libpng 1.4+ compatibility
--- wv/magick/png.c.orig	2000-12-08 00:35:29.000000000 -0600
+++ wv/magick/png.c	2011-11-20 18:01:26.000000000 -0600
@@ -2015,10 +2015,10 @@
         /*
           Image has a transparent background.
         */
-        transparent_color.red=ping_info->trans_values.red;
-        transparent_color.green=ping_info->trans_values.green;
-        transparent_color.blue=ping_info->trans_values.blue;
-        transparent_color.index=ping_info->trans_values.gray;
+        transparent_color.red=ping_info->trans_color.red;
+        transparent_color.green=ping_info->trans_color.green;
+        transparent_color.blue=ping_info->trans_color.blue;
+        transparent_color.index=ping_info->trans_color.gray;
         if (ping_info->color_type == PNG_COLOR_TYPE_GRAY)
           {
             transparent_color.red=transparent_color.index;
@@ -2029,9 +2029,9 @@
           {
             printf("transparent color = %5d %5d %5d (tRNS = %5d %5d %5d %5d)\n",
                 transparent_color.red,transparent_color.green,
-                transparent_color.blue,ping_info->trans_values.red,
-                ping_info->trans_values.green,ping_info->trans_values.blue,
-                ping_info->trans_values.index);
+                transparent_color.blue,ping_info->trans_color.red,
+                ping_info->trans_color.green,ping_info->trans_color.blue,
+                ping_info->trans_color.index);
             if (ping_info->color_type == PNG_COLOR_TYPE_GRAY)
               printf("transparent color index= %5d\n",transparent_color.index);
           }
@@ -2391,7 +2391,7 @@
                 if (ping_info->color_type == PNG_COLOR_TYPE_PALETTE)
                   {
                     if (index < ping_info->num_trans)
-                      q->index=(unsigned short)UpScale(ping_info->trans[index]);
+                      q->index=(unsigned short)UpScale(ping_info->trans_alpha[index]);
                   }
                 else
                   {
@@ -3646,11 +3646,11 @@
         if (p->index != Opaque)
           {
             ping_info->valid|=PNG_INFO_tRNS;
-            ping_info->trans_values.red=p->red;
-            ping_info->trans_values.green=p->green;
-            ping_info->trans_values.blue=p->blue;
-            ping_info->trans_values.gray=(unsigned short) Intensity(*p);
-            ping_info->trans_values.index=(unsigned short) DownScale(p->index);
+            ping_info->trans_color.red=p->red;
+            ping_info->trans_color.green=p->green;
+            ping_info->trans_color.blue=p->blue;
+            ping_info->trans_color.gray=(unsigned short) Intensity(*p);
+            ping_info->trans_color.index=(unsigned short) DownScale(p->index);
           }
         else
           { 
@@ -3673,7 +3673,7 @@
             {
               if (p->index != Opaque)
                 {
-                  if (!ColorMatch(ping_info->trans_values,*p,0))
+                  if (!ColorMatch(ping_info->trans_color,*p,0))
                     {
                       ping_info->valid&=(~PNG_INFO_tRNS);
                       if (image_info->verbose)
@@ -3689,7 +3689,7 @@
                 }
                else
                 {
-                  if (ColorMatch(ping_info->trans_values,*p,0))
+                  if (ColorMatch(ping_info->trans_color,*p,0))
                     {
                       /* Can't use RGB + tRNS */
                       ping_info->valid&=(~PNG_INFO_tRNS);
@@ -3708,11 +3708,11 @@
             if (save_image_depth == 16 && image->depth == 8)
               {
                 if(image_info->verbose)
-                  printf("reducing trans_values to 8-bit\n");
-                ping_info->trans_values.red&=0xff;
-                ping_info->trans_values.green&=0xff;
-                ping_info->trans_values.blue&=0xff;
-                ping_info->trans_values.gray&=0xff;
+                  printf("reducing trans_color to 8-bit\n");
+                ping_info->trans_color.red&=0xff;
+                ping_info->trans_color.green&=0xff;
+                ping_info->trans_color.blue&=0xff;
+                ping_info->trans_color.gray&=0xff;
               }
           }
       }
@@ -3763,28 +3763,28 @@
               if (save_image_depth == 16 && image->depth == 8)
                 {
                   if(image_info->verbose)
-                    printf("re-expanding trans_values to 16-bit\n");
-                  ping_info->trans_values.red*=0x0101;
-                  ping_info->trans_values.green*=0x0101;
-                  ping_info->trans_values.blue*=0x0101;
-                  ping_info->trans_values.gray*=0x0101;
+                    printf("re-expanding trans_color to 16-bit\n");
+                  ping_info->trans_color.red*=0x0101;
+                  ping_info->trans_color.green*=0x0101;
+                  ping_info->trans_color.blue*=0x0101;
+                  ping_info->trans_color.gray*=0x0101;
                 }
               /*
                 Identify which colormap entry is transparent.
               */
               if (image_info->verbose)
                 printf("Allocating memory for trans\n");
-              ping_info->trans=(unsigned char *)
+              ping_info->trans_alpha=(unsigned char *)
                 AllocateMemory(image->colors*sizeof(unsigned char));
-              if (ping_info->trans == (unsigned char *) NULL)
+              if (ping_info->trans_alpha == (unsigned char *) NULL)
                 WriterExit(ResourceLimitWarning,"Memory allocation failed",
                   image);
               for (i=0; i < (int) image->colors; i++)
               {
-                ping_info->trans[i]=DownScale(Opaque);
-                if (ColorMatch(ping_info->trans_values,image->colormap[i],0))
+                ping_info->trans_alpha[i]=DownScale(Opaque);
+                if (ColorMatch(ping_info->trans_color,image->colormap[i],0))
                   {
-                    ping_info->trans[i]=ping_info->trans_values.index;
+                    ping_info->trans_alpha[i]=ping_info->trans_color.index;
                     break;
                   }
               }