gpujpeg_image_get_properties: fix ret in main

+ updated the function documentation (ret val semantics)

Author: MartinPulec

libgpujpeg/gpujpeg_common.h

@@ -425,15 +425,11 @@ gpujpeg_image_save_to_file(char* filename, const uint8_t* image, size_t image_si
 /**
  * Reads/obtains properties from uncompressed file (PNM etc.)
  *
- * For raw files it obtains only pixel format deduced from file extension.
+ * For files without header (.rgb, .yuv...) it obtains only color space pixel format deduced from file extension.
  *
- * gpujpeg_image_parameters::comp_size is not set by the function and should be deduced from pixel_format
- *
- * May also return some with a null value - eg. when the file doesn't exist
- * but color space may be deduced from extension.
  * @retval 0 on success; != 0 on error
  * @retval -1 on error
- * @retval 1 only pixel format was deduced from file extension
+ * @retval 1 only color space and  pixel format was deduced from file extension (see above)
  */
 GPUJPEG_API int
 gpujpeg_image_get_properties(const char *filename, struct gpujpeg_image_parameters *param_image, int file_exists);

src/main.c

@@ -158,7 +158,7 @@ static int print_image_info(const char *filename, int verbose) {
         return print_image_info_jpeg(filename, verbose);
     }
     struct gpujpeg_image_parameters param_image = { 0 };
-    if (gpujpeg_image_get_properties(filename, &param_image, 1) != 0) {
+    if ( gpujpeg_image_get_properties(filename, &param_image, 1) < 0 ) {
         fprintf(stderr, "Error getting raw image %s info!\n", filename);
         return 1;
     }