module Tutorial::EdgeDetection
Overview
Given sample.jpg
image:
We can run the Sobel Operator to detect edges in it:
require "cr-image"
require "cr-image/jpeg"
vertical_sobel = CrImage::IntMap.new([
[-1, -2, -1],
[0, 0, 0],
[1, 2, 1],
])
horizontal_sobel = CrImage::IntMap.new([
[-1, 0, 1],
[-2, 0, 2],
[-1, 0, 1],
])
image = CrImage::GrayscaleImage.open("sample.jpg")
dx = image.cross_correlate(horizontal_sobel)
dy = image.cross_correlate(vertical_sobel)
(dx ** 2 + dy ** 2).to_gray(scale: true).save("edge_detection.jpg")
Results in image:
This script ran on my machine in 11ms
in --release
mode.
Note: This tutorial is using cross_correlate
. For large images (or medium-to-large operators), the cross_correlate_fft
may perform better.