print a more detailed error message for mode 4 images.

diff --git a/src/png2swf.c b/src/png2swf.c
index 188bacd..58ebd17 100644 (file)
--- a/src/png2swf.c
+++ b/src/png2swf.c
@@ -168,6 +168,10 @@ int png_read_header(FILE*fi, struct png_header*header)
 
            if(b!=0 && 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");
+               }
                exit(1);
            }
            if(a!=8 && (b==2 || b==6)) {
@@ -556,7 +560,7 @@ TAG *MovieAddFrame(SWF * swf, TAG * t, char *sname, int id)
            }
            if(header.mode==6)
                applyfilter4(mode, src, old, dest, header.width);
-           else
+           else if(header.mode==2)
                applyfilter3(mode, src, old, dest, header.width);
        }
 
@@ -591,8 +595,7 @@ TAG *MovieAddFrame(SWF * swf, TAG * t, char *sname, int id)
            swf_SetLosslessBits(t, header.width, header.height, data2, BMF_32BIT);
        }
        free(data2);
-    }
-    else if(header.mode == 0 || header.mode == 3) {
+    } else if(header.mode == 0 || header.mode == 3) {
        RGBA*rgba;
        int swf_width = BYTES_PER_SCANLINE(header.width);
        U8*data2 = malloc(swf_width*header.height);