[FFmpeg-devel] [RFC] Scalar color conversion utils (colorutils.[hc])?

[Stefano Sabatini]

Hi all,

the need for such a facility mainly arises for libavfilter filters.
For example we may need something to work like this:

pad=padcolor=COLOR

or

drawbox=X:Y:COLOR

and many other filters as well may need to take in input a textual
representation of a color and convert it to a given colorspace.

libavcodec/colorspace.h defines some useful macros for converting from
RGB to YUV, but I think what we need here is a convenient API of the form:

int av_parse_color(uint16_t color[4], enum PixelFormat dst_pix_fmt, const char *color_string, void *log_ctx)

and 

int av_convert_color_to(uint16_t *dst_color[4], enum PixelFormat dst_pix_fmt, 
                       (uint16_t *src_color[4], enum PixelFormat src_pix_fmt,
                        void *log_ctx);

Support for HSV colorspace could be provided defining an HSV pixel format.

Some of the questions which need a response:

* We may need a table containing all the colornames <-> color.  In
  which colorspace should be specified the color? (An RGB32 variant
  could be the ideal solution.)

* Where it should be implemented? lavfi or lsws seem the better
  candidates.

* How should be done the color-spec string? It may contains a simple
  name but also a color specifications. Variants which come to mind:
  rgb=RR:GG::BB, hsv=HH:SS:VV, yuv=YY:UU:VV.

Regards.
-- 
FFmpeg = Foolish and Fast Mastering Proud Epic God