diff --git a/app/src/main/cpp/MpPreview.cpp b/app/src/main/cpp/MpPreview.cpp
index 7ea5756..ceb555f 100644
--- a/app/src/main/cpp/MpPreview.cpp
+++ b/app/src/main/cpp/MpPreview.cpp
@@ -669,16 +669,16 @@ Java_com_xypower_mppreview_Camera2RawFragment_makeHdr3(JNIEnv *env, jclass clazz
             int32_t fence = -1;
             result = AHardwareBuffer_lock(hardwareBuffer, AHARDWAREBUFFER_USAGE_CPU_READ_RARELY, fence, NULL, &outVirtualAddress);
             cv::Mat tmp(bmpInfo.height, bmpInfo.width, CV_8UC4, outVirtualAddress);
-            AHardwareBuffer_unlock(hardwareBuffer, &fence);
             tmp.copyTo(images[idx]);
+            AHardwareBuffer_unlock(hardwareBuffer, &fence);
         }
         else
         {
             void* outAddress = NULL;
             result = AndroidBitmap_lockPixels(env, bitmaps[idx], &outAddress);
             cv::Mat tmp(bmpInfo.height, bmpInfo.width, CV_8UC4, outAddress);
-            AndroidBitmap_unlockPixels(env, bitmaps[idx]);
             tmp.copyTo(images[idx]);
+            AndroidBitmap_unlockPixels(env, bitmaps[idx]);
         }
 
         //convert RGB to BGR