Laplace Operator

Laplacian operator is a basic function used to find edges in image. You'll find here https://docs.opencv.org/3.4/d5/db5/tutorial_laplace_operator.html all mathematical explanations about this operator. This code illustrates how it's easy to use Lapace operator with Rebol-OpenCV extension.

#!/usr/local/bin/r3
Rebol [
]
;-- see: https://docs.opencv.org/3.4/d5/db5/tutorial_laplace_operator.html
 
kSize: 3
scale: 1
delta: 0
cv: import opencv
with cv [
ddepth: CV_16S
img: imread %../../image/lena.jpg ;--read image as matrix
gray: Matrix img ;--make grayscale matrix
        dst:  Matrix img ;--make destination matrix
namedWindow  src: "Source" ;--create source window
namedWindow  lap: "Laplacian" ;--create destination windows
moveWindow src 0x10 ;--move source window
moveWindow lap 260x10 ;--move destination window
GaussianBlur img img 3x3 0 0 ;--reduce noise with a Gaussian filter
cvtColor :img :gray COLOR_BGR2GRAY ;--make a grayscale matrix
Laplacian :gray :dst ddepth kSize scale delta         ;--Laplacian filter
convertScaleAbs :dst :dst 1 0 ;--we need a 8-bit image
imshow/name img src ;--show source window
imshow/name dst lap ;--show destination window
waitKey 0 ;--wait for keypress
    destroyAllWindows ;--clear all window
]

Result: