bilinear point in percents

[anthony]

Hmmm looking at IMv6 code... I don't see any conversions of pixel coordinates to image coordinates for the calculations!
That seems to indicate that I have only been using pixel coordinates for sparse color lookup!

Same is the case for IMv7.


Looks like it is a major mistake in the code from the start for sparse color, Probably an initial error that while fixed for distort was never fixed for sparse color. It is strange that I just never notice that it was wrong in my examples for perfect gradients!
But then I was concentrating on white, not black in those examples.

So the question becomes... Should sparse color use pixel coordinates or image coordinates?
For this operation pixel coordinates may work better.

[fmw42]

So Fred will it break anything of yours if I fix it now. And it probably should be fixed

I don't think it will make much difference in my scripts. Only 4 are affected. Let me know whenever they are fixed (no rush) in a beta and I will double check and make mods as needed.

[anthony]

Note certain I will fix... More often than not for sparse color, you are actually wanting to set specific pixels specific colors. Its purpose was to generage more '2-dientional freeform' gradients, than was otherwise posible. basically gradients that was being generated using slow FX expressions.

Which is why I posed the question, rather than just directly fix it.

It just means I need to adjust the 'perfect gradient' examples. Though really the example are not really wrong, just not described correctly. I also will have to specifically point out that it uses pixel coordinates, and not image coordinates are distort uses.

This does not mean I will change distort. It really does need to use image coordinates.

This does not mean I don't want to add some special 'hole-filling' morphology functions (like color-diffusion). Which needs a 'mask' or at least a 'alpha mask', or even a 'read-protect mask' as part of its handling.

[fmw42]

This does not mean I don't want to add some special 'hole-filling' morphology functions (like color-diffusion). Which needs a 'mask' or at least a 'alpha mask', or even a 'read-protect mask' as part of its handling.

I think a more useful approach would be inpainting. There is free code available. Not sure of the licensing issues. But see viewtopic.php?f=22&t=23795#p101042

[anthony]

Note certain I will fix... More often than not for sparse color, you are actually wanting to set specific pixels specific colors. Its purpose was to generage more '2-dientional freeform' gradients, than was otherwise posible. basically gradients that was being generated using slow FX expressions.

After much deliberation, I decided to leave sparse color using 'pixel coordinates' and just fix the sparse color 'mathematical gradient' examples.
http://www.imagemagick.org/Usage/canvas ... _gradients

This has now been done. Changes should appear soon.