ITU-compatible fax profile | +--------------------+--------------------------------------+ | CodingMethods* | n: compression algorithms used in | | | file | +--------------------+--------------------------------------+ | VersionYear* | byte sequence: year of ITU fax std | +--------------------+--------------------------------------+8. Profile M: Mixed Raster Content Profile
This section defines the Mixed Raster Content profile of TIFF for facsimile, designated Profile M. Implementations of this profile are required to implement Profiles S and C and may optionally implement Profiles F, J and L.8.1. Overview
Unlike previous fax profiles, which use a single coding method and resolution for an entire fax page, Mixed Raster Content [T.44] enables different coding methods and resolutions within a single page. For example, consider a page that contains black-and-white text, which is best coded with MMR or JBIG; a color bar chart, best coded with JBIG; and a scanned color image, best coded with JPEG. Similarly, although spatial resolution of 400 pixels per inch may be best for the black-and-white text, 200 pixels per inch is usually sufficient for a color image. Rather than applying one coding method and resolution to all elements, MRC allows multiple coders and resolutions within a page. By itself, MRC does not define any new coding methods or resolutions. Instead it defines a 3-layer image model for structuring and combining the scanned image data. The MRC 3-layer model has been applied here with the TIFF format to yield a data structure that differs from [T.44], though it applies the same coding methods, uses the same compressed image data streams, and is consistent with the TIFF principle of a single IFD per image.8.1.1. MRC 3-layer model
The 3 layers of the MRC model are Foreground and Background, which are both multi-level, and Mask, which is bi-level. Each layer may appear only once on a page and is coded independently of the other two layers. The final image is obtained by using the Mask layer to determine whether output pixels come from the Foreground layer or the Background layer. When the Mask layer pixel value is 1, the
corresponding pixel from the Foreground layer is selected; when it is 0, the corresponding pixel from the Background layer is selected. Details are given in the Introduction of [T.44]. In our earlier example, the shape of the black-and-white text and the mask for the color chart could be in the Mask layer, the color of the chart and text in the Foreground layer, and the color image in the Background layer. If a Mask layer pixel has a value of 1, the final image pixel will be, depending on the pixel location, from either the color chart or text color in the Foreground layer. If a Mask layer pixel has a value of 0, the final image pixel will be from the color image in the Background layer. Each layer is an image and, when present, is represented by at least one IFD in a TIFF file. This is consistent with TIFF, which provides fields to define the attributes, such as resolution, image size, bits per sample, etc., of a single image or layer. The distribution of content among layers is determined by the writer, as is the choice of coding method, color encoding, and spatial resolution for a layer. Not all pages, and not all parts of a page, require 3 layers. If a page has of only one layer, then that layer is the primary image whether it is a Background, Mask, or Foreground layer. If there is more than one layer, then the Mask must be one of the layers, in which case it is the primary image. In all cases, the primary image must be page size. MRC [T.44] allows a page to be transmitted as a series of stripes, each consisting of 1, 2 or 3 layers. The number of scanlines in each stripe can vary over the page. Although [T.44] does not allow overlap between images of a single layer, the MRC profile permits overlapping IFDs when one of the IFDs is used only to define a default image color. According to [T.4] Annex H, stripes having more than 1 layer SHOULD NOT be more than 256 lines in length unless the capability to receive longer stripes has been negotiated. Furthermore, color fax also requires the spatial resolutions of Background and Foreground images to be legal fax values that are also integer factors of the Mask image resolution. For example, if the Mask-Layer resolution is 400 pixels per inch, then allowable resolutions for the Foreground and Background layers are 100, 200, or 400 pixels per inch; if the Mask is at 300 pixels per inch, then allowable values are 100 and 300. The Foreground and Background layer resolutions can be set independently of each other.
