Detect Edges – Canny

Before After

 

Detect Edges – Canny deletes areas of color, leaving just the boundaries displayed in black between them.

This option will operate in much the same was as the Detect Edges – Simple option where you have clearly discernable areas of solid color.

However – Not all images will have clearly distinct color areas and therefore accurately identifying the boundary may be a little more difficult. This is especially so in grayscale images which lack good contrast between the colors.

Canny edge detection is more complex than the Simple method in that, with suitable setting of the Canny parameters, it should be possible to detect edges in the worst of images.

The edge detection takes place on the whole image.

 

The Canny Edge Detection Parameters

The Canny Edge Detector dialog allows the following 3 parameters to be varied as required with the results being displayed in The Preview Window

· Feature Definition

Set between High (40) and Low (250) – Set towards the High value to retain some of the images finer detail – set towards Low to reduce the finer detail which may simply be noise in the image.

· High Threshold

Set between Min (60) and Max (100) – Setting the value too low may increase the number of spurious and unwanted edge fragments appearing in the output.

· Low Threshold

Set between Min (10) and Max (60) – Setting the value too high may cause edges to break up.

The user can readily experiment with the most appropriate settings for their image.

 

To use select Raster Effects Menu > Detect Edges > Canny.

 

Click to undo.

 

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