ISO/IEC 23008-12:2025/Amd 1:2025

International
Standard
ISO/IEC 23008-12
Third edition
Information technology — High
2025-07
efficiency coding and media
delivery in heterogeneous
AMENDMENT 1
environments —
2025-10
Part 12:
Image File Format
AMENDMENT 1: Support for tone map
derivation and other technologies
Technologies de l'information — Codage à haute efficacité et
livraison des medias dans des environnements hétérogènes —
Partie 12: Format de fichier d'image
AMENDEMENT 1: Support pour la dérivation de la carte des
tonalités et autres technologies
Reference number
ISO/IEC 23008-12:2025/Amd. 1:2025(en) © ISO/IEC 2025

ISO/IEC 23008-12:2025/Amd. 1:2025(en)
© ISO/IEC 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
© ISO/IEC 2025 – All rights reserved
ii
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
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ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations,
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The procedures used to develop this document and those intended for its further maintenance are described
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of document should be noted. This document was drafted in accordance with the editorial rules of the ISO/
IEC Directives, Part 2 (see www.iso.org/directives or www.iec.ch/members_experts/refdocs).
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In the IEC, see www.iec.ch/understanding-standards.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
A list of all parts in the ISO/IEC 23008 series can be found on the ISO and IEC websites.
Any feedback or questions on this document should be directed to the user’s national standards
body. A complete listing of these bodies can be found at www.iso.org/members.html and
www.iec.ch/national-committees.

© ISO/IEC 2025 – All rights reserved
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ISO/IEC 23008-12:2025/Amd. 1:2025(en)
Information technology — High efficiency coding and media
delivery in heterogeneous environments —
Part 12:
Image File Format
AMENDMENT 1: Support for tone map derivation and other
technologies
Clause 2
Add the following normative references to Clause 2:
ISO/CIE 11664-3, Colorimetry — Part 3: CIE tristimulus values
ISO/CIE 11664-4, Colorimetry — Part 4: CIE 1976 L*a*b* colour space
ISO 21496-1, Digital photography — Gain map metadata for image conversion — Part 1: Dynamic range
conversion
Subclause 3.1
Add the following terms:
3.1.53
merge region item
region item (3.1.45) associated with an image item (3.1.19) that represents an approximate, merge or
summary of one or more region items associated with one or more other image items
3.1.54
tone-map derived image item
derived image item (3.1.9) of type 'tmap' where the operation (3.1.34) is to apply the output image (3.1.35)
of a gain map image item (3.1.56) to the output image of a base image item (3.1.55) according to ISO 21496-1
Note 1 to entry: ISO 21496-1 gain maps can for example be used to create a fully defined backwards compatible
transformation from SDR to HDR output and vice-versa.
3.1.55
base image item
image item (3.1.19) that is the first input to a tone-mapderived image item (3.1.54)
3.1.56
gain map image item
image item (3.1.19) that is the second input to a tone-map derived image item (3.1.54)
3.1.57
backward playback
playback of timed content in reverse chronological order

