Add comment about exif metadata key 270.

plotid/save_plot.py

@@ -73,6 +73,7 @@ def save_plot(figures, plot_names, figure_ids=[], extension="png"):
         elif all(x in str(type(fig)) for x in ["PIL", "ImageFile"]):
             plot_path.append(plot_names[i] + ".tmp." + extension)
             img_exif = fig.getexif()
+            # 270 or 0x010e is the EXIF identifier for "ImageDescription"
             img_exif[270] = figure_ids[i]
             fig.save(plot_path[i], exif=img_exif)
         else: