From fcf06169b67cb58a2ab649c11889f91cb400dfd8 Mon Sep 17 00:00:00 2001
From: glennrp <glennrp@git.imagemagick.org>
Date: Mon, 5 Nov 2012 14:57:08 +0000
Subject: [PATCH] Let libpng expand sub-8-bit pixels.

---
 coders/png.c | 84 ++++++++++------------------------------------------
 1 file changed, 15 insertions(+), 69 deletions(-)

diff --git a/coders/png.c b/coders/png.c
index 86dac72c9..f0ee8457f 100644
--- a/coders/png.c
+++ b/coders/png.c
@@ -2025,6 +2025,7 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
     pass,
     ping_bit_depth,
     ping_color_type,
+    ping_file_depth,
     ping_interlace_method,
     ping_compression_method,
     ping_filter_method,
@@ -2309,6 +2310,8 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
                &ping_interlace_method,&ping_compression_method,
                &ping_filter_method);
 
+  ping_file_depth = ping_bit_depth;
+
   (void) png_get_tRNS(ping, ping_info, &ping_trans_alpha, &ping_num_trans,
                       &ping_trans_color);
 
@@ -2316,11 +2319,8 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
 
   if (ping_bit_depth < 8)
     {
-      if (((int) ping_color_type == PNG_COLOR_TYPE_PALETTE))
-        {
-          png_set_packing(ping);
-          ping_bit_depth = 8;
-        }
+       png_set_packing(ping);
+       ping_bit_depth = 8;
     }
 
   image->depth=ping_bit_depth;
@@ -2648,16 +2648,16 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
 
         bkgd_scale = 1;
 
-        if (ping_bit_depth == 1)
+        if (ping_file_depth == 1)
            bkgd_scale = 255;
 
-        else if (ping_bit_depth == 2)
+        else if (ping_file_depth == 2)
            bkgd_scale = 85;
 
-        else if (ping_bit_depth == 4)
+        else if (ping_file_depth == 4)
            bkgd_scale = 17;
 
-        if (ping_bit_depth <= 8)
+        if (ping_file_depth <= 8)
            bkgd_scale *= 257;
 
         ping_background->red *= bkgd_scale;
@@ -2709,7 +2709,7 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
         (void) LogMagickEvent(CoderEvent,GetMagickModule(),
           "    Reading PNG tRNS chunk.");
 
-      max_sample = (int) ((one << ping_bit_depth) - 1);
+      max_sample = (int) ((one << ping_file_depth) - 1);
 
       if ((ping_color_type == PNG_COLOR_TYPE_GRAY &&
           (int)ping_trans_color->gray > max_sample) ||
@@ -2730,7 +2730,7 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
           int
              scale_to_short;
 
-          scale_to_short = 65535L/((1UL << ping_bit_depth)-1);
+          scale_to_short = 65535L/((1UL << ping_file_depth)-1);
 
           /* Scale transparent_color to short */
           transparent_color.red= scale_to_short*ping_trans_color->red;
@@ -2818,7 +2818,7 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
 
       image->storage_class=PseudoClass;
       one=1;
-      image->colors=one << ping_bit_depth;
+      image->colors=one << ping_file_depth;
 #if (MAGICKCORE_QUANTUM_DEPTH == 8)
       if (image->colors > 256)
         image->colors=256;
@@ -2875,7 +2875,7 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
           size_t
             scale;
 
-          scale=(QuantumRange/((1UL << ping_bit_depth)-1));
+          scale=(QuantumRange/((1UL << ping_file_depth)-1));
 
           if (scale < 1)
              scale=1;
@@ -2894,14 +2894,14 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
       char
         msg[MaxTextExtent];
 
-     /* encode ping_width, ping_height, ping_bit_depth, ping_color_type,
+     /* encode ping_width, ping_height, ping_file_depth, ping_color_type,
         ping_interlace_method in value */
 
      (void) FormatLocaleString(msg,MaxTextExtent,
          "%d, %d",(int) ping_width, (int) ping_height);
      (void) SetImageProperty(image,"png:IHDR.width,height    ",msg,exception);
 
-     (void) FormatLocaleString(msg,MaxTextExtent,"%d",(int) ping_bit_depth);
+     (void) FormatLocaleString(msg,MaxTextExtent,"%d",(int) ping_file_depth);
      (void) SetImageProperty(image,"png:IHDR.bit_depth       ",msg,exception);
 
      (void) FormatLocaleString(msg,MaxTextExtent,"%d (%s)",
@@ -3151,60 +3151,6 @@ static Image *ReadOnePNGImage(MngInfo *mng_info,
 
         switch (ping_bit_depth)
         {
-          case 1:
-          {
-            register ssize_t
-              bit;
-
-            for (x=(ssize_t) image->columns-7; x > 0; x-=8)
-            {
-              for (bit=7; bit >= 0; bit--)
-                *r++=(Quantum) ((*p) & (0x01 << bit) ? 0x01 : 0x00);
-              p++;
-            }
-
-            if ((image->columns % 8) != 0)
-              {
-                for (bit=7; bit >= (ssize_t) (8-(image->columns % 8)); bit--)
-                  *r++=(Quantum) ((*p) & (0x01 << bit) ? 0x01 : 0x00);
-              }
-
-            break;
-          }
-
-          case 2:
-          {
-            for (x=(ssize_t) image->columns-3; x > 0; x-=4)
-            {
-              *r++=(*p >> 6) & 0x03;
-              *r++=(*p >> 4) & 0x03;
-              *r++=(*p >> 2) & 0x03;
-              *r++=(*p++) & 0x03;
-            }
-
-            if ((image->columns % 4) != 0)
-              {
-                for (i=3; i >= (ssize_t) (4-(image->columns % 4)); i--)
-                  *r++=(Quantum) ((*p >> (i*2)) & 0x03);
-              }
-
-            break;
-          }
-
-          case 4:
-          {
-            for (x=(ssize_t) image->columns-1; x > 0; x-=2)
-            {
-              *r++=(*p >> 4) & 0x0f;
-              *r++=(*p++) & 0x0f;
-            }
-
-            if ((image->columns % 2) != 0)
-              *r++=(*p++ >> 4) & 0x0f;
-
-            break;
-          }
-
           case 8:
           {
             if (ping_color_type == 4)
-- 
2.40.0