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rectangle color always gray

asked 2012-12-10 04:43:07 -0500

Rex gravatar image

updated 2012-12-10 04:44:05 -0500

Hi

Silly little problem , but for some reason the method rectangle does not react to the input argument.

This should yield a red box, but the box is always gray no matter what I do to the input arguments of Scalar.

rectangle( CurrentMat, matchLoc, Point( matchLoc.x + TemplateMat.cols , matchLoc.y + TemplateMat.rows ), Scalar(0,0,255), 2, 8, 0);

Any suggestions? TIA.

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Are your CurrentMat grayscale? If CurrentMat is 1-channel mat, rectangle always draw grayscale objects.

Vladislav Vinogradov gravatar imageVladislav Vinogradov ( 2012-12-10 05:04:49 -0500 )edit

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answered 2012-12-10 05:05:59 -0500

Siegfried gravatar image

updated 2012-12-10 05:12:28 -0500

Hi, check the type of your image (CurrentMat). If it is a single channel image, the rectangle will be drawn in gray. Then you can use cv::cvtColor() to convert the image into a RGB image and draw the rectangle in this image.

cv::Mat CurrentMat_RGB;
cv::cvtColor(CurrentMat, CurrentMat_RGB, CV_GRAY2RGB);
rectangle( CurrentMat_RGB, matchLoc, Point( matchLoc.x + TemplateMat.cols , matchLoc.y + TemplateMat.rows ), Scalar(0,0,255), 2, 8, 0);
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Thanks. There was an alpha channel in CurrentMat which caused the problem. Not sure why. CvtColor CV_BGRA2BGR seems to have sorted the problem out.

Rex gravatar imageRex ( 2012-12-10 05:55:49 -0500 )edit
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Asked: 2012-12-10 04:43:07 -0500

Seen: 1,918 times

Last updated: Dec 10 '12