Hough Transform example: Result of cvtColor()

asked 2016-10-28 21:55:43 -0600

skr_robo
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I am learning to implement Hough transform and I have this example program from OpenCV documentation. It contains the following two lines of code:

Canny(src,dst,50,200,3);
cvtColor(dst,cdst, CV_GRAY2BGR);

I tried displaying both dst and cdst. Both these images look the same. So, I wonder why cvtColor is applied? Is cdst created for the sole purpose of displaying lines detected in dst?

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answered 2016-10-28 22:09:46 -0600

Tetragramm

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It's so that it can draw lines in color. The canny edges are white, but it draws on that cdst image in blue and red to show the lines it detects.

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But the cdst edges are also white. I don't get your point.

skr_robo ( 2016-10-28 22:18:58 -0600 )edit

Look at the tutorial you linked.

line( cdst, pt1, pt2, Scalar(0,0,255), 3, CV_AA);

This draws on the image. But if it were to draw on dst, it could only draw a white line on top of the existing white lines because there's only one channel. With three channels in cdst, it can draw in colors, in this case, red.

Tetragramm ( 2016-10-29 00:05:38 -0600 )edit

Thank you for the explanation.

skr_robo ( 2016-10-31 22:08:40 -0600 )edit

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Asked: 2016-10-28 21:55:43 -0600

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Last updated: Oct 28 '16

Hough Transform example: Result of cvtColor() edit