OpenCV nMatToBitmap Assertion Failed

Issue

I'm getting the following errors using some generic functions within OpenCV for Android

12-05 21:08:55.486: E/cv::error()(6658): OpenCV Error: Assertion failed (src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols) in void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean), file /home/oleg/sources/opencv/modules/java/generator/src/cpp/utils.cpp, line 107
12-05 21:08:55.486: E/org.opencv.android.Utils(6658): nMatToBitmap catched cv::Exception: /home/oleg/sources/opencv/modules/java/generator/src/cpp/utils.cpp:107: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)
12-05 21:08:55.486: E/CameraBridge(6658): Mat type: Mat [ 144*192*CV_8UC3, isCont=true, isSubmat=false, nativeObj=0x1024c0, dataAddr=0x44783010 ]
12-05 21:08:55.486: E/CameraBridge(6658): Bitmap type: 384*288
12-05 21:08:55.486: E/CameraBridge(6658): Utils.matToBitmap() throws an exception: /home/oleg/sources/opencv/modules/java/generator/src/cpp/utils.cpp:107: error: (-215) src.dims == 2 && info.height == (uint32_t)src.rows && info.width == (uint32_t)src.cols in function void Java_org_opencv_android_Utils_nMatToBitmap2(JNIEnv*, jclass, jlong, jobject, jboolean)

I'm not sure if this is the error itself or if it's caused by another problem.

Solution

The assertion error is telling you that one or more of the following tests is failing:

src.dims == 2
info.height == (uint32_t)src.rows
info.width == (uint32_t)src.cols

I'm guessing info contains the dimensions of the destination bitmap. In that case, either your source Mat is not 2 dimensions or the dimensions of the destination bitmap don't match the dimensions of the source Mat.

These two lines

12-05 21:08:55.486: E/CameraBridge(6658): Mat type: Mat [ 144*192*CV_8UC3, isCont=true, isSubmat=false, nativeObj=0x1024c0, dataAddr=0x44783010 ]
12-05 21:08:55.486: E/CameraBridge(6658): Bitmap type: 384*288

suggest that your Mat is 144x192 and your bitmap is 384x288. It looks like one is portrait and the other landscape plus your bitmap is twice the resolution of your Mat.

Answered By - SSteve