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
Subclause 3.2
Add the following abbreviated terms:
SDR standard dynamic range
Subclause 6.4
Subclause 6.4.4
nd
Replace the 2 sentence with:
The thumbnail image and master image(s) are linked using a reference type 'thmb' from the thumbnail
image to the master image.
Subclause 6.4.5
rd
Replace the 3 sentence with:
The auxiliary image and master image(s) are linked using an item reference of 'auxl' from the auxiliary
image to the master image.
Subclause 6.4.9
Add the following new subclauses after subclause 6.4.9:
6.4.10  Overview images
An overview image is described by a grid derived image item or a tiled pre-derived coded image item
or a tiled image item whose reconstructed image is formed from generating a lower resolution, ‘binned’
version of the reconstructed image of a base image item. The base image item is also tiled. The tiling may
be implemented using a feature of a specific codec, or by using a grid derived image item, or by using a tiled
image item. When a grid derived image item is used, the input items to the grid define the tiles. Derived
image items shall not be used as inputs to the image grid, due to the need for in place byte range accessing of
content. Individual tiles shall be written contiguously in memory, thereby allowing access with a single read
or write action.
A pre-derived coded image item representing an overview image or an image item representing the base
image that are tiled using a feature of a specific codec shall be stored in such a way that each extent identifies
that data range corresponding to a tile and shall be associated with a ConstrainedExtentsGridProperty
indicating the constraint on the extents and describing the tiling grid.
In cases where the binned resolution results in a fractional, or incomplete tile at the end of a row (column),
the last tile in a row (column) of tiles shall be padded with the value zero at the end of the row (column)
to complete the last tile in the row (column). If necessary, the clean aperture transformative property
('clap') may be applied to crop padded rows and/or columns. The number of tiles in a row (column) of tiles
is determined by dividing the width (height) of the overview image by the tile size in X (tile size in Y) and
rounding up.
The image format of the overview images is the same as the base image. i.e. number of bands, bit depth,
colour format, etc.
© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
Overview images can be stacked together with the base image as a series of progressively binned images in
an image pyramid entity group as defined in 6.8.11.
NOTE 1 In this version of the document, the exact derivation process (approaches such as the sum, average, median,
minimum, or maximum value of a binned region) used to produce an overview from the base image is left to the
implementer.
NOTE 2 When removing (or modifying) an item that is marked as the base image of an overview image, the content
of associated image overview items might need to be removed (or rewritten).

Clause 6.5
Clauses 6.5.18.1, 6.5.19.1, 6.5.20.1, 6.5.27.1, 6.5.35.1
Replace the word "item_ID" with the phrase "identifier value"
Clauses 6.5.18.1, 6.5.19.1, 6.5.20.1, 6.5.27.1, 6.5.35.1
Append the following text as a new paragraph:
If this property is associated with an entity group, the FileTypeBox or the ExtendedTypeBox associated with
the FileTypeBox shall indicate that the requirements of the 'unif' brand apply in the file.

Subclause 6.5.39.1
Append the following sentence and NOTE to the first paragraph and renumber existing NOTEs accordingly.
The CameraExtrinsicMatrixProperty describes the camera extrinsics of the item output image.
NOTE 1 As specified in clause 6.5.1, all descriptive properties that come after transform properties are ignored.
This means that CameraExtrinsicMatrixProperty needs to precede all transform properties even though it
describes the output image.
Subclause 6.5.40.1
Append the following sentence and NOTE to the first paragraph. Renumber existing NOTEs accordingly.
The CameraIntrinsicMatrixProperty describes the camera intrinsics of the item output image.
NOTE 1 As specified in clause 6.5.1, all descriptive properties that come after transform properties are ignored.
This means that CameraIntrinsicMatrixProperty needs to precede all transform properties even though it
describes the output image.
Replace the following:
The values of the above intrinsic matrix can be calculated as follows:
f = focal_length_x × image_width /denominator
x
f = focal_length_y × image_height /denominator
y
c = principal_point_x × image_width /denominator
x
© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
c = principal_point_y × image_height /denominator
y
s = skew_factor /skewDenominator
where image_width and image_height come from the ImageSpatialExtentsProperty associated with the
image item.
with
The values of the above intrinsic matrix can be calculated as follows:
f = focal_length_x × imageWidth / denominator
x
f = focal_length_y × imageHeight / denominator
y
c = principal_point_x × imageWidth / denominator
x
c = principal_point_y × imageHeight / denominator
y
s = skew_factor / skewDenominator
where imageWidth and imageHeight are the output dimensions of the image item after applying all
transformative properties, if any. If no transformative properties are associated with the item this translates
respectively to the dimensions image_width and image_height in the ImageSpatialExtentsProperty.

