• Programming 11.12.2008

    I completely recoded the Image Manipulation program. It is now better structured and easier to use. Additionally I implemented the Canny Edge Detector Algorithm and some more filters. 8-bit BMP’s are still not supported, so that would be the next step.

    Binary edge image output from canny algorithm

    Binary edge image output from canny algorithm

    To test the edge detector, I used the image from the Wikipedia article on the topic, as the desired result was known for that image.

    Complete C++ code can be downloaded here (executable included).

    Executing the program without parameters displays the help.

    To perform edge detection on an image, use the following parameter sequence:

    image <input.bmp> <output.bmp> -g -f 0.8 -e -n 80 -w 80 50

    This command first converts the image to greyscale (-g), then applys gaussian blur with a standard deviation of 0.8 (-f 0.8). After that, Sobel filters for X and Y direction are convoluted with the image, which gives an edge image. Those edges are now thinned by Non-Maximum-Suppression (-n 80),  which only leaves one-pixel wide edges, which are above the given threshold. Finally the edge tracer (-w 80 50) deletes pixels not belonging to an edge, by appling hysteresis thresholding.

    Posted by Konstantin @ 15:10

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