8.1.2. A TIFF Representation for the MRC 3-layer model
In the TIFF representation of the 3-layer MRC model, each page is represented by a single IFD, called the Primary IFD. The nextIFD offset associated with a Primary IFD will point to the Primary IFD of the next page. If the page consists of a single layer, then the Primary IFD represents that layer. If more than one layer is present, the Primary IFD represents the Mask layer and the other layers are represented by a set of child IFDs that are referenced through the SubIFD extension field [TTN1] of the Primary IFD. To distinguish MRC-specific SubIFDs from other SubIFDs, the NewSubFileType field MUST have Bit 4 ON, indicating an MRC-related IFD. A new ImageLayer field is also introduced that consists of two values that identify the layer (Foreground, Background, or Mask) and the order within the layer (first, second, ... image of the layer); see Section 8.2.3. In Profile M, the Primary IFD represents a complete layer and corresponds to the primary image described in Section 8.1.1. There must be no other MRC-related IFDs or SubIFDs that contain image data corresponding to the layer represented by the Primary IFD. MRC [T.44] allows a page to be transmitted as a series of stripes. A strip within an IFD in a Profile M file represents a stripe in a [T.44] data stream. The [T.44] stripes of the Primary image are represented by a single, multiple-strip IFD; the [T.44] stripes of other layers are represented as multiple, single-strip IFDs. The layer represented by the Primary IFD may consist of strips of image data, but all the strips must be part of the single Primary IFD. For example, if the page consisted of only the Background layer, then all strips associated with the Background layer must be treated as a single image. Because MRC allows stripes with variable numbers of scanlines, a reader MUST support StripRowCounts field, as a writer may use it in place of the RowsPerStrip field to support a variable number of scanlines in each strip of the Primary IFD. In accordance with [TTN2], each strip shall be independently encoded, but coding parameters may not change between strips. Layers other than the layer represented by the Primary IFD store each strip as a separate IFD, allowing the coding parameters to change from strip to strip as described by the MRC standard [T.44]. In all cases, if the Mask layer exists, it shall be represented by a single IFD and a single set of coding parameters. The use of SubIFDs to store child IFDs is described in [TTN1]. When the Mask is the primary image, the Background and Foreground layer images are represented with child IFDs referenced by the SubIFDs
field in the Primary IFD. There are multiple ways to organize the
images of the Background and Foreground layer images: (1) the SubIFD
field of the Primary IFD is an array of pointers to all child image
IFDs, one entry per child image; (2) the SubIFD field is a single
pointer to a linked list of all child image IFDs; (3) the SubIFD
field is an array of two pointers, where the first pointer is to a
linked list of all Background layer image IFDs, and the second
pointer is to a linked list of all Foreground layer image IFDs. A
Profile M writer SHOULD structure the Background and Foreground layer
images by using (3), as shown in the example below. Furthermore, the
child IFDs representing the images of the Background and Foreground
layers SHOULD be ordered in the file in the same order as they occur
on the page. However, a Profile M reader must scan all available
child IFDs to locate and identify IFDs associated with MRC layers.
(nextIFD)
PRIMARY IFD PAGE 0 -----------------------> PRIMARY IFD PAGE 1--> ...
ImageLayer = [2,1]
NewSubFileType = 18
SubIFD[0] ---------------------- SubIFD[1]
| |
V V
Child IFD Child IFD
ImageLayer = [1,1] ImageLayer [3,1]
NewSubFileType = 16 NewSubFileType 16
| |
|(nextIFD) |(nextIFD)
V V
Child IFD Child IFD
ImageLayer = [1,2] ImageLayer [3,2]
NewSubFileType = 16 NewSubFileType 16
| |
|(nextIFD) |(nextIFD)
V V
Child IFD Child IFD
ImageLayer = [1,3] ImageLayer [3,3]
NewSubFileType = 16 NewSubFileType 16
| |
|(nextIFD) |(nextIFD)
V V
0 0
The XPosition and YPosition TIFF fields specify the offset to the
upper left corner of the IFD in resolution units, which are inches in
Profile M; see Section 8.2.2. The Primary IFD must not use XPosition
or YPosition fields.
MRC [T.44] allows the specification of a default image color that is to be applied in the event no image data is transmitted for a given stripe and layer. The new field ImageBaseColor is used to store default image color specifications in Profile M, see 8.2.3. By setting the StripByteCounts array to zero values, an IFD defining a default color but containing no encoded image data can be specified. ImageBaseColor can also be used in IFDs that contain encoded image data. In that case, the fields of the IFD must accurately reflect the encoding of the image data. If the StripByteCount entry for a given strip is 0, then the ImageBaseColor is used for that strip. If the encoded image data is ITU L*a*b, the ImageBaseColor is interpreted with the encoding parameters of the image data. If the image data is not ITU L*a*b*, the ImageBaseColor is interpreted as 8-bit ITU L*a*b*; see Section 8.2.3.8.2. Required TIFF Fields
This section describes the TIFF fields required, in addition to those in Section 2.2.1, to represent MRC fax images. Since MRC stores fax data as a collection of images corresponding to layers or parts of layers, the coding methods, color encodings, and spatial resolutions used by previous profiles apply to Profile M. Therefore, the descriptions here will typically reference the appropriate earlier sections. Fields and values specific to Profile M are pointed out.8.2.1. Baseline Fields
ImageWidth(256). SHORT or LONG Same page widths as Profile C, the base color profile; see Section 6.2.1. In Profile M, the width of a Foreground or Background image in the coded data stream may be less than the page width, unless the Background or Foreground is the primary image, in which case the width of the coded data stream is the page width. The ImageWidth field will always store the actual width of the coded data. NewSubFileType(254) = 16, 18. LONG For Profile M, the NewSubFileType field has two bits that are required. Bit 1 indicates a single page of a multi-page document and must be set for the Primary IFD; Bit 4 indicates the MRC imaging model as described in ITU-T Recommendation T.44 [T.44] and must be set for Primary IFDs and all MRC-specific child IFDs.
BitsPerSample(258) = 1, 2-8, 9-12
SHORT
SamplesPerPixel(277) = 1, 3, 4.
SHORT
Compression(259) = 1, 3, 4, 7, 9, 10.
SHORT
For Mask layer, see Sections 4.2.1 and 5.2.1. For Foreground and
Background layers, see Sections 6.2.1 and 7.2.1 Compression=1 is
not used by previous profiles. An IFD used only to specify the
default image color for a layer and strip will not have any
encoded image data associated with it, i.e., the StripByteCounts
field will contain a 0. Since no image data exists in the IFD,
the Compression field shall be set to 1, indicating no
compression. A Compression field value of 1 is not allowed for
any other IFDs.
FillOrder(266) = 1 , 2.
SHORT
RequiredByTIFFBaseline
Profile M readers must be able to read data in both bit orders,
but the vast majority of facsimile products store data LSB first,
exactly as it appears on the telephone line
1 = Most Significant Bit first.
2 = Least Significant Bit first.
PhotometricInterpretation(262) = 0, 2, 10.
SHORT
For Mask layer, 0. For Foreground and Background layers, see
Sections 6.2.1 and 7.2.1.
ResolutionUnit(296) = 2.
SHORT
The unit of measure for resolution. 2 = inch.
ITU-T standards only specify inch-based resolutions for color fax
Default = 2 (field may be omitted if this is the value).
StripByteCounts(279)
SHORT or LONG
In Profile M, it is permissible for the StripByteCounts value for
a given strip to have a zero entry. This means there is no
encoded image data corresponding to that strip. Instead, the
current default image color should be used for the strip. The
standard default image colors are black for the Foreground layer
and White for the Background layer. The ImageBaseColor field can
be used to specify other default colors; see Section 8.2.3.
XResolution(282) = 100, 200, 300, 400.
RATIONAL
YResolution(283) = 100, 200, 300, 400.
RATIONAL
The resolution of the image is expressed in pixels per resolution
unit. In pixels per inch, allowed XResolution values for all
layers are 100, 200, 300, and 400. Color fax requires the pixels
to be square, hence YResolution must equal XResolution for all
layers. The resolution of Background and Foreground layers must
each be an integer factor of the Primary image, which is the Mask
layer, when it is present; see Section 8.4.
8.2.2. Extension Fields
ChromaSubSampling(530).
SHORT
ChromaPositioning(531).
SHORT
For Foreground and Background layers, see Section 6.2.2.
Indexed(346) = 0, 1.
SHORT
For Foreground and Background layers: 1 indicates a palette-color
image; see Section 7.2.2.
T4Options(292) = 0, 1, 4, 5.
SHORT
T6Options(293) = 0.
SHORT
For Mask layer, see Section 4.2.2.
SubIFDs(330).
IFD
Count = number of child IFDs. Each value is an offset from the
beginning of the TIFF file to a child IFD [TTN1].
XPosition(286).
RATIONAL
YPosition(287).
RATIONAL
Specifies the horizontal and vertical offsets of the top left of
the IFD from the top left of the Primary IFD in resolution units.
For example, if the Primary IFD is at 400 pixels per inch, and a
foreground layer IFD is at 200 pixels per inch and located at
pixel coordinate (345, 678) with respect to the Primary IFD, the
XPosition value is 345/400 and the YPosition value is 678/400 in
inches.
