GraphicsMagick: coders/bmp.c Populate upper byte to lower byte ...

changeset 73f00b8d83ef in /hg/GraphicsMagick
details: http://hg.GraphicsMagick.org/hg/GraphicsMagick?cmd=changeset;node=73f00b8d83ef
summary: coders/bmp.c  Populate upper byte to lower byte even for lower bpp than 8.

diffstat:

 ChangeLog    |   6 ++++++
 coders/bmp.c |  13 ++++++++-----
 2 files changed, 14 insertions(+), 5 deletions(-)

diffs (65 lines):

diff -r 7af1b1f1d506 -r 73f00b8d83ef ChangeLog
--- a/ChangeLog	Thu Aug 17 02:06:31 2023 +0200
+++ b/ChangeLog	Thu Aug 17 09:57:52 2023 +0200
@@ -1,3 +1,9 @@
+2023-08-16  Fojtik Jaroslav  <[email protected]>
+
+	* coders/bmp.c  Populate upper byte to lower byte even for lower
+	bpp than 8. It overcomes quantum scalling error in gm. Code should
+	be redesigned, but it is better than previous state.
+
 2023-08-17  Fojtik Jaroslav  <[email protected]>
 
 	* coders/bmp.c  Enforce default matte for 40 byte header & 32bpp.
diff -r 7af1b1f1d506 -r 73f00b8d83ef coders/bmp.c
--- a/coders/bmp.c	Thu Aug 17 02:06:31 2023 +0200
+++ b/coders/bmp.c	Thu Aug 17 09:57:52 2023 +0200
@@ -1287,7 +1287,7 @@
                 }
               if ( bmp_info.bits_per_pixel == 32)
                 {
-                  image->matte = 1;
+                  image->matte = True;
                   bmp_info.alpha_mask=0xff000000U;
                   bmp_info.red_mask=0x00ff0000U;
                   bmp_info.green_mask=0x0000ff00U;
@@ -1514,6 +1514,7 @@
           }
         case 32:
           {
+             /* char ZeroOpacity = 1; */
             /*
               Convert bitfield encoded DirectColor scanline.
             */
@@ -1537,18 +1538,19 @@
                     pixel|=((magick_uint32_t) *p++ << 16);
                     pixel|=((magick_uint32_t) *p++ << 24);
                     red=((pixel & bmp_info.red_mask) << shift.red) >> 16;
-                    if (quantum_bits.red == 8)
+                    if (quantum_bits.red <= 8)
                       red|=(red >> 8);
                     green=((pixel & bmp_info.green_mask) << shift.green) >> 16;
-                    if (quantum_bits.green == 8)
+                    if (quantum_bits.green <= 8)
                       green|=(green >> 8);
                     blue=((pixel & bmp_info.blue_mask) << shift.blue) >> 16;
-                    if (quantum_bits.blue == 8)
+                    if (quantum_bits.blue <= 8)
                       blue|=(blue >> 8);
                     if (image->matte != False)
                       {
                         opacity=((pixel & bmp_info.alpha_mask) << shift.opacity) >> 16;
-                        if (quantum_bits.opacity == 8)
+                        /* if(opacity!=0) ZeroOpacity=0; */
+                        if (quantum_bits.opacity <= 8)
                           opacity|=(opacity >> 8);
                         q->opacity=MaxRGB-ScaleShortToQuantum(opacity);
                       }
@@ -1570,6 +1572,7 @@
                         break;
                     }
               }
+            /* if(ZeroOpacity) image->matte = False; */
             break;
           }
         default: