blender - functionality for blending of image data using diofferent algorithms libAfterImage/blender.h

       Sasha Vasko <sasha at aftercode dot net>
       libAfterImage/colorspace

       blend_scanlines_name2func()  will  strip  leading  whitespaces  off  of  the supplied name, and then will
       attempt to match it against the list of names of merging functions. It will then return  pointer  to  the
       function  with  matching  name.   list_scanline_merging()  simply  prints  out description of implemented
       blending/merging methods onto the supplied stream, in supplied format.   Format  must  include  2  string
       specs,  like  so  :  "%s  -  %s"  where  first one will be substituted to short method name, and second -
       description

3rd Berkeley Distribution                      AfterStep v.2.2.12                                    blender(3x)

       name   - string, identifying scanline merging function.

blender - functionality for blending of image data using diofferent algorithms libAfterImage/blender.h

       -   combines   top   and   bottom   RGB   components   based   on   alpha   channel   value:   bottom   =
       bottom*(255-top_alpha)+top*top_alpha; allanon_scanlines() - averages each pixel  between  two  scanlines.
       This  method has been first implemented by Ethan Fisher aka allanon as mode 130: bottom = (bottom+top)/2;
       tint_scanlines() - tints bottom scanline with top scanline( with saturation to prevent overflow) : bottom
       = (bottom*(top/2))/32768; add_scanlines() - adds top scanline  to  bottom  scanline  with  saturation  to
       prevent  overflow:  bottom  =  bottom+top; sub_scanlines() - substrates top scanline from bottom scanline
       with saturation to prevent overflow: bottom = bottom-top; diff_scanlines() - for  each  pixel  calculates
       absolute  difference  between  bottom  and top color value : bottom = (bottom>top)?bottom-top:top-bottom;
       darken_scanlines() - substitutes each pixel with minimum color  value  of  top  and  bottom  :  bottom  =
       (bottom>top)?top:bottom; lighten_scanlines() - substitutes each pixel with maximum color value of top and
       bottom  :  bottom = (bottom>top)?bottom:top; screen_scanlines() - some weird merging algorithm taken from
       GIMP; overlay_scanlines() - some weird merging algorithm taken from GIMP;  hue_scanlines()  -  substitute
       hue  of  bottom scanline with hue of top scanline; saturate_scanlines() - substitute saturation of bottom
       scanline with the saturation of top scanline; value_scanlines() - substitute  value  of  bottom  scanline
       with  the value of top scanline; colorize_scanlines() - combine luminance of bottom scanline with hue and
       saturation of top scanline; dissipate_scanlines()- randomly alpha-blend bottom and top  scanlines,  using
       alpha value of top scanline as a threshold for random values.

       list_scanline_merging()

       hls2rgb()

       rgb2hls()

       rgb2saturation()

       rgb2hue()

       rgb2luminance()

       returns pointer to the scanline merging function on succes.  NULL on failure.

       Functions :
          Colorspace conversion :
                rgb2value(), rgb2saturation(), rgb2hue(), rgb2luminance(),
                rgb2hsv(), rgb2hls(), hsv2rgb(), hls2rgb().

          merge_scanline methods :
                alphablend_scanlines(), allanon_scanlines(),
                tint_scanlines(), add_scanlines(), sub_scanlines(),
                diff_scanlines(), darken_scanlines(), lighten_scanlines(),
                screen_scanlines(), overlay_scanlines(), hue_scanlines(),
                saturate_scanlines(), value_scanlines(),
                colorize_scanlines(), dissipate_scanlines().

          useful merging function name to function translator :
                blend_scanlines_name2func()

       Other libAfterImage modules :
                ascmap.h asfont.h asimage.h asvisual.h blender.h export.h
                import.h transform.h ximage.h

       merge_scanlines_func blend_scanlines_name2func( const  char  *name  );  void  list_scanline_merging(FILE*
       stream, const char *format);