RGB to HSV and thresholding

Source code notebook Author Update time

This example illustrates how RGB to HSV (Hue, Saturation, Value) conversion can be used to facilitate segmentation processes.

using Images, TestImages, LinearAlgebra

rgb_img = testimage("lighthouse")
hsv_img = HSV.(rgb_img)
channels = channelview(float.(hsv_img))
hue_img = channels[1,:,:]
value_img = channels[3,:,:]
saturation_img = channels[2,:,:]

A simple segmentation of the image can then be effectively performed by a mere thresholding of the HSV channels.

mask = zeros(size(hue_img))
h, s, v = 80, 150, 150
for ind in eachindex(hue_img)
    if hue_img[ind] <= h && saturation_img[ind] <= s/255 && value_img[ind] <= v/255
        mask[ind] = 1
binary_img = colorview(Gray, mask)

The obtained binary image can be used as a mask on the original RGB image.

segmented_img = mask .* rgb_img

hcat(rgb_img, binary_img, segmented_img)

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