blender(1)               AfterStep X11 window manager               blender(1)



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

NAMEblender
DESCRIPTION
       Defines implemented methods for ASScanline combining, that could be
       passed to merge_layers() via ASImageLayer structure.  Also includes
       functions for colorspace conversion RGB<->HSV and RGB<->HLS.

SEE ALSO
       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

AUTHOR
       Sasha Vasko <sasha at aftercode dot net>

NAMEcolorspace
DESCRIPTION
       RGB colorspace: each color is represented as a combination of red,
       green and blue values. Each value can be in 2 formats : 8 bit and 24.8
       bit. 24.8 bit makes for 32bit value with lower 8 bits used as a
       fraction for better calculation precision.

       HSV colorspace: each color is represented as a combination of hue,
       saturation and value. Hue is generally colorizing component where value
       represents brightness.

       HLS colorspace: each color is represented as a combination of hue,
       luminance and saturation. It is analogous to HSV with value substituted
       by luminance, except that luminance could be both negative and
       positive.

       alpha channel could be added to any of the above colorspaces. alpha
       channel is generally used to define transparentness of the color.
       libAfterImage is using ARGB colorspace as a base colorspace, and
       represents most colors as ARGB32 values or ASScanline scanlines of
       pixels.

NAMErgb2value()
       rgb2saturation()

       rgb2hue()

       rgb2luminance()



SYNOPSIS
       CARD32 rgb2value( CARD32 red, CARD32 green, CARD32 blue ); CARD32
       rgb2saturation( CARD32 red, CARD32 green, CARD32 blue ); CARD32
       rgb2hue( CARD32 red, CARD32 green, CARD32 blue ); CARD32 rgb2luminance
       (CARD32 red, CARD32 green, CARD32 blue );

INPUTS
       red    - 32 bit value, 16 lower bits of which represent red channel

       green  - 32 bit value, 16 lower bits of which represent green channel

       blue   - 32 bit value, 16 lower bits of which represent blue channel


RETURN VALUE
       32 bit value, 16 lower bits of which represent value, saturation, hue,
       or luminance respectively.

DESCRIPTION
       This functions translate RGB color into respective coordinates of HSV
       and HLS colorspaces.  Returned hue values are in 16bit format. To
       translate it to and from conventional 0-360 degree range, please use :
       degrees2hue16() - converts conventional hue in 0-360 range into hue16
       hue162degree()  - converts 16bit hue value into conventional degrees.

NAMErgb2hsv()
       rgb2hls()



SYNOPSIS
       CARD32 rgb2hsv( CARD32 red, CARD32 green, CARD32 blue,
                       CARD32 *saturation, CARD32 *value ); CARD32 rgb2hls(
       CARD32 red, CARD32 green, CARD32 blue,
                       CARD32 *luminance, CARD32 *saturation );

INPUTS
       red    - 32 bit value, 16 lower bits of which represent red channel

       green  - 32 bit value, 16 lower bits of which represent green channel

       blue   - 32 bit value, 16 lower bits of which represent blue channel


RETURN VALUE
       32 bit value, 16 lower bits of which represent hue.  32bit value
       pointed to by luminance, value and saturation will be set respectively
       to color luminance, value and saturation.

DESCRIPTION
       This functions translate RGB color into full set of HSV and HLS
       coordinates at once. These functions work faster then separate
       translation into each channel.

NAMEhsv2rgb()
       hls2rgb()



SYNOPSIS
       void hsv2rgb( CARD32 hue, CARD32 saturation, CARD32 value,
                     CARD32 *red, CARD32 *green, CARD32 *blue); void hls2rgb(
       CARD32 hue, CARD32 luminance, CARD32 saturation,
                     CARD32 *red, CARD32 *green, CARD32 *blue);

INPUTS
       hue    - 32 bit value, 16 lower bits of which represent hue.

       saturation
              - 32 bit value, 16 lower bits of which represent saturation.

       value  - 32 bit value, 16 lower bits of which represent value.

       luminance
              - 32 bit value, 16 lower bits of which represent luminance.


RETURN VALUE
       32bit value pointed to by red, green and blue will be set respectively
       to RGB color channels.

DESCRIPTION
       This functions performs reverse translation from HSV and HSL to RGB
       color

NAMEalphablend_scanlines()
       - 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.


SYNOPSIS
       void alphablend_scanlines( ASScanline *bottom, ASScanline *top, int );
       void allanon_scanlines   ( ASScanline *bottom, ASScanline *top, int );
       void tint_scanlines      ( ASScanline *bottom, ASScanline *top, int );
       void add_scanlines       ( ASScanline *bottom, ASScanline *top, int );
       void sub_scanlines       ( ASScanline *bottom, ASScanline *top, int );
       void diff_scanlines      ( ASScanline *bottom, ASScanline *top, int );
       void darken_scanlines    ( ASScanline *bottom, ASScanline *top, int );
       void lighten_scanlines   ( ASScanline *bottom, ASScanline *top, int );
       void screen_scanlines    ( ASScanline *bottom, ASScanline *top, int );
       void overlay_scanlines   ( ASScanline *bottom, ASScanline *top, int );
       void hue_scanlines       ( ASScanline *bottom, ASScanline *top, int );
       void saturate_scanlines  ( ASScanline *bottom, ASScanline *top, int );
       void value_scanlines     ( ASScanline *bottom, ASScanline *top, int );
       void colorize_scanlines  ( ASScanline *bottom, ASScanline *top, int );
       void dissipate_scanlines ( ASScanline *bottom, ASScanline *top, int );

INPUTS
       bottom - pointer to the ASScanline that will be overalayed

       top    - pointer to ASScanline that will overlay bottom.


DESCRIPTION
       This functions accept 2 scanlines as an arguments stored in ASScanline
       structures with data in 24.8 format. Merging operation is performed on
       these scanlines and result is stored in bottom ASScanline.  The
       following are merging methods used in each function :

NAMEblend_scanlines_name2func()
       list_scanline_merging()



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

INPUTS
       name   - string, identifying scanline merging function.


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

DESCRIPTION
       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(1)
