mediaLib Library Functions
                           mlibImageSubsampleBinaryToGray(3MLIB)



NAME
     mlibImageSubsampleBinaryToGray - subsamples a binary  image
     and converts it to a grayscale image

SYNOPSIS
     cc [ flag... ] file... -lmlib [ library... ]
     #include 

     mlibstatus mlibImageSubsampleBinaryToGray(mlibimage *dst,
          const mlibimage *src, mlibd64 xscale, mlibd64 yscale,
          const mlibu8 *lutGray);


DESCRIPTION
     The mlibImageSubsampleBinaryToGray() function subsamples  a
     binary  (MLIBIT)  image  and  converts  it  to a grayscale
     (MLIBYTE) image.


     The subsampling algorithm performs the scaling operation  by
     accumulating   all   the  bits  in  the  source  image  that
     correspond to the destination pixel and, based on the x  and
     y  scaling  factors,  reserving  consecutive  indexes in the
     colormap for the maximum number of gray levels  possible  in
     the destination image. The destination image pixel values of
     this  function  are  either  gray  levels  or  indexes   (if
     lutGray==NUL).


     For representing the source block of pixels that is used  to
     determine destination pixel values, the index 0 represents a
     block with no 1's (all 0's), the index 1 represents a  block
     with a single 1, and so on. If the scaling factors require a
     fractional block of source pixels to determine a destination
     pixel value, the block size is rounded up. For example, if a
     2.2-by-2.2 block of  source  pixels  would  be  required  to
     determine  destination pixel values, a 3-by-3 block is used,
     resulting in 10 possible gray levels and therefore 10 color-
     map indexes, whose values are 0 through 9.


     The width and height of the source block for  a  destination
     pixel are computed as:

         blockX = (int)ceil(1.0/xscale);
         blockY = (int)ceil(1.0/yscale);



     If we denote a pixel's location in an image  by  its  column
     number and row number (both counted from 0), the destination



SunOS 5.11           Last change: 2 Mar 2007                    1






mediaLib Library Functions
                           mlibImageSubsampleBinaryToGray(3MLIB)



     pixel at (i, j) is backward mapped to the source block whose
     upper-left  corner  pixel  is  at  (xValues[i], yValues[j]),
     where

         xValues[i] = (int)(i/xscale ] 0.5);
         yValues[j] = (int)(j/yscale ] 0.5);



     The width and height of the filled area in  the  destination
     are restricted by

         dstW = (int)(srcWidth * xscale);
         dstH = (int)(srcHeight * yscale);



     where srcWidth and srcHeight are width  and  height  of  the
     source image.


     Since the block size in source is defined from scale factors
     with  roundup, some blocks (the rightmost and the bottommost
     blocks) may overrun the border of  the  source  image  by  1
     pixel.  In  this  case,  such blocks are moved by 1 pixel to
     left/up direction in order to be inside of the source image.

PARAMETERS
     The function takes the following arguments:

     dst        Pointer to destination image . It must be of type
                MLIBYTE and have just one channel.


     src        Pointer to source  image.  It  must  be  of  type
                MLIBIT and have just one channel.


     xscale     X scale factor. 0.0 < xscale < 1.0.


     yscale     Y scale factor. 0.0 < yscale < 1.0.


     lutGray    Pointer to a grayscale lookup-table.


RETURN VALUES
     The function returns MLIBSUCES if  successful.  Otherwise
     it returns MLIBFAILURE.




SunOS 5.11           Last change: 2 Mar 2007                    2






mediaLib Library Functions
                           mlibImageSubsampleBinaryToGray(3MLIB)



ATRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Interface Stability          Committed                   
    
     MT-Level                     MT-Safe                     
    


SEE ALSO
     mlibImageZoomTranslateToGray(3MLIB),
     mlibImageSubsampleAverage(3MLIB), attributes(5)




































SunOS 5.11           Last change: 2 Mar 2007                    3






mediaLib Library Functions
                           mlibImageSubsampleBinaryToGray(3MLIB)






















































SunOS 5.11           Last change: 2 Mar 2007                    4