gpujpegtool: avoid some error on unknown extension

if user specifies all image properties, like in the following:

    gpujpegtool -s 1920x1080 -c rgb -f 4444-u8-p0123 \
     -O enc_opt_channel_remap=2103 -e in.gbra out.jpg

do not query the format from the file which avoids the error:

    [GPUJPEG] [Error] GPUJPEG_IMAGE_FILE_UNKNOWN should not be passed!

because of the file extension .gbra, which is now semantically perfectly
correct.

Author: MartinPulec

src/main.c

@@ -251,7 +251,10 @@ adjust_params(struct gpujpeg_parameters* param, struct gpujpeg_image_parameters*
     // if possible, read properties from file
     struct gpujpeg_image_parameters file_param_image = gpujpeg_default_image_parameters();
     const char *raw_file = encode ? in : out;
-    gpujpeg_image_get_properties(raw_file, &file_param_image, encode);
+    if ( param_image->width == 0 || param_image->height == 0 || param_image->pixel_format == GPUJPEG_PIXFMT_NONE ||
+         param_image->color_space == GPUJPEG_NONE ) {
+        gpujpeg_image_get_properties(raw_file, &file_param_image, encode);
+    }
     param_image->width = USE_IF_NOT_NULL_ELSE(param_image->width, file_param_image.width);
     param_image->height = USE_IF_NOT_NULL_ELSE(param_image->height, file_param_image.height);
     if ( param_image->color_space == GPUJPEG_NONE ) {