fix buffer overflow for trim() with image wider than high

Dumb error.

Fixes #534

t/300-transform/210-trim.t

@@ -5,38 +5,54 @@ use Test::More;
 use Imager::Test qw(is_image);
 
 {
-  my $im = Imager->new(channels => 4, xsize => 20, ysize => 20);
-  $im->box(filled => 1, xmin => 1, ymin => 2, xmax => 16, ymax => 15, color => "#FFF") or die;
-  my @rect = $im->trim_rect();
-  #$im->write(file => "trim1.png") or die;
-  note "@rect";
-  is_deeply(\@rect, [ 1, 2, 3, 4 ], "check alpha trim");
+  my $im8 = Imager->new(channels => 4, xsize => 200, ysize => 400);
+  $im8->box(filled => 1, xmin => 11, ymin => 23, xmax => 161, ymax => 257, color => "#FFF") or die;
+  my $im16 = $im8->to_rgb16;
+  for my $test ( [ $im8, 8 ], [ $im16, 16 ]) {
+    my ($im, $bits) = @$test;
+
+    {
+      my @rect = $im->trim_rect();
+      note "@rect";
+      is_deeply(\@rect, [ 11, 23, 38, 142 ], "check alpha trim ($bits)");
+    }
+
+    my $imr = $im->rotate(right => 90)
+      or die;
+    is($imr->bits, $bits, "rotated has expected bits ($bits)");
+
+    {
+      my @rect = $imr->trim_rect();
+      note "@rect";
+      is_deeply(\@rect, [ 142, 11, 23, 38 ], "check alpha trim ($bits)");
+    }
+  }
 }
 
 {
-  my $im = Imager->new(channels => 3, xsize => 20, ysize => 20);
+  my $im = Imager->new(channels => 3, xsize => 200, ysize => 300);
   $im->box(filled => 1, color => "#F00");
   $im->box(filled => 1, color => "#00F",
-           xmin => 1, ymin => 2, xmax => 16, ymax => 15);
+           xmin => 31, ymin => 42, xmax => 116, ymax => 251);
   #$im->write(file => "trim2.png") or die;
   {
     my @rect = $im->trim_rect(colors => [ "#F00" ]);
     note "@rect";
-    is_deeply(\@rect, [ 1, 2, 3, 4 ], "check simple color trim");
+    is_deeply(\@rect, [ 31, 42, 83, 48 ], "check simple color trim");
     my $trimmed = $im->trim(colors => [  "#F00" ]);
     ok($trimmed, "got a simple color trimmed image");
-    is_image($trimmed, $im->crop(left => 1, top => 2, right => 17, bottom => 16),
+    is_image($trimmed, $im->crop(left => 31, top => 42, right => 117, bottom => 252),
              "check trimmed image is as expected");
   }
   {
     # intrude into the border a little
     $im->box(filled => 1, color => "#000", xmin => 16, xmax => 18, ymin => 8, ymax => 10);
     my @rect = $im->trim_rect(colors => [ "#F00" ]);
-    is_deeply(\@rect, [ 1, 2, 1, 4 ],
+    is_deeply(\@rect, [ 16, 8, 83, 48 ],
               "check simple color trim with intrusion");
     my $trimmed = $im->trim(colors => [  "#F00" ]);
     ok($trimmed, "got a simple color trimmed image");
-    is_image($trimmed, $im->crop(left => 1, top => 2, right => 19, bottom => 16),
+    is_image($trimmed, $im->crop(left => 16, top => 8, right => 117, bottom => 252),
              "check simple with intrusion trimmed image is as expected");
   }
 }

trim.im

@@ -63,7 +63,7 @@ trim_rect_simple(i_img *im, double transp_threshold, int color_count,
   const int chan_count = check_alpha ? 4 : 3;
   i_img_dim x, y;
 #code im->bits <= 8
-  IM_SAMPLE_T *samps = mymalloc(sizeof(IM_SAMPLE_T) * im->ysize * chan_count);
+  IM_SAMPLE_T *samps = mymalloc(sizeof(IM_SAMPLE_T) * im->xsize * chan_count);
 #if IM_EIGHT_BIT
   const IM_WORK_T work_threshold = floor(IM_SAMPLE_MAX * transp_threshold);
 #else