On Thu, 3 Apr 2025, Andrea paz wrote:
OK, I understand your explanation. Just one point: does it only apply to plugins that refer to color spaces (which by definition are limited (0, 1))? Or does it apply to all, e.g., Histogram and the like? Another question: generally conversions between color spaces are referred to CMS, i.e. via ICC color profiles; OpenColorIO; ACES, etc. Since CinGG does not have CMS how does the Color Space plugin work? And how does the \u201cYUV Color Space\u201d tool in \u201cPreferencies\u201d work?
An immanent property of a pixel is its color. All pixels have some color. If there is some video in a clip (not only audio), it consists of video frames, and each frame consists of pixels, and each pixel has some color. Color is expressed as at least 3 values (usually 3 but it may be more) in some coordinate system. This color coordinate system composes a color space. Some color space always exists. If some plugin alters only geometry (changes X and Y coords of pixels but does not change colors), it still works in some color space, but in this case the particular color space does not matter as pixel colors remain constant. If some other plugin changes colors or in some way accounts for colors, it almost always must bear in mind the color coordinate system, the color space pixels are in. Not just color perception CMS and ICC profiles are for, but more fundamental. Not all color spaces are limited to 0..1. For example, in YUV only Y is 0..1, U and V are -0.5 .. +0.5, while in HSV H is 0..360. Should you calculate an Hue histogram in HSV color space (why not?), you must take into account the particular range of Hue. Despite Hue has no ICC profile. An MP4 video color space is some kind of YUV. If you wish to apply, let's say, Chromakey, the latter works in HSV space. Therefore, you have to convert pixels from YUV to HSV making use of some mathematical equations for coordinate transformations. The Color Space conversion plugin also uses some equations to do the job. If you wish to extend it to a broader range to perform similar transformations for HDR, you have to write the corresponding mathematical equations. But as soon as you have the equations, you can easily express them in form of one more blend program function, and you will have your HDR transformation working. _______________________________________________________________________________ Georgy Salnikov NMR Group Novosibirsk Institute of Organic Chemistry Lavrentjeva, 9, 630090 Novosibirsk, Russia Phone +7-383-3307864 Email [email protected] _______________________________________________________________________________