Subclause 6.5.40
Add the following new subclauses after subclause 6.5.40. Renumber tables as needed:

6.5.41  Constrained extents grid
6.5.41.1  Definition
'cexg'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one

The ConstrainedExtentsGridProperty descriptive item property indicates that each extent of the associated
image item in the itemLocationBox is constrained to enclose data units of the item that are extractable as a
contiguous byte range and are independently decodable and renderable as image tiles.
The configuration data needed to decode each extent independently may be present in the ExtentDecoderC
onfigurationRecord within the ConstrainedExtentsGridProperty. If the configuration data is not present
in the ConstrainedExtentsGridProperty, all data units or properties required to configure the decoder and

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
decode an image tile shall be declared in the decoder configuration and initialization properties associated
with the image item.
The reconstructed image of the associated image item is formed from one or more image tiles in a given grid
order within a larger canvas.
The image tiles corresponding to the extents are inserted in row-major order, top-row first, left to right, in
the order of the extents for the associated image item within the ItemLocationBox. The value of extent_count
within the ItemLocationBox shall be equal to (1+rows_minus_one)*(1+columns_minus_one). All image tiles
shall have exactly the same width and height, image_tile_width and image_tile_height. The reconstructed
image is formed by tiling the image tiles into a grid with a column width equal to image_tile_width and
a row height equal to image_tile_height, without gap or overlap. The grid of image tiles shall completely
“cover” the reconstructed image of the associated image item, where image_tile_width*columns is greater
than or equal to image_width and image_tile_height*rows is greater than or equal to image_height, where
image_width and image_height are signalled in the ImageSpatialExtentsProperty associated with the
image item.
The flags field is used to signal image tiles related information. The following flags values are defined.
0x000001 field_length_flag: when set to 1 specifies that the length of the fields image_tile_width and
image_tile_height is 32 bits. When field_length_flag is set to 0 specifies that the length of the fields
image_tile_width and image_tile_height is 16 bits.
0x000002 tile_config_info_present_flag: when set to 1, specifies that the decoder configuration data
needed to decode each extent independently is present in the ConstrainedExtentsGridProperty.
When tile_config_info_present_flag is set to 0, all data units or properties required to configure
the decoder and decode the extent independently shall be declared in the decoder configuration and
initialization properties associated with the image item.

6.5.41.2  Syntax
aligned(8) class ConstrainedExtentsGridProperty
extends ItemFullProperty('cexg', version = 0, flags) {
// this is a temporary,non-parsable variable
unsigned int FieldLength = ((flags & field_length_flag) + 1) * 16;
unsigned int(16) rows_minus_one;
unsigned int(16) columns_minus_one;
unsigned int(FieldLength ) image_tile_width;
unsigned int(FieldLength ) image_tile_height;

if(flags & tile_config_info_present_flag){
ExtentDecoderConfigurationRecord() extent_config;
}
}
6.5.41.3  Semantics
image_tile_width, image_tile_height: specify respectively the width and height in pixels of the image tiles.
rows_minus_one, columns_minus_one: specify the number of rows of image tiles, and the number of image
tiles per row. The value is one less than the number of rows or columns respectively. Image tiles enclosed
in extents populate the top row first, followed by the second row and following rows, in the order of
extents.
ExtentDecoderConfigurationRecord is the decoder configuration record needed to decode the corresponding
extents. The decoder configuration record is specific and defined by the image coding format used for
encoding the extent data.
© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
6.5.42  Disparity adjustment information
6.5.42.1  Definition
'dadj'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per associated No
identifier value):
Quantity (per associated At most one
identifier value):
The disparity adjustment descriptive item property defines the suggested global disparity adjustment
amount for a stereo pair.
This item property should only be associated with an item or entity group that describes a stereo pair. If
associated with a stereo pair entity group, the FileTypeBox or the ExtendedTypeBox associated with the
FileTypeBox shall indicate that the requirements of the 'unif' brand apply in the file.

