Overwriting original file, if no output file were specified; closing files than they are no longer needed.

main.c

@@ -78,13 +78,18 @@ int main(int argc, char *argv[]) {
     }
 
     struct image_data * original_image = decompress_image(infile);
+    fclose(infile);
 
     if (original_image == NULL) {
         fprintf(stderr, "Failed to decompress image %s\n", input_filename);
         exit(1);
     }
 
+//    If no output file were specified, use original image
     FILE *outfile;
+    if (out_filename == NULL) {
+        out_filename = input_filename;
+    }
 
     if ((outfile = fopen(out_filename, "wb")) == NULL) {
         fprintf(stderr, "Can not open %s\n", out_filename);
@@ -128,6 +133,8 @@ int main(int argc, char *argv[]) {
     int8_t compress_result;
     compress_result = compress_image(blurred_image, outfile, 90);
 
+    fclose(outfile);
+
     if (compress_result != 0) {
         fprintf(stderr, "Failed to write blurred image to file!\n");