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Re: [Public WebGL] The Newly Expanded Color Space Issue
On 09/09/2010 05:28, Vladimir Vukicevic wrote:
The mathematics of the conversion are the same. Only the values
change. Converting from image space to linear or from image space
to sRGB instead of image space to display space won't change the
complexity of the code which, in the general case between 2 ICC
profiles, is a 4x4 matrix transform.
----- Original Message -----
Actually, I think a better option for WebGL 1.0 would be to do the simplest thing possible -- for choice 1, that would be to have a boolean flag that says "do whatevever gamma correction/colorspace conversion/etc. the browser normally does on images before uploading" or "don't touch the pixels at all". Doing anything else seems extremely painful to define, and will likely require some pretty instrusive work in the engines to get the conversions right. The piece that I think that we need for WebGL 1.0 is the "off" switch, that is ensuring that you can get raw uncorrected data from images.
In the likely rough conversion browsers currently do, it is just a
case of using a different exponent in the power function.
The pieces of the Canvas2D and CSS spec's quoted in this thread say
For choice 2, the simplest option would be to define the output canvas to always be sRGB (as with CSS) and leave it at that;
These specs do not say that processing of the Canvas2D drawings or
web page blending must be done in an sRGB space.
- CSS colors are specified in sRGB
- Canvas2D processing shall be done in the same color space used
for CSS processing
- getImageData/putImageData return/accept colors specified in
As Steve Baker said, we need to be honest. This is a necessary step
to correctly specified extensions now and in the future. For
example, if we claim the canvas is sRGB how do we later explain the
purpose of FRAMEBUFFER_SRGB?
no way to modify this, and to not do any conversion; just assume that the pixels that are written are sRGB. This is what the 2D canvas does, with getImageData/putImageData (with an unfortunate alpha premultiplication step).
Future extensions could add more specific conversions/getContext parameters, but I don't think they're needed in 1.0
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