[PD] [Gem] bit depth of display

Claude Heiland-Allen claude at mathr.co.uk
Thu Feb 17 20:30:07 CET 2022

Hi Roman,

On 17/02/2022 17:59, Roman Haefeli wrote:
> the gradients between the
> pixels shows edges that look like low bit depth (and probably are due
> low bit depth).
No clue about high bit depth output. Possible workaround: a shader that 
does dithering could help mask the problem, that is if the OpenGL 
texture interpolation is not the source of the problem (hopefully it's 
done with floats, if not maybe you can do interpolation in the shader 
too after reading the texels without interpolation).  Check the OpenGL 
specification for GL_LINEAR magnification filter details, maybe it says 
how much precision is guaranteed.

One thing you could do to diagnose is check pixel values of neighbouring 
bands to see if they are off by one (in which case suspect needing 
higher bit depth output) or more (in which case suspect OpenGL GL_LINEAR 
precision being insufficient).


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