[Cin] Some tests on blending

[Phyllis Smith]

Checked into source GIT, the tone mapping SYSLIB blend program plugin
addition from Andrea.
Checked into manual GIT, the attached tex file changes  for HDR/clipping
stuff exactly as provided by Andrea.
Appended Examples.txt to add Example 6 tone mapping description exactly as
provided by Andrea.
(Andrea, please verify correctness in case I made a mistake).  Thank you.

On Wed, Apr 2, 2025 at 2:32 AM Andrea paz <gamberucci.andrea at gmail.com>
wrote:

> I have included some small adds in the manual that deal with HDR. See
> if they fit. There would also be to change the Blend Algebra examples
> file written by Georgy.
>
> [Part to append to the file
> https://cinelerra-gg.org/download/testing/BlendPluginExamples/Examples.txt
> ]:
>
>
> Example 6.
> ----------
>
> To tonemapping an HDR media and report its values within the range (0,
> 1.0):
>
> BLEND_PROGRAM_INIT
>
> COLORSPACE_RGB
> PARALLEL_SAFE
>
> BLEND_PROGRAM_PROC
>
> float mult;
>
> mult = KEY_A-0.5;
> if (mult >= 0) mult = 1+mult*10;
> else mult = 1/(1-mult*10);
>
> R(0) = R(0)*mult;
> G(0) = G(0)*mult;
> B(0) = B(0)*mult;
>
> BLEND_PROGRAM_END
>
>
> First attach this blend program to your track above the other plugin
> which you want to make not to clip. Switch clipping off in the blend
> program dialog. This blend program will use the alpha slider (which
> can have the value between 0.0 and 1.0) in the following manner:
>
> 0.5 (exactly in the middle): no RGB change
> 0.6: R,G,B are multiplied by 2
> 0.7: multiplied by 3
> ...
> 1.0: multiplied by 6
> 0.4: multiplied by 1/2 (i.e. divided by 2)
> 0.3: multiplied by 1/3
> ...
> 0.0: multiplied by 1/6 (divided by 6)
>
> If you set it, for example, to 0.4 here, your R,G,B values will be
> divided by 2, so that the color values up to 2.0 will be scaled down
> into the clip range. If you can have values up to, let's say, 5.0,
> then set the alpha slider to 0.1 to scale down by 5, etc.
>
> Then attach the plugin you need to work unclipped, your histogram or
> whatever. Pay attention that all the color values your plugin gets
> now, are scaled down uniformly.
>
> Then attach the same blend program once more, under your needed
> plugin. This time set the alpha slider to 0.6 (if it is 0.4 in the
> upper one), or to 0.9 (if the upper one is 0.1), i.e. displace it from
> the middle in the opposite direction. The unclipped values coming from
> your working plugin will be scaled back by the same amount.
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cinelerra-gg.org/pipermail/cin/attachments/20250402/48faa61d/attachment.htm>