[OctDev] Off-by-one error in bmpwrite.m?

[Per P. <per...@ma...>]

Hi,
in preparing a new image.m for Mac OS X (based on code from J. Koski) 
that uses bmpwrite(), and I think I've found a bug in bmpwrite.m.

The color for {R,G,B}={1, 1, 1} is random on OS X and I think the 
problem is that the index into colormap in a .bmp file is zero-based 
(couldn't find a definitive authority). The help for bmpwrite doesn't 
state that a zero-based index is used, so I assume that the patch below 
is the right fix.

/Per

Index: main/image/bmpwrite.m
===================================================================
RCS file: /cvsroot/octave/octave-forge/main/image/bmpwrite.m,v
retrieving revision 1.2
diff -u -d -b -w -r1.2 bmpwrite.m
--- main/image/bmpwrite.m       27 Nov 2002 08:40:10 -0000      1.2
+++ main/image/bmpwrite.m       5 Jul 2004 10:16:01 -0000
@@ -37,7 +37,7 @@

      ## raster image, each line on a 32-bit boundary, padded with zeros
      ## lines written bottom to top.
-    
fwrite(file,postpad(flipud(x)',ceil(columns(x)/4)*4),"uchar",0,arch);
+    
fwrite(file,postpad(flipud(x-1)',ceil(columns(x)/4)*4),"uchar",0,arch);
      fclose(file);
  endfunction