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Re: [Public WebGL] Gamma correction and texImage2D/texSubImage2D
On 06/09/2010 21:34, Chris Marrin wrote:
Why is it out of scope? Not doing so violates the PNG spec. I think
it is entirely reasonable to provide a way for the application to
give WebGL information about the gamma of the samples in the PNG
file. Allowing specification of physically linear vs. non-linear
covers 98% of use cases.
But we need to make an assumption if the incoming PNG image omits
any color space information. I think it is out of scope to add the
ability to let the author choose the color space for these images
as they are read in with texImage2D. So do we choose sRGB or
Conceptually the data is converted to physically linear but since
not losing data requires 12-bits per channel, a converted texture
needs more memory. So indeed the spec. recommends implementations do
the conversion as they read the texels. Filtering can then be done
using an enlarged number of bits. The end result is the same.
When using sRGB textures, GL converts the incoming texture
data to a physically linear space. When using sRGB
renderbuffers, GL converts the blended & multisampled
output to the perceptually-linear space of sRGB.
From my reading, incoming textures are not necessarily
converted. They may be converted when accessed to preserve more
of the color data. In fact, I think the spec recommends doing
that to preserve one of the advantages of using sRGB images, to
increase the resolution of the dark parts of an image. But I may
Sorry for my sloppy language.
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