demo: Fix wrong color mapping

https://stackoverflow.com/questions/46634600/pyplot-colormesh-creates-plot-with-wrong-color-mapping

Author: synml

demo.py

@@ -50,6 +50,6 @@
         # 1 배치단위 처리
         assert target.shape[0] == output.shape[0]
         for i in range(target.shape[0]):
-            plt.imsave(os.path.join(result_dir, image_names[step]), output[i].cpu(), cmap=cmap)
-            plt.imsave(os.path.join(groundtruth_dir, image_names[step]), target[i], cmap=cmap)
+            plt.imsave(os.path.join(result_dir, image_names[step]), output[i].cpu(), cmap=cmap, vmin=0, vmax=cmap.N)
+            plt.imsave(os.path.join(groundtruth_dir, image_names[step]), target[i], cmap=cmap, vmin=0, vmax=cmap.N)
             step += 1