[Cin] Fwd: cingg vs gimp 2.10 compositing mode divide

[Andrew Randrianasulu]

вс, 30 окт. 2022 г., 17:21 Phyllis Smith <phylsmith2017 at gmail.com>:

> The below  is very possible (except for the gimp comparison) meaning we
> may be making black where it should be white.  But as Andrew implied old
> projects may suddenly provide different unexpected results if we change it.
>
>> I think you see, we are making black areas where gimp was making white
>> areas...
>>
>


or may be i get layers order wrong /



> Much work was performed to follow one of many versions of the Overlays
> from various other software packages.  In the Description section of the
> Overlays chapter in the manual, it states:
> Divide: Divides source color by destination color. If the source color is
> white, the
> result color is the underlying color. The resulting image is often
> lighter.
> *Mathformula used is different than that used by Gimp*; there is no SVG
> equivalent.
> https://cinelerra-gg.org/download/CinelerraGG_Manual/Arithmetic_Group.html
>
> I believe that CinGG when rewriting the code several years ago attempted
> to follow the algorithm that currently existed in Cinelerra HV version at
> the time, but the image I had included earlier comparing CinGG with HV
> 4.6.1 is so different.  One or the other is inconsistent.  Changing it to
> match Gimp is not desirable, however it would be great to fix an obvious
> bug.
>

I found some python description of Adobe's blend modes .... also, blending
and compositing can be two stages of more complex process??

https://github.com/psd-tools/image-blender/blob/master/src/image_blender.pyx


see divide/subtract grouped together ...



> On Sun, Oct 30, 2022 at 1:59 AM Andrew Randrianasulu via Cin <
> cin at lists.cinelerra-gg.org> wrote:
>
>> but should we blindly  follow gimp ? Again, gimp tend to have bigger mode
>> list ) may be right thing to do  is leave some of our modes intact (they
>> might be buggy but graphics art can utilize that, too) and add
>> gimp/svg/oldcin compatible modes ?
>>
>
>
>>
>> ---------- Forwarded message ---------
>> От: Андрей Рандрианасулу <randrik at mail.ru>
>> Date: сб, 29 окт. 2022 г., 18:43
>> Subject: cingg vs gimp 2.10 compositing mode divide
>> To: randrianasulu <randrianasulu at gmail.com>
>>
>>
>>
>> I think you see, we are making black areas where gimp was making white
>> areas...
>> --
>> Андрей  Рандрианасулу
>> --
>> Cin mailing list
>> Cin at lists.cinelerra-gg.org
>> https://lists.cinelerra-gg.org/mailman/listinfo/cin
>>
>
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