6.5.42.2  Syntax
aligned(8) class DisparityAdjustmentProperty
extends ItemFullProperty('dadj', version = 0, flags = 0) {
signed int(32) disparity_adjustment;
}
6.5.42.3  Semantics
disparity_adjustment in units of 1/10 000 image widths. Positive values denote increased disparity with
respect to parallel view direction.
6.5.43  Stereo aggressors
6.5.43.1  Definition
'stag'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per associated No
identifier value):
Quantity (per associated Zero or more
identifier value):
The stereo aggressors descriptive item property specifies the presence and characteristics of stereo
aggressors detected within a stereo pair. Stereo aggressors are identified as elements that potentially cause

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
discomfort when viewing the stereo pair on a stereoscopic display. This item property allows to identify and
characterize these aggressors in detail.
This item property, when present, shall be used with an image item or an entity group that represents a
stereo pair. It can also be associated with other items not representing a stereo pair only if those items also
belong to a stereo pair entity group so it is clear in which stereo context it applies. If associated with a stereo
pair entity group ('ster' or 'stem'), the 'unif' brand shall be present in the compatible brands.
If this item property is associated with another item in addition to the stereo pair entity group, it serves as
a hint that the aggressors described by the property are localized to that specific item. For example, this can
be used to indicate that a "Lens occlusion" is present in only the left or right image item, or using a region
item, in a specific region of an image item. Multiple stereo aggressor properties may be associated with the
same image item or entity group representing a stereo pair since not all aggressors may be localized to the
same area.
NOTE 1 An image item can be associated with multiple stereo pair entity groups; however a stereo aggressor can
only apply to a specific entity group, which is why there is a requirement that the stereo aggressor has to be associated
with a stereo pair entity group.
NOTE 2 As localization of the stereo aggressors is indicated with item property associations, all stereo aggressors
within a single 'StereoAggressorsProperty' box need to share the same localization. Specifying multiple unique
localizations requires using multiple 'StereoAggressorsProperty' boxes.
The aggressor_severity shall be interpreted as follows:
— A value of 0 indicates an unknown severity. The file creator has no recommendation for the reader.
— A value of 1 to 42 (inclusive) indicates a mild severity. The file creator recommends that sensitive viewers
are warned about potential discomfort when viewing in stereo.
— A value of 43 to 84 (inclusive) indicates a medium severity. The file creator recommends that all viewers
are warned about potential discomfort when viewing in stereo.
— A value of 85 to 127 (inclusive) indicates a high severity. The file creator recommends that all viewers are
warned about potential discomfort when viewed in stereo and that viewing should default to monoscopic
rather than stereoscopic display unless overridden by the viewer.
If sub_type_uri is not specified for a specific aggressor, the aggressor_severity is a relative measure only
used to provide the viewer recommendations above and to rank the aggressors in the file relative to each
other. If sub_type_uri is specified for an aggressor, aggressor_severity shall be an absolute measure that
can be compared between files.

6.5.43.2  Syntax
aligned(8) class StereoAggressorsProperty
extends ItemFullProperty('stag', version = 0, flags = 0) {
unsigned int(8) aggressor_count_minus_one;
for(int i = 1; i <= aggressor_count_minus_one + 1; i++) {
unsigned int(8) aggressor_type;
unsigned int(1) sub_type_present;
unsigned int(7) aggressor_severity;
if (sub_type_present) {
utf8string sub_type_uri;
}
}
}
6.5.43.3  Semantics
version shall be equal to 0.
aggressor_count_minus_one is the number of aggressors minus one.

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
aggressor_type has the values defined in Table 1.
aggressor_severity provides an indication of how severe the file creator considers the aggressor to be.
If sub_type_uri is not defined, the severity is file-relative and can not be used to compare aggressor
severities between files.
sub_type_uri is an optional null-terminated UTF-8 character string of the Uniform Resource Identifier
(URI) used to more explicitly identify the type of the stereo aggressor as well as how to interpret
the aggressor_severity. If specified, the aggressor_severity shall be an absolute metric that can be
compared between files. If not present, it defaults to the empty string.
Table 1 — Defined aggressor_type values and their meaning
aggressor_type Meaning
0 Unspecified
1 Lens occlusion
2 Image condition mismatch (lighting conditions, colour,
glare, sharpness, processing differences)
3 Stereo window violation
4 Object(s) too close
5 Stereo calibration error(s)
6 Temporal alignment mismatch
7 Poor image quality in one or both views (e.g. due to spe-
cific noise patterns)
8 - 255 Reserved
6.5.44  Reference viewing environment
6.5.44.1  Definition
'reve'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one