The Primary IFD does not use the XPosition or YPosition fields.
The XPosition and YPosition values must be specified for MRC child
IFDs; there is no default value.
8.2.3. New Fields
Decode(433).
SRATIONAL
For Foreground and Background layers, see Section 6.2.3.
T82Options(435)
LONG
For Mask layer, see Section 5.2.3.
ImageBaseColor(434).
SHORT
Count = SamplesPerPixel
In areas of an image layer where no image data is available (i.e.,
where no strips are defined, or where the StripByteCounts entry for
a given strip is 0), the color specified by ImageBaseColor will be
used.
If the ImageBaseColor field is used in an IFD that contains image
data encoded in ITU L*a*b*, then the ImageBaseColor will be
interpreted with the color-encoding parameters of the image data
(i.e., color gamut, illuminant, bit/sample, and decode). If the
ImageBaseColor field is used in an IFD that contains image data that
is not encoded in ITU L*a*b, then the ImageBaseColor SHALL be
interpreted as 8 bits/sample, 3 samples/pixel ITU L*a*b*. If the
ImageBaseColor field is used in an IFD that contains no encoded
image data, then the ImageBaseColor SHALL be interpreted as 8
bits/sample, 3 samples/pixel ITU L*a*b*. If the fax data stream
requires a different encoding, then transferring the default color
value between a TIFF file and fax data stream requires a color
conversion.
A [T.44] stripe may contain a Foreground or Background image less
than full stripe size, with the rest of the stripe assuming a
default image color. In this case, the default image color is imaged
first, followed by the image data. In Profile M, this is represented
as a child IFD containing no encoded image data but specifying the
default image color in the ImageBaseColor field. A second child IFD
contains the image data. To ensure the default image color is imaged
first, the order value in the ImageLayer field of the IFD defining
the ImageBaseColor field MUST have a lower value than the order
value in the ImageLayer field of the IFD defining the image data.
To define a child IFD specifying a ImageBaseColor but containing no
encoded image data, create an IFD with the following settings.
ImageLayer[0]: specified layer
ImageLayer[1]: less than any other IFDs corresponding
to the same layer and strip.
RowsPerStrip: strip height
ImageLength: strip height
ImageWidth: full image width
BitsPerSample: 8
PhotometricInterpretation: 10 (ITULAB)
SamplesPerPixel: 3
Compression: 1 (none)
X/YResolution: that of the Primary IFD
XPosition: 0
YPosition: the offset from the top of the page to
the beginning of the strip in the
resolution units of inches
StripByteCounts: single 0 value
StripOffsets: single 0 entry
NewSubFileType: bit 4 O (MRC)
ImageBaseColor: desired color in 8 bit ITULAB
For the Foreground layer image, the default value for the
ImageBaseColor field is black. For other cases, including the
Background layer image, the default value is white.
StripRowCounts(559).
LONG
Count = number of strips.
The number of scanlines stored in a strip. Profile M allows each
fax strip to store a different number of scanlines. For strips
with more than one layer, the maximum strip size is either 256
scanlines or full page size. The 256 maximum SHOULD be used
unless the capability to receive longer strips has been
negotiated. This field replaces RowsPerStrip for IFDs with
variable-size strips. Only one of the two fields, StripRowCounts
and RowsPerStrip, may be used in an IFD.
ImageLayer (34732).
LONG
Count = 2.
Image layers are defined such that layer 1 is the Background
layer, layer 3 is the Foreground layer, and layer 2 is the Mask
layer, which selects pixels from the Background and Foreground
layers. The ImageLayer tag contains two values, which describe
the layer to which the image belongs and the order in which it is
imaged.
ImageLayer[0] = 1, 2, 3.
1: Image is a Background image, i.e., the image that will appear
whenever the Mask contains a value of 0. Background images
typically contain low-resolution, continuous-tone imagery.
2: Image is the Mask layer. In MRC, if the Mask layer is present,
it must be the Primary IFD and be full page in extent.
3: Image is a Foreground image, i.e., the image that will appear
whenever the Mask contains a value of 1. The Foreground image
generally defines the color of text or lines but may also
contain high-resolution imagery.
ImageLayer[1]:
1: first image to be imaged in this layer
2: second image to be imaged in this layer
3: ...
In Profile M, more than one image can exist in a single layer.
ImageLayer[1] specifies the order in which images within a single
layer are to be imaged. This insures that overlapping images
within a single layer are imaged correctly.
