added an implementation for image mode 4.

diff --git a/lib/png.c b/lib/png.c
index 8dd105b..d0fb4ef 100644 (file)
--- a/lib/png.c
+++ b/lib/png.c
@@ -107,12 +107,8 @@ int png_read_header(FILE*fi, struct png_header*header)
            f = data[11];     // filter mode (0)
            i = data[12];     // interlace mode (0)
 
-           if(b!=0 && b!=2 && b!=3 && b!=6) {
+           if(b!=0 && b!=4 && b!=2 && b!=3 && b!=6) {
                fprintf(stderr, "Image mode %d not supported!\n", b);
-               if(b == 4) {
-                   fprintf(stderr, "(This is a grayscale image with alpha channel-\n");
-                   fprintf(stderr, " try converting it into an RGB image with alpha channel)\n");
-               }
                return 0;
            }
            if(a!=8 && (b==2 || b==6)) {
@@ -467,6 +463,7 @@ int getPNG(char*sname, int*destwidth, int*destheight, unsigned char**destdata)
     int alphapalettelen = 0;
     struct png_header header;
     int bypp;
+    U8*data2 = 0;
 
     FILE *fi;
     U8 *scanline;
@@ -482,10 +479,9 @@ int getPNG(char*sname, int*destwidth, int*destheight, unsigned char**destdata)
     }
 
     if(header.mode == 3 || header.mode == 0) bypp = 1;
-    else
-    if(header.mode == 2) bypp = 3;
-    else
-    if(header.mode == 6) bypp = 4;
+    else if(header.mode == 4) bypp = 2;
+    else if(header.mode == 2) bypp = 3;
+    else if(header.mode == 6) bypp = 4;
     else {
        printf("ERROR: mode:%d\n", header.mode);
        return 0;
@@ -553,10 +549,49 @@ int getPNG(char*sname, int*destwidth, int*destheight, unsigned char**destdata)
 
     *destwidth = header.width;
     *destheight = header.height;
+       
+    data2 = (U8*)malloc(header.width*header.height*4);
 
-    if(header.mode == 6 || header.mode == 2)
+    if(header.mode == 4)
     {
-       U8*data2 = (U8*)malloc(header.width*header.height*4);
+       int i,s=0;
+       int x,y;
+       int pos=0;
+       U8* old= (U8*)malloc(header.width*2);
+       memset(old, 0, header.width*2);
+       *destdata = data2;
+       for(y=0;y<header.height;y++) {
+           int mode = imagedata[pos++]; //filter mode
+           U8*src;
+           U8*dest;
+           int x;
+           dest = &data2[(y*header.width)*4];
+
+           if(header.bpp == 8) {
+               /* one byte per pixel */
+               src = &imagedata[pos];
+               pos+=header.width*2;
+           } else {
+               /* not implemented yet */
+               fprintf(stderr, "ERROR: mode=4 bpp:%d\n", header.bpp);
+               free(data2);
+               return 0;
+           }
+
+           applyfilter2(mode, src, old, dest, header.width);
+           memcpy(old, dest, header.width*2);
+
+           for(x=header.width-1;x>=0;x--) {
+               U8 gray = dest[x*2+0];
+               U8 alpha = dest[x*2+1];
+               dest[x*4+0] = alpha;
+               dest[x*4+1] = gray;
+               dest[x*4+2] = gray;
+               dest[x*4+3] = gray;
+           }
+       }
+       free(old);
+    } else if(header.mode == 6 || header.mode == 2) {
        int i,s=0;
        int x,y;
        int pos=0;
@@ -575,7 +610,7 @@ int getPNG(char*sname, int*destwidth, int*destheight, unsigned char**destdata)
                pos+=header.width*(header.mode==6?4:3);
            } else {
                /* not implemented yet */
-               printf("ERROR: bpp:%d\n", header.bpp);
+               fprintf(stderr, "ERROR: bpp:%d\n", header.bpp);
                free(data2);
                return 0;
            }
@@ -593,7 +628,6 @@ int getPNG(char*sname, int*destwidth, int*destheight, unsigned char**destdata)
        }
     } else if(header.mode == 0 || header.mode == 3) {
        COL*rgba = 0;
-       U8*data2 = (U8*)malloc(header.width*header.height*4);
        U8*tmpline = (U8*)malloc(header.width+1);
        U8*destline = (U8*)malloc(header.width+1);
        int i,x,y;