The reference viewing environment applies to display-viewing colorimetry, not to scene-referred
colorimetry. It specifies the luminance and chromaticity parameters for the “surround” and “periphery”
of the display. The “surround” is the area surrounding a display that can affect the adaptation of the eye,
typically the wall or curtain behind the display, while “periphery” is the remaining environment outside of
the surround.
6.5.44.2  Syntax
class ReferenceViewingEnvironmentBox extends ItemFullProperty('reve', 0, 0){
unsigned int(32) surround_luminance;
unsigned int(16) surround_light_x;
unsigned int(16) surround_light_y;
unsigned int(32) periphery_luminance;
unsigned int(16) periphery_light_x;
unsigned int(16) periphery_light_y;
}
© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
6.5.44.3  Semantics
surround_luminance specifies the luminance of the surround in units of 0.0001 candelas per square metre.
surround_light_x and surround_light_y specify the normalized x and y chromaticity coordinates,
respectively, of the environmental reference surround light in the nominal viewing environment. These
parameters are according to the CIE 1931 definition of x and y as specified in ISO 11664-1 (see also
ISO 11664-3 and CIE 15) and are in normalized increments of 0.0001. The values of surround_light_x
and surround_light_y shall be in the range of 0 to 10000, inclusive.
periphery_luminance specifies the luminance of the periphery in units of 0.0001 candelas per square metre.
periphery_light_x and periphery_light_y specify the normalized x and y chromaticity coordinates,
respectively, of the environmental reference periphery light in the nominal viewing environment. These
parameters are according to the CIE 1931 definition of x and y as specified in ISO 11664-1 (see also
ISO 11664-3 and CIE 15) and are in normalized increments of 0.0001. The values of periphery_light_x
and periphery_light_y shall be in the range of 0 to 10 000, inclusive.
6.5.45  Nominal diffuse white
6.5.45.1  Definition
'ndwt'
Box type:
Property type: Descriptive item property
ItemPropertyContainerBox
Container:
Mandatory (per item): No
Quantity (per item): At most one

6.5.45.2  Syntax
class NominalDiffuseWhiteBox extends ItemFullProperty('ndwt', 0, 0){
unsigned int(32) diffuse_white_luminance;
}
6.5.45.3  Semantics
diffuse_white_luminance indicates the default nominal diffuse white luminance in units of 0.0001 candelas
per square metre. The chromaticity information associated with the diffused white luminance is the
same as the chromaticity information specified in the ColourInformationBox of the associated image. If
diffuse_white_luminance is set to 0 then the default definition of the ISO/TS 22028-5 should be used.

Subclause 6.6
Subclause 6.6.1
Replace:
The number of SingleItemTypeReferenceBoxes with the box type 'dimg' and with the same value of from_
item_ID shall not be greater than 1.

With:
The number of SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge entries with the box
type 'dimg' and with the same value of from_item_ID shall not be greater than 1.

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)

Subclause 6.6.2.2.1
Replace:
The input images are listed in the order they are layered, i.e. the bottom-most input image first and the top-
most input image last, in the SingleItemTypeReferenceBox of type 'dimg' for this derived image item within
the ItemReferenceBox.
With:
The input images are listed in the order they are layered, i.e. the bottom-most input image first and the top-
most input image last, in the SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge of type
'dimg' for this derived image item within the ItemReferenceBox.

Subclause 6.6.2.2.3
Replace:
reference_count is obtained from the SingleItemTypeReferenceBox of type 'dimg' where this item is
identified by the from_item_ID field.

With:
reference_count is obtained from the SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge
of type 'dimg' where this item is identified by the from_item_ID field.

Subclause 6.6.2.3.1
Replace:
The input images are inserted in row-major order, top-row first, left to right, in the order of
SingleItemTypeReferenceBox of type 'dimg' for this derived image item within the ItemReferenceBox. In
the SingleItemTypeReferenceBox of type 'dimg', the value of from_item_ID identifies the derived image
item of type 'grid', the value of reference_count shall be equal to rows*columns, and the values of to_item_
ID identify the input images.
With:
The input images are inserted in row-major order, top-row first, left to right, in the order of
SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge of type 'dimg' for this derived image
item within the ItemReferenceBox. In the SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge
of type 'dimg', the value of from_item_ID identifies the derived image item of type 'grid', the value of
reference_count shall be equal to rows*columns, and the values of to_item_ID identify the input images.

