error: (-215) func != 0 in function convertTo

asked Aug 28 '13

dagey
16 ●1 ●1 ●4

updated Aug 28 '13

StevenPuttemans

20029 ●16 ●82 ●207 http://stevenputtemans...

Hi,

In the following code I get an opencv assertion and I don't understand why. Any help will be very much appreciated.

The code:

Mat m(pm->get_current_tracked_keypoints()); // after this line: m.type=7 and m.depth=7
Mat m1;
m.convertTo(m1, CV_32F);

The error:

OpenCV Error: Assertion failed (func != 0) in convertTo, file /build/buildd/opencv-2.3.1/modules/core/src/convert.cpp, line 937
terminate called after throwing an instance of 'cv::Exception'
  what():  /build/buildd/opencv-2.3.1/modules/core/src/convert.cpp:937: error: (-215) func != 0 in function convertTo

Thanks

Comments

m.depth=7 means CV_USRTYPE1. It is a generic type contant and OpenCV doesn't know, how to work with it. What exactly does pm->get_current_tracked_keypoints() return?

Vladislav Vinogradov (Aug 28 '13)edit

It returns an std::vector<KeyPoint>. I am trying to get a CV_32F mat that contains this list of points. Thanks

dagey (Aug 28 '13)edit

Then loop over your vector and copy each keypoint to a row in the matrix.

StevenPuttemans (Aug 28 '13)edit

It worked, thank you very much !!

dagey (Aug 29 '13)edit

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answered Aug 28 '13

Moster
1716 ●5 ●24

updated Aug 28 '13

Its simple. The conversion from Mat depth 7 to 5 does not exist in opencv.

BinaryFunc func = noScale ? getConvertFunc(sdepth, ddepth) : getConvertScaleFunc(sdepth, ddepth);

This is the the function func that you see in cv_assert.

BinaryFunc getConvertFunc(int sdepth, int ddepth)
{
     return cvtTab[CV_MAT_DEPTH(ddepth)][CV_MAT_DEPTH(sdepth)];
}

This is the function that determines the function which is used for conversion. It checks the array cvtTab. (ddepth is 5, sdepth is 7)

static BinaryFunc cvtTab[][8] =
{
{
    (BinaryFunc)cvt8u, (BinaryFunc)cvt8s8u, (BinaryFunc)cvt16u8u,
    (BinaryFunc)cvt16s8u, (BinaryFunc)cvt32s8u, (BinaryFunc)cvt32f8u,
    (BinaryFunc)cvt64f8u, 0
},
{
    (BinaryFunc)cvt8u8s, (BinaryFunc)cvt8u, (BinaryFunc)cvt16u8s,
    (BinaryFunc)cvt16s8s, (BinaryFunc)cvt32s8s, (BinaryFunc)cvt32f8s,
    (BinaryFunc)cvt64f8s, 0
},
{
    (BinaryFunc)cvt8u16u, (BinaryFunc)cvt8s16u, (BinaryFunc)cvt16u,
    (BinaryFunc)cvt16s16u, (BinaryFunc)cvt32s16u, (BinaryFunc)cvt32f16u,
    (BinaryFunc)cvt64f16u, 0
},
{
    (BinaryFunc)cvt8u16s, (BinaryFunc)cvt8s16s, (BinaryFunc)cvt16u16s,
    (BinaryFunc)cvt16u, (BinaryFunc)cvt32s16s, (BinaryFunc)cvt32f16s,
    (BinaryFunc)cvt64f16s, 0
},
{
    (BinaryFunc)cvt8u32s, (BinaryFunc)cvt8s32s, (BinaryFunc)cvt16u32s,
    (BinaryFunc)cvt16s32s, (BinaryFunc)cvt32s, (BinaryFunc)cvt32f32s,
    (BinaryFunc)cvt64f32s, 0
},
{
    (BinaryFunc)cvt8u32f, (BinaryFunc)cvt8s32f, (BinaryFunc)cvt16u32f,
    (BinaryFunc)cvt16s32f, (BinaryFunc)cvt32s32f, (BinaryFunc)cvt32s,
    (BinaryFunc)cvt64f32f, 0
},
{
    (BinaryFunc)cvt8u64f, (BinaryFunc)cvt8s64f, (BinaryFunc)cvt16u64f,
    (BinaryFunc)cvt16s64f, (BinaryFunc)cvt32s64f, (BinaryFunc)cvt32f64f,
    (BinaryFunc)cvt64s, 0
},
{
    0, 0, 0, 0, 0, 0, 0, 0
}
};

As you can see cvtTab[5][7] is 0, so cv_assert will fail. Depth 7 is CV_USRTYPE1. I dont exactly know what usrtype1 is, but I guess it means a custom Mat type. So opencv cant handle the conversion since it does not exactly know the type.

Comments

Thank you very much for this detailed response!

I am trying to build a kd-tree with cv::flann::Index. So, I was trying to build it with a set of keypoints that I have by inserting them to a Mat but in order to build it I need a CV_32F mat and I can't get it right. How do you think I can solve this problem ? Thanks

dagey (Aug 28 '13)edit

Do what Steven says. Loop through all KeyPoints and add them manually. Simplest way would be:

int size = keypointVector.size();

Mat keyPoints (size, 2, CV32FC1);

for(int i = 0; i < size; i++) {

keyPoints.at<float>(i,0) = keyPointVector[i].pt.x;

keyPoints.at<float>(i,1) = keyPointVector[i].pt.y;

}

This might be done more elegant or faster: http://docs.opencv.org/doc/tutorials/core/how_to_scan_images/how_to_scan_images.html

Moster (Aug 28 '13)edit

aaaa how I didn't think of it ! It worked, thank you very much !

dagey (Aug 29 '13)edit

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error: (-215) func != 0 in function convertTo

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