Commit 0c6691cb authored by Pekka Paalanen's avatar Pekka Paalanen
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glossary: add color volumes


Signed-off-by: Pekka Paalanen's avatarPekka Paalanen <pekka.paalanen@collabora.com>
parent ff1f5fff
Pipeline #518447 passed with stage
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---
SPDX-FileCopyrightText: 2020 Collabora, Ltd.
SPDX-FileCopyrightText: 2020-2021 Collabora, Ltd.
SPDX-License-Identifier: MIT
---
......@@ -29,6 +29,29 @@ color channel as well.
A tuple of numbers, representing a color in some color system. Each
element in the tuple is a [color channel](#color-channel) value.
#### color volume
A three dimensional space of [color value](#color-value)s. This
includes both "color" (e.g. hue and saturation) and brightness
(luminance).
#### container color volume
This is the color volume addressable by a given signal container format
([pixel format](#pixel-format), encoding, defining color space). An
example is BT.2020/PQ as is standard for driving many consumer HDR
monitors.
As a special case, the container color volume with floating-point
[pixel format](#pixel-format)s is practically infinite, because
negative and greater than 1.0 values can be represented. The defining
color space and dynamic range are likely anchored to channel values 0.0
and 1.0, but due to extrapolation the representable color volume is not
limited by these. The target color volume needs to be specified
separately.
See also: [target color volume](#target-color-volume)
#### image
Conceptually a two-dimensional array of [pixel](#pixel)s. The pixels
......@@ -85,6 +108,22 @@ In [DRM](#DRM) [KMS](#KMS):
* A hardware composition element capable of holding one framebuffer
([image](#image)) and having position and stacking order on screen.
#### target color volume
The color volume intended to be usable by a given video or image
signal. That is, the signal has been produced targeting this color
volume in the mastering process. An example is using HDR static
metadata (SMPTE ST 2086) to describe the image content when the
container is BT.2020/PQ.
Traditional container formats and ICC v2-v4 profiles assume that
container color volume equals target color volume. This makes the most
use of the pixel storage. Using target color volume smaller than the
container color volume means that some code points will never be used,
which is wasteful for storage.
See also: [container color volume](#container-color-volume)
#### Wayland
A window system protocol.
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