e predicted values.  The index of the filter
 producing the smallest result is returned.

 <p> As an example, to perform only 'sub' filtering, this method
 could be implemented (non-optimally) as follows:

 <pre>
 for (int i = bytesPerPixel; i < bytesPerRow + bytesPerPixel; i++) {
     int curr = currRow[i] & 0xff;
     int left = currRow[i - bytesPerPixel] & 0xff;
     scratchRow[PNG_FILTER_SUB][i] = (byte)(curr - left);
 }
 return PNG_FILTER_SUB;
 </pre></div>
<dl>
<dt><span class="paramLabel">Parameters: