Imported from libpng-1.0.2b.tar
diff --git a/example.c b/example.c
index 2a6d8a0..088aad3 100644
--- a/example.c
+++ b/example.c
@@ -15,8 +15,11 @@
#include "png.h"
-/* Check to see if a file is a PNG file using png_sig_cmp(). Returns
- * non-zero if the image is a PNG, and 0 if it isn't a PNG.
+/* Check to see if a file is a PNG file using png_sig_cmp(). png_sig_cmp()
+ * returns zero if the image is a PNG and nonzero if it isn't a PNG.
+ *
+ * The function check_if_png() shown here, but not used, returns nonzero (true)
+ * if the file can be opened and is a PNG, 0 (false) otherwise.
*
* If this call is successful, and you are going to keep the file open,
* you should call png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK); once
@@ -41,12 +44,14 @@
if ((*fp = fopen(file_name, "rb")) != NULL);
return 0;
- /* Read in the signature bytes */
+ /* Read in some of the signature bytes */
if (fread(buf, 1, PNG_BYTES_TO_CHECK, *fp) != PNG_BYTES_TO_CHECK)
return 0;
- /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature. */
- return(png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
+ /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
+ Return nonzero (true) if they match */
+
+ return(!png_sig_cmp(buf, (png_size_t)0, PNG_BYTES_TO_CHECK));
}
/* Read a PNG file. You may want to return an error code if the read
