# HG changeset patch
# User Carnë Draug <carandraug@octave.org>
# Date 1393963800 0
# Node ID e0cc67d5a462ef71b1a73358b5bdbd449e436a56
# Parent  0bfbfb05b1585d64ac23615758918b27e85343a3
Fix writing of grayscale images when there is an alpha channel.

* __magick_read__.cc (encode_uint_image): create Magick::Color object for gray
color with Alpha channel correctly, i.e., repeat the gray value 3 times as if
it was an RGB image.
* imwrite.m: add 4 new tests for writing of single page and multipage, grayscale
and RGB images with alpha channel.

diff -r 0bfbfb05b158 -r e0cc67d5a462 libinterp/dldfcn/__magick_read__.cc
--- a/libinterp/dldfcn/__magick_read__.cc	Tue Mar 04 19:44:19 2014 +0000
+++ b/libinterp/dldfcn/__magick_read__.cc	Tue Mar 04 20:10:00 2014 +0000
@@ -1110,9 +1110,9 @@
               {
                 for (octave_idx_type row = 0; row < nRows; row++)
                   {
-                    Magick::Color c;
-                    c.redQuantum   (double (*img_fvec) / divisor);
-                    c.alphaQuantum (MaxRGB - (double (*a_fvec) / divisor));
+                    double grey = double (*img_fvec) / divisor;
+                    Magick::Color c (grey, grey, grey,
+                                     MaxRGB - (double (*a_fvec) / divisor));
                     pix[GM_idx] = c;
                     img_fvec++;
                     a_fvec++;
diff -r 0bfbfb05b158 -r e0cc67d5a462 scripts/image/imwrite.m
--- a/scripts/image/imwrite.m	Tue Mar 04 19:44:19 2014 +0000
+++ b/scripts/image/imwrite.m	Tue Mar 04 20:10:00 2014 +0000
@@ -137,15 +137,31 @@
 
 ## typical usage with grayscale uint8 images
 %!testif HAVE_MAGICK
-%! bw  = randi (255, 10, 10, 1, "uint8");
-%! r  = write_and_read (bw);
-%! assert (r, bw)
+%! gray  = randi (255, 10, 10, 1, "uint8");
+%! r  = write_and_read (gray);
+%! assert (r, gray)
+
+## grayscale uint8 images with alpha channel
+%!testif HAVE_MAGICK
+%! gray  = randi (255, 10, 10, 1, "uint8");
+%! alpha = randi (255, 10, 10, 1, "uint8");
+%! [r, ~, a] = write_and_read (gray, "Alpha", alpha);
+%! assert (r, gray)
+%! assert (a, alpha)
 
 ## multipage grayscale uint8 images
 %!testif HAVE_MAGICK
-%! bw  = randi (255, 10, 10, 1, 5, "uint8");
-%! r  = write_and_read (bw);
-%! assert (r, bw)
+%! gray  = randi (255, 10, 10, 1, 5, "uint8");
+%! r     = write_and_read (gray);
+%! assert (r, gray)
+
+## multipage RGB uint8 images with alpha channel
+%!testif HAVE_MAGICK
+%! gray  = randi (255, 10, 10, 3, 5, "uint8");
+%! alpha = randi (255, 10, 10, 1, 5, "uint8");
+%! [r, ~, a] = write_and_read (gray, "Alpha", alpha);
+%! assert (r, gray)
+%! assert (a, alpha)
 
 ## typical usage with RGB uint8 images
 %!testif HAVE_MAGICK
@@ -153,9 +169,25 @@
 %! r = write_and_read (rgb);
 %! assert (r, rgb)
 
+## RGB uint8 images with alpha channel
+%!testif HAVE_MAGICK
+%! rgb   = randi (255, 10, 10, 3, "uint8");
+%! alpha = randi (255, 10, 10, 1, "uint8");
+%! [r, ~, a] = write_and_read (rgb, "Alpha", alpha);
+%! assert (r, rgb)
+%! assert (a, alpha)
+
 ## multipage RGB uint8 images
 %!testif HAVE_MAGICK
 %! rgb = randi (255, 10, 10, 3, 5, "uint8");
 %! r = write_and_read (rgb);
 %! assert (r, rgb)
 
+## multipage RGB uint8 images with alpha channel
+%!testif HAVE_MAGICK
+%! rgb   = randi (255, 10, 10, 3, 5, "uint8");
+%! alpha = randi (255, 10, 10, 1, 5, "uint8");
+%! [r, ~, a] = write_and_read (rgb, "Alpha", alpha);
+%! assert (r, rgb)
+%! assert (a, alpha)
+