Added support for custom data with png image files

src/detector.c

@@ -407,6 +407,7 @@ void validate_detector_recall(char *datacfg, char *cfgfile, char *weightfile)
         find_replace(labelpath, "JPEGImages", "labels", labelpath);
         find_replace(labelpath, ".jpg", ".txt", labelpath);
         find_replace(labelpath, ".JPEG", ".txt", labelpath);
+	find_replace(labelpath, ".png", ".txt", labelpath);
 
         int num_labels = 0;
         box_label *truth = read_boxes(labelpath, &num_labels);