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Why am I getting assertion failed in cvtColor even when convertTo was called in the line before?

asked 2013-01-18 23:45:14 -0500

ZachTM gravatar image

Hi everyone, I am having a pretty small error but I cannot figure out why I am getting it.

//Setup the input
Mat* image=(Mat*)addrImg;
Mat character = *image;
character.convertTo(character,CV_8UC1);
threshold( character, character, 0, 255,1 );
Mat color_dst;
cvtColor(character,color_dst,CV_GRAY2BGR);

I have this code which is in the android jni, the way I am calling cvtColor should only require a one channel image, since I am going from grey to BGR, but I keep getting this error:

01-19 00:37:44.269: E/cv::error()(32379): OpenCV Error: Assertion failed
 (scn == 1 && (dcn == 3 || dcn == 4)) in void 
cv::cvtColor(cv::InputArray, cv::OutputArray, int, int), 
file /home/reports/ci/slave/opencv/modules/imgproc/src/color.cpp, line 3355

It really cannot figure otu why I am getting the error, can anyone help me out here? It would be greatly appreciated.

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answered 2013-01-19 02:45:34 -0500

Vladislav Vinogradov gravatar image

It seems like your image isn't grayscale. convertTo doesn't change channels number, only depth. If you want to convert image to grayscale you should call cvtColor

Mat* image=(Mat*)addrImg;
Mat character;
cvtColor(*image, character, CV_BGR2GRAY);
character.convertTo(character, CV_8U);
threshold(character, character, 0, 255, 1);
Mat color_dst;
cvtColor(character, color_dst, CV_GRAY2BGR);
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Ah that fixed it thanks!

ZachTM gravatar imageZachTM ( 2013-01-19 10:43:58 -0500 )edit
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Asked: 2013-01-18 23:45:14 -0500

Seen: 11,280 times

Last updated: Jan 19 '13