Is it possible to display colored text on a Canny Edge frame?

Question

Please forgive me for the question, I am quite new to OpenCV. I am using canny edge detection on a people-counting program, and every time that a person walks into the frame an ID dot is placed in the center of the person. Before I applied code to generate the canny edges, I displayed the IDs as green, however, with the canny edges I can't see any color. Rather, the IDs are just outlines and nothing else. I would very much like to retain the color, as it would make it a lot easier to see with the black and white background.

Here is a picture of the frame that I have after Canny Edge has occurred

In the bottom left, you can see some text that I would like to be colored, but that has been changed by the edges.

Is it possible to display colored text in conjunction with Canny Edge detection?

Answer 1

I tested using opencv 4.0.1 and it works as expected: you can convert edge output image to bgr image, then put all the colored elements youy need. Here a small example how to do that:

    import cv2 as cv
    img = cv.imread(filename, cv.IMREAD_COLOR) 
    img_gray = cv.cvtColor(img, cv.COLOR_BGR2GRAY)

    filt = cv.medianBlur(img_gray, 9)
    filt = cv.blur(filt, (3, 3))

    edges = cv.Canny(filt, 10, 50)

    edges_bgr = cv.cvtColor(edges, cv.COLOR_GRAY2BGR)
    w,h = edges_bgr.shape[:2]
    center = (int(h/2), int(w/2))
    radius = 100
    cv.circle(edges_bgr, center, radius, (255,128,0), 3)

    font = cv.FONT_HERSHEY_SIMPLEX
    bottomLeftCornerOfText = center
    fontScale = 1
    lineType = 2

    cv.putText(edges_bgr,'Text with colors', 
                bottomLeftCornerOfText, 
                font, 
                fontScale,
                (0,128,255),
                lineType)

    cv.imshow("edges with colors", edges_bgr)