Subclause 6.11.1
Replace:
The number of SingleItemTypeReferenceBoxes with the box type 'drgn' and with the same value of from_
item_ID shall not be greater than 1.

© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)

With:
The number of SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge entries with the box
type 'drgn' and with the same value of from_item_ID shall not be greater than 1.

Subclause 6.6.2.3
Add the following new subclauses after subclause 6.6.2.3:
6.6.2.4  Tone-map derivation
6.6.2.4.1  Definition
An item with an item_type value of 'tmap' defines a derived image item whose reconstructed image is formed
from one base input image and a secondary input image that will be referred to as a gain map input image.
The input images are given by the SingleItemTypeReferenceBox/ SingleItemTypeReferenceBoxLarge of
type 'dimg' for this derived image item within the ItemReferenceBox. In the SingleItemTypeReferenceBox/
SingleItemTypeReferenceBoxLarge of type 'dimg', the value of from_item_ID identifies the derived image
item of type 'tmap', the value of reference_count shall be equal to 2, and the values of to_item_ID identify
the input images, of which the first shall be the base input image and the second shall be the gain map input
image. The gain map input image may have different dimensions than the base as documented in ISO 21496-1.
Reconstruction is done by applying the gain map to the base image according to the algorithm described in
ISO 21496-1. As further described in ISO 21496-1, the gain map may be scaled by a weight during application
in order to adjust for local viewing conditions.
The base input image item shall be associated with a 'colr' item property. This corresponds to the baseline
image colorimetry metadata described in ISO 21496-1.
The gain map input image item shall be associated with a 'colr' item property of type 'nclx' which
indicates any transformations that the encoder has done to improve compression. In this item property,
colour_primaries and transfer_characteristics shall be set to 2. The full_range_flag may be set to
either 1 or 0. If the full_range_flag is 0, the reader shall clip the gain map pixel values to the logical range
0.0 to 1.0 after applying matrix_coefficients and full_range_flag.
A 'tmap' derived image item shall be associated with a 'colr' item property. This corresponds to the
alternate image colorimetry metadata described in ISO 21496-1, which describes the colour properties of
the reconstructed image if the gain map input item is fully applied (i.e. with a weight of 1.0 or -1.0 depending
on the gain map metadata).
When a 'tmap' derived image item is the input to another derived image item, that derived image item shall
treat the reconstructed image of the 'tmap' derived image item as if the gain map has been fully applied and
has the colour properties of the 'colr' item property associated with the 'tmap' derived image item.
The base input image and the 'tmap' derived image item should be associated with 'clli' item properties
as appropriate to further document the optimal viewing conditions of each representation.
A 'tmap' derived image item should be associated with a PixelInformationProperty item property. This
property provides a hint to decoders on the approximate amount of colour resolution available after fully
applying the gain map.
The number of channels in the gain map input item may be different than the number of channels in the
gain_map_metadata in the body of the 'tmap' derived image item. If the gain map input item is single channel
while the gain_map_metadata signals multi-channel, the gain map input item shall be treated as if it has three
identical colour channels. If the gain map input item is multi-channel while the gain_map_metadata signals
single channel, the gain_map_metadata shall be treated as if it is multi-channel with identical values for all
channels.
© ISO/IEC 2025 – All rights reserved
ISO/IEC 23008-12:2025/Amd. 1:2025(en)
The gain map input image should be marked as hidden by setting (flags & 1) equal to 1 in its ItemInfoEntry.
The requirements of the 'tmap' brand defined in subclause 10.2.6 apply to any file containing a tone-map
derived image item.
NOTE 1 Backwards compatibility with parsers that do not support the tone-map derivation can be achieved by
placing the base input image item and the 'tm
...