Any method to extract edges from a color image directly without converting it into grayscale image?

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@berak 👉 A Novel Approach for Color Image Edge Detection Using Multidirectional Sobel Filter on HSV Color Space This is what you mean to say I suppose.

did not knew the paper, thanks for the link. the main breadwinner there seems to be the sobel enhancement, but the edge extraction is still done on an intensity image (so no difference to grayscale).

myidea of applying it to hue was more for the case, where there are borders due to different colors (think red and green), but with same intensity (which would vanish with a simple greyscale pass)

so, what do you need to do ? do you want to find contours ? do you want to highlight edges in color images ? (like in that paper ?)

@berak You are welcome. I tried Edge extraction through V it came out similar to the edge extracted from a grayscale image. My interested image doesn't have a lot of red and green in it to detect edges 😅 I need to first extract the edges then only will I be able to think about proceeding to contours.(As it is nearly impossible to design an alogorithm that completes the missing edges for us)

" I tried Edge extraction through V it came out similar" -- yea, expected, unfortunately ;(

Is there any way we can complete the missing edges? I know we only have X and Y coordinate value of the edge. The shape of the edge can be anything which makes things more complicated.

hmm, i'm clearly lacking ideas here, but if you have a contour, you can draw it as a "closed" polygon, or try to find the convex hull of it.

Am I misunderstanding something? Canny edge detection supports multichannel image processing and it should be more stable than converting the image to grayscale before.

The difference to converting the image before is that in the Canny algorithm Sobel is calculated for each channel independent. After that the strongest gradient value for each pixel is chosen out of the channels for further edge detection. The step is done here. So where is the problem here?

But there is a small restriction: For multi channel images inplace-processing is not supported. You have to use another Mat as edge image.

@berak I have created one more question for the broken edge thing. Link

@matman Yup got it working on the color image. I does work on multi channel :) Problem is it still is not able to detect the edges correctly 😅