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The CameraConfiguration::validateColorSpaces() function performs color
space validation on a camera configuration, by validating the color
space of each stream individually, and optionally ensuring that all
streams share the same color space. The individual validation is very
basic, limited to ensuring that raw formats use a raw color space.
Color spaces are more constrained than that:
- The Y'CbCr encoding and quantization range for RGB formats must be
YcbcrEncoding::None and Range::Full respectively.
- The Y'CbCr encoding for YUV formats must not be YcbcrEncoding::None.
Instead of open-coding these constraints in the validateColorSpaces()
function, create a new ColorSpace::adjust() function to centralize color
space validation and adjustment, and use it in validateColorSpaces().
Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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Rectify the ColorSpace::Srgb to denote that it does not use
any Y'Cbcr encoding and uses full range.
The kernel on the other hand, recommends to use Rec601 as the encoding
for V4L2_COLORSPACE_SRGB. It is not very explicit but it can be
inferred that the kernel assumes V4L2_COLORSPACE_SRGB is a YUV-encoded
one. However, when the data is in RGB, no encoding is required (and
this is denoted by YcbcrEncoding::None in libcamera).
Hence, to be clear on the libcamera colorspace API, rectify the
ColorSpace::Srgb preset to use YcbcrEncoding::None and full range.
Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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Add a ColorSpace:fromString() function to parse a string into a color
space. The string can either contain the name of a well-known color
space, or four color space components separate by a '/' character.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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Sort the members of the ColorSpace class in color_space.cpp to match the
color_space.h order. No functional change intended.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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The JPEG color space is badly name, as the JPEG specification (ITU-T
T.81) doesn't define any particular color space:
The interchange format does not specify a complete coded image
representation. Application-dependent information, e.g. colour
space, is outside the scope of this Specification.
The JFIF specification (ITU-T T.871) is clearer as it requires ITU-R
BT.601 YCbCr encoding and a full quantization range:
The interpretations of Y, CB, and CR are derived from the E'Y, E'Cb,
and E'Cr signals defined in the 625-line specification of Rec. ITU-R
BT.601, but these signals are normalized so as to permit the usage of
the full range of 256 levels of the 8-bit binary encoding of the Y
component.
It however doesn't specify color primaries or a transfer function
explicitly. It only mentions the latter when describing the conversion
from YCbCr to RGB:
The inverse relationship for computing full scale 8-bit per colour
channel gamma pre-corrected RGB values (following Rec. ITU-R BT.601
gamma pre-correction and colour primary specifications) from YCbCr
colours (with 256 levels per component) can be computed as follows:
[...]
Given that ITU-R BT.601-5 (1995) didn't specify color primaries or a
transfer function, and that the later ITU-R BT.601-7 (2011) version
specifies color primaries for the 625-line variant that do not match
sRGB, the JPEG color space in libcamera is badly named. This is
confirmed by ITU-T T.871:
As this Recommendation | International Standard is based on the prior
informally-circulated JFIF version 1.02 specification that was
produced in 1992, which referenced Rec. ITU-R BT.601 (formerly CCIR
601), it references that specification for definition of the E'Y,
E'Cb, and E'Cr signals that correspond to the YCBCR values specified
herein. However, since the development of the prior JFIF version 1.02
specification, additional industry specifications have been developed,
Rec. ITU-R BT.601 has been updated, and common industry practice has
emerged which often follows the sYCC specification in IEC
61966-2-1/Amd.1. The difference between the use of the colour
interpretation specification in this Recommendation | International
Standard and that of the sYCC specification may be considered
negligible in practice.
Rename the color space to sYCC, as its definition matches the sYCC
standard, and indicate that it is typically used to encode JPEG images.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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s/Raspberry Pi (Trading) Limited/Raspberry Pi Ltd/ to reflect the new
Raspberry Pi entity name.
Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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This class represents a color space by defining its color primaries,
the transfer (gamma) function it uses, the YCbCr encoding and whether
the output is full or limited range.
Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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