If an IFD contains no encoded image data and is used only to
specify the ImageBaseColor field, the value of ImageLayer[1] must
be less than that of any other IFD corresponding to the same layer
and strip to ensure the image data is interpreted as on top of the
default color.
In Profile M, it is possible to have only a single layer. For
example, if a page contains only a single continuous-tone
photograph, then only the Background layer would occur. In this
case, the Background layer will be stored as the Primary IFD.
ImageLayer[0] will be 1, indicating Background; ImageLayer[1] will
be 1, as there can be no other IFDs associated with that layer.
No Mask layer will exist.
8.3. Recommended TIFF Fields
See Sections 2.2.3. and 2.2.4.
8.4. Rules and Requirements for Images
Profile M defines a fundamental set of rules for images in the 3
layer representation.
1. If more than one layer exists, then the binary Mask layer SHALL be
present and be the primary image. The Mask layer SHALL support
the binary data representations defined in Section 3 and MAY
support those defined in Sections 4 and 5, with the exception that
PhotometricInterpretation MUST be 0. If only one layer exists,
then the image corresponding to that layer is the primary image.
2. The Primary IFD defines and extends to the entire page boundary;
all attached model images cannot extend beyond the Primary image.
Resolution differences may cause some pixels to "hang over" the
page boundary, but no new pixels should exist completely beyond
the page extent.
3. The Background and Foreground images SHALL support the color
representations defined in Section 6 and MAY support those defined
in Section 7. These images MAY optionally cover only a portion of
the strip or page.
4. Each Primary IFD and each MRC-specific SubIFD must have an
ImageLayer field to specify which layer the IFD belongs to, and
the imaging order of that IFD within the layer.
5. Each Primary IFD must have a NewSubFileType field value set to 18,
indicating a single page of a multi-page document (bit 1) and MRC
(bit 4).
6. Each MRC-specific child IFD must have a NewSubFileType field value
set to 16, indicating MRC (bit 4).
7. In MRC fax, each layer is transmitted as a sequence of strips. If
the page consists of a single layer, then all strips shall be
stored in the single Primary IFD. In this case, coding parameters
cannot change between strips. If the page consists of more than
one layer, then all strips of the Mask layer shall be stored in
the single Primary IFD. All strips of the Foreground/Background
layers SHALL be stored in separate IFDs, referenced by the Primary
IFD's SubIFD field, containing an ImageLayer field with
ImageLayer[0] identifying either Background (layer 1) or
Foreground (layer 3), and Imagelayer[1] identifying order in which
images within a single layer are to be imaged. The TIFF XPosition
and YPosition fields are used to indicate the placement of these
images with respect to the primary image.
8. When the Mask image is present, the resolution of Background and
Foreground images must each be an integer factor of the Mask
image. For example, if the Mask image is 400 pixels/inch, then
the Background or Foreground image may be at 400 pixels/inch
(400/1), 200 pixels/inch (400/2), or 100 pixels/inch (400/4).
8.5. Profile M: MRC Fax Profile Summary
Recommended fields are shown with an asterisk (*). Required fields or values are shown with a double asterisk (**). If the double asterisk is on the field name, then all the listed values are required of implementations; if the double asterisk is in the Values column, then only the values suffixed with a double asterisk are required of implementations. +------------------+-----------------------------------------+ | Baseline Fields | Values | +------------------+-----------------------------------------+ | BitsPerSample | 1**: binary mask, RGB, CMY(K) | | | 2 - 8**: bits per color sample | | | 9 - 12: optional 12 bits/sample | +------------------+-----------------------------------------+ | Compression | 1: None (ImageBaseColor IFD only) | | | 3**: Modified Huffman and Modified READ | | | 4: Modified Modified READ | | | 7**: JPEG | | | 9: JBIG, per T.85 | | | 10: JBIG, per T.43 | +------------------+-----------------------------------------+ | DateTime* | {ASCII): date/time in the 24-hour format| | | "YYYY:MM:DD HH:MM:SS" | +------------------+-----------------------------------------+ | FillOrder** | 1: Most significant bit first | | | 2: Least significant bit first | +------------------+-----------------------------------------+ | ImageDescription*| {ASCII}: A string describing the | | | contents of the image. | +------------------+-----------------------------------------+ | ImageWidth | 864, 1024, 1216, 1728**, 2048, 2432, | | | 2592, 3072, 3456, 3648, 4096, 4864 | | | Note: legal widths for the Primary IFD. | +------------------+-----------------------------------------+ | ImageLength** | n: total number of scanlines in image | +------------------+-----------------------------------------+ | NewSubFileType** | 16, 18: | | | Bit 1 indicates single page of a multi- | | | page document on Primary IFD | | | Bit 4 indicates MRC model | +------------------+-----------------------------------------+
