Yaron,
just some questions back to you:
Relying on OpenGL's output means most of the time to be dependent on
hardware. While the idea is very nice to let the GPU perform the PCS alpha
blending, are you shure reading from a texture is not a performance
bottleneck?
Are all your supported plattforms able to handle your maximum precision?
Some grafics bords still support 8-bit only (possibly less?). This could
be too narrow for Lab rendering as Lab is pretty large. Colour stepping
could become visible in this case.
Converting to your canvas profile, whatever this means, at the last stage
should be ok, as all reandering is done before in your concept. So, whats
the problem here?
regards
Kai-Uwe Behrmann
+ development for color management
+ imaging / panoramas
+ email: [EMAIL PROTECTED]
+ http://www.behrmann.name
Am 05.12.06, 13:31 +0200 schrieb Yaron Tadmor:
> Hi,
>
> I'm pretty new to color management, and color profiles.
> I'm writing an application which allows to composite several images on a
> single canvas, and each image can have its own color profile. The global
> canvas also has a color profile (which is the color profile the final
> canvas image will be exported in).
>
> When blending the images I need to blend them in a single profile. The
> most appropriate is the canvas profile.
> Since I'm using openGL to render the layers, there's a problem when this
> profile is a CMYK profile. The problem is that openGL doesn't support
> CMYKA (or CMYK for that matter) so I need to split my rendering to 2
> parts (CMY and K), which slows down the GUI.
>
> I was wondering if I could somehow use a PCS (say LAB) to perform my
> blending. This way I can convert all input images to the PCS, load them
> to openGL as RGBA textures. Then I can render using openGL letting it do
> the alpha blending on this PCS, and then get the rendered image and
> convert to the canvas profile?
> Could this work?
>
> My main concern is that if the canvas profile is a narrow gamut profile,
> I might lose precision, since the PCS image data will need to be
> converted to unsigned chars in order to give to openGL.
>
> Am I making sense, or am I missing something?
>
> Thanx
> Yaron Tadmor
>
>
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