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ASImage Blendingfunctionality for blending of image data using diofferent algorithms



    libAfterImage/blender.h
  • NAME
    blender

  • 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().
    
       usefull 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>
    
    libAfterImage/colorspace
  • NAME
    colorspace

  • 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.
    
    libAfterImage/rgb2value()
  • NAME
    rgb2value()

    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.
    
    libAfterImage/rgb2hsv()
  • NAME
    rgb2hsv()

    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.
    
    libAfterImage/hsv2rgb()
  • NAME
    hsv2rgb()

    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 
    
    libAfterImage/merge_scanline
  • NAME
    alphablend_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 wierd merging algorithm taken from GIMP;

    overlay_scanlines()

    - some wierd 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 :
    
    
    libAfterImage/blend_scanlines_name2func()
  • NAME
    blend_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
    


AfterStep Documentation   -   October 2005     ( 80% complete )

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