[Cin] oops apparently 'subtract' mode is broken!

[Andrew Randrianasulu]

пн, 26 сент. 2022 г., 21:27 Phyllis Smith <phylsmith2017 at gmail.com>:

>
> may be Phyllis can replace our original red-green square  images with
>>>>> full-color gradients + photo, so effect will be more natural? Or add this
>>>>> into new appendix .....
>>>>>
>>>> Good idea to add in appendix but I am not sure I could get it right.
>>>
>>
>>
>> may be download images from said website via "download" button, then
>> place them on tracks and render single frame for each of those  30
>> different composition modes on top track? sorry if this sounds big, I can
>> try this idea  myself, just then I will generate whole folder of images for
>> you to pick up and integrate into manual. < oh Andrew, come on, you just
>> too lazy for even minimal work - my conscience >
>>
>
> It does sound big but quite interesting to me and not a problem with TeX
> editing.  I think I will have time in October to get serious and then have
> you proofread?
>


OK! looking forward to October then.


>> or you mean whole TeX editing? I should try to retest if my pdf
>> generating setup still work ....
>>
>>
>>
>>>
>>>> more documentation, it seems Adobe products use shared code for this
>>>> ....
>>>>
>>>>
>>>> https://www.rippletraining.com/blog/final-cut-pro-x/understanding-blend-modes-final-cut-pro/
>>>>
>>> Another good URL to look at.  When coding all of the Overlay modes,
>>> Porter Duff explanations and example were used as the basis.  Not sure if
>>> Gimp and PhotoShop use the same basis.
>>>
>>>>
>>>>
>>>> --quote---
>>>>
>>>> Subtract
>>>>
>>>> Subtract does what it advertises; the color values of one layer are
>>>> subtracted from the other layer. This tends to have a net darkening effect.
>>>> Pixel values can’t fall below zero, so negative numbers are rendered to
>>>> black.
>>>>
>>>>
>>>> ---end quote---
>>>>
>>>>
>>>> in older cingg code (from 4.6.mod era - earliest public code on Google
>>>> code) I see such construct :
>>>>
>>>>
>>>> /data/data/com.termux/files/home/cingg-g~nelerra-4.6.mod/cinelerra/overlayframe.C
>>>>      4762/69317  UTF-8        6%
>>>>
>>>>                         break; \
>>>>
>>>>                 case TRANSFER_SUBTRACT: \
>>>>
>>>>                         r = (temp_type)output[0] - (temp_type)input1; \
>>>>
>>>>                         g = ((temp_type)output[1] -
>>>> (temp_type)chroma_offset) - \
>>>>
>>>>                                 ((temp_type)input2 -
>>>> (temp_type)chroma_offset) + \
>>>>
>>>>                                 (temp_type)chroma_offset; \
>>>>
>>>>                         b = ((temp_type)output[2] -
>>>> (temp_type)chroma_offset) - \
>>>>
>>>>                                 ((temp_type)input3 -
>>>> (temp_type)chroma_offset) + \
>>>>
>>>>                                 (temp_type)chroma_offset; \
>>>>
>>>>                         if(r < 0) r = 0; \
>>>>
>>>>                         if(g < 0) g = 0; \
>>>>
>>>>                         if(b < 0) b = 0; \
>>>>
>>>>                         r = (r * opacity + output[0] * transparency) /
>>>> max; \
>>>>
>>>>                         g = (g * opacity + output[1] * transparency) /
>>>> max; \
>>>>
>>>>                         b = (b * opacity + output[2] * transparency) /
>>>> max; \                                                              break; \
>>>>
>>>>
>>>> ---
>>>>
>>>>
>>>> so it basically had specific guard against going negative. Not sure if
>>>> our implementation does the same just in different place?
>>>>
>>>>
>>>> I see no specific handling of it in macros ...
>>>>
>>>>
>>>>
>>>> overlayframe.h     [----] 38 L:[ 53+ 0  53/615] *(1572/17155b) 001[*][X]
>>>>
>>>> // ADDITION<--->[(Sa + Da), (Sc + Dc)]
>>>>
>>>> #define ALPHA_ADDITION(mx, Sa, Da) (Sa + Da)
>>>>
>>>> #define COLOR_ADDITION(mx, Sc, Sa, Dc, Da) (Sc + Dc)
>>>>
>>>> #define CHROMA_ADDITION COLOR_ADDITION
>>>>
>>>>
>>>> // SUBTRACT<--->[(Sa - Da), (Sc - Dc)]
>>>>
>>>> #define ALPHA_SUBTRACT(mx, Sa, Da) (Sa - Da)
>>>>
>>>> #define COLOR_SUBTRACT(mx, Sc, Sa, Dc, Da) (Sc - Dc)
>>>>
>>>> #define CHROMA_SUBTRACT COLOR_SUBTRACT
>>>>
>>>>
>>>> but apparently you can add some comparing here ...just .. it went from
>>>> two-stage process to single stage for untrained eye and I am not sure where
>>>> to put those ifs?
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> вс, 25 сент. 2022 г., 11:06 Andrew Randrianasulu <
>>>>> randrianasulu at gmail.com>:
>>>>>
>>>>>> I found Graphics-softlight mode behaving visually close...but not
>>>>>> sure how close to CinHV/CV subtract mode ...
>>>>>>
>>>>>>
>>>>>>
>>>>>> вс, 25 сент. 2022 г., 10:24 Andrew Randrianasulu <
>>>>>> randrianasulu at gmail.com>:
>>>>>>
>>>>>>> I was trying to repeat tuto at
>>>>>>>
>>>>>>> https://linuxvideoediting.blogspot.com/2022/01/transparent-text-effect-in-Cinelerra-part1.html?m=1
>>>>>>>
>>>>>>>
>>>>>>> so I loaded video, created empty new vid track, applied 'titles',
>>>>>>> 'blur' and 'invert video' to _empty track_, then set track's mode to
>>>>>>> subtract .... result was color inversion of original video on second vid
>>>>>>> track (
>>>>>>>
>>>>>>
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