+------------------+-----------------------------------------+
| Orientation | 1**-8, Default 1 |
+------------------+-----------------------------------------+
| PhotometricInter | 0**: WhiteIsZero (Mask Layer) |
| pretation | 2: RGB |
| | 10**: ITULAB |
+------------------+-----------------------------------------+
| ResolutionUnit** | 2: inch |
+------------------+-----------------------------------------+
| RowsPerStrip | n: number or scanlines per strip |
+------------------+-----------------------------------------+
| SamplesPerPixel | 1**: L* (lightness) |
| | 3: RGB, LAB, CMY |
| | 4: CMYK |
+------------------+-----------------------------------------+
| Software* | {ASCII}: name & release number of |
| | creator software |
+------------------+-----------------------------------------+
| StripByteCounts**| <n>: number or bytes in each strip |
+------------------+-----------------------------------------+
| StripOffsets** | <n>: offset from beginning of file to |
| | each TIFF strip |
+------------------+-----------------------------------------+
| XResolution | 100, 200**, 300, 400 (written in |
| | pixels/inch) |
+------------------+-----------------------------------------+
| YResolution | equal to XResolution (pixels must be |
| | square) |
+------------------+-----------------------------------------+
| Extension Fields |
+------------------+-----------------------------------------+
| T4Options | 0**: required if Compression is Modified|
| | Huffman, EOLs not byte aligned |
| | 1: required if Compression 2D Modified |
| | READ, EOLs are not byte aligned |
| | 4**: required if Compression Modified |
| | Huffman, EOLs byte aligned |
| | 5: required if Compression 2D Modified |
| | READ, EOLs are byte aligned |
+------------------+-----------------------------------------+
| T6Options | 0: required if Compression is 2D |
| | Modified Modified READ |
+------------------+-----------------------------------------+
| DocumentName* | {ASCII}: name of scanned document |
+------------------+-----------------------------------------+
| PageNumber** | n,m: page number followed by total page |
| | count |
+------------------+-----------------------------------------+
+------------------+-----------------------------------------+ | ChromaSubSampling| (1,1), (2, 2)** | | | (1, 1): equal numbers of lightness and | | | chroma samples horizontally & vertically| | | (2, 2): twice as many lightness samples | | | as chroma horizontally and vertically | +------------------+-----------------------------------------+ | ChromaPositioning| 1: centered | +------------------+-----------------------------------------+ | Indexed | 0: not a palette-color image | | | 1: palette-color image | +------------------+-----------------------------------------+ | SubIFDs | <IFD>: byte offset to FG/BG IFDs | +------------------+-----------------------------------------+ | XPosition | horizontal offset in primary IFD | | | resolution units | +------------------+-----------------------------------------+ | YPosition | vertical offset in primary IFD | | | resolution units | +------------------+-----------------------------------------+ | New Fields | +------------------+-----------------------------------------+ | Decode | minL, maxL, mina, maxa, minb, maxb: | | | minimum and maximum values for L*a*b* | +------------------+-----------------------------------------+ | ImageBaseColor | a,b,c: background color in ITULAB | +------------------+-----------------------------------------+ | StripRowCounts | <n>: number of scanlines in each strip | +------------------+-----------------------------------------+ | ImageLayer | n, m: layer number, imaging sequence | | | (e.g., strip number) | +------------------+-----------------------------------------+ | T82Options | 0: T.85 profile of T.82 coding | +------------------+-----------------------------------------+ | GlobalParameters | IFD: global parameters IFD | | IFD* | | +------------------+-----------------------------------------+ | ProfileType* | n: type of data stored in TIFF file | +------------------+-----------------------------------------+ | FaxProfile* | n: ITU-compatible fax profile | +------------------+-----------------------------------------+ | CodingMethods* | n: compression algorithms used in file | +------------------+-----------------------------------------+ | ModeNumber* | n: version of T.44 standard | +------------------+-----------------------------------------+ | VersionYear* | byte sequence: year of ITU fax standard | +------------------+-----------------------------------------+