Canny edge detector: Difference between revisions

partition =: 4 : '2 0 3 1 |: ((1{x) ([+\]) (2 0 1|: ((0{x) ([+\]) y)))'

apply =: 4 : '+/"1 (+/"2 (x *"2 y))'

addborder =: (0&,@|:@|.)^:4

normalize =: ]%+/@,

|: w{. w0}. |: h{. h0}. y

)

attach =: 3 : 'max3x3 (3 3 partition (addborder y))'

unique =: 3 : 'y*i.$y'

 

canny =: 3 : 0

NB. Detect the edges (sets of connected points)

 

The above implementation solves the 'inner problem' of Canny Edge Detection in the J, with no external dependencies. Standard libraries provide additional support including interfaces to image file formats and graphic displays.

Image file libraries for different image formats import into and export from a generalized data structure, an array of pixels with three or four color channels. The following code invokes these standard libraries, and also converts between the import format and the monochromatic representation used here for edge detection.

NB. image =: readbmp 'chess.bmp'

NB. image =: readpng 'boat1.png'

NB. image =: readjpeg 'lena.jpg'

NB. select or combine from color channels

NB. if original image is grayscale, take any color channel

green =: 256 | <. image % 256

blue =: 256 | image

load'canny.ijs'

edges =: canny image

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