opensolaris man page for mlib_imagesubsampleaverage

mlib_ImageSubsampleAverage(3MLIB)			    mediaLib Library Functions				 mlib_ImageSubsampleAverage(3MLIB)

NAME
       mlib_ImageSubsampleAverage, mlib_ImageSubsampleAverage_Fp - subsamples an image with a box filter

SYNOPSIS
       cc [ flag... ] file... -lmlib [ library... ]
       #include <mlib.h>

       mlib_status mlib_ImageSubsampleAverage(mlib_image *dst,
	    const mlib_image *src, mlib_d64 xscale, mlib_d64 yscale);

       mlib_status mlib_ImageSubsampleAverage_Fp(mlib_image *dst,
	    const mlib_image *src, mlib_d64 xscale, mlib_d64 yscale);

DESCRIPTION
       Each function scales an image down with an adaptive box filter.

       The subsampling algorithm performs the scaling operation by averaging all the pixel values from a block in the source image that correspond
       to the destination pixel.

       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 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 over-
       run 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.

       src	 Pointer to source image.

       xscale	 X scale factor. 0.0 < xscale <= 1.0.

       yscale	 Y scale factor. 0.0 < yscale <= 1.0.

RETURN VALUES
       The function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       mlib_ImageSubsampleBinaryToGray(3MLIB),	   mlib_ImageFilteredSubsample(3MLIB),	   mlib_ImageZoomTranslate(3MLIB),    mlib_ImageZoomTrans-
       late_Fp(3MLIB), attributes(5)

SunOS 5.11							    2 Mar 2007					 mlib_ImageSubsampleAverage(3MLIB)