*Contact email:*
[email protected]

*Explainer:* None
*Specification:* None

*Summary:*
These fields were accidentally exposed to the web in crrev.com/562990 by
way of crrev.com/427153. They are not part of any specification.

These fields allow OffscreenCanvas::convertToBlob to specify a target color
space (srgb, display-p3, and rec2020) and pixel format (uint8 and uint16).
This sets a default behavior of setting the color space sRGB and pixel
format of 8 bits per pixel.

When these parameters are removed, the target space for convertToBlob will
default to the color space of the canvas (srgb or display-p3), and the
pixel format will default to the pixel format of the canvas (uint8 is the
only supported pixel format).

*Motivation:*
The behavior caused by these fields at odds with the HTML specification,
section "Serializing bitmaps to a file", which says that

For image types that support color profiles, the serialized image must
include a color profile indicating the color space of the underlying bitmap.


For example, for a Display P3 canvas, calling convertToBlob with no
arguments should result in a blob that specifies a Display P3 color profile.

These fields can only degrade the quality of the resulting image, compared
with the behavior from the HTML specification.

*TAG review:* N/A

*Risks:*
When this feature is removed, the images resulting from convertToBlob are
guaranteed to be an equal or higher fidelity representation as compared
with behavior before this feature was removed, because all OffscreenCanvas
elements are 8-bit sRGB or Display P3.

*Interoperability and Compatibility*
Gecko: Never implemented
WebKit: Never implemented
Web developers: No signals

*Debuggability:* N/A

*Is this feature fully tested by web-platform-tests?*
No, there exists one Blink layout test for this feature.

*Tracking bug:* crbug.com/1384538

*Link to related intents: *
This was discovered when writing tests for Canvas Floating Point Color Types
<https://chromestatus.com/feature/5086141338877952>, which is a
prerequisite for High Dynamic Range Support for HTMLCanvasElement
<https://chromestatus.com/feature/5703719636172800>.

Link to entry on the Chrome Platform Status
<https://chromestatus.com/feature/5129184450445312>

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