How to change all the colours in the image to black

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Elysi Cochin
Elysi Cochin on 26 Jan 2021
Answered: yanqi liu on 1 Feb 2021
how to change all the colours in the image to black except the white colour in image?

Accepted Answer

Timo Dietz
Timo Dietz on 26 Jan 2021
Edited: Timo Dietz on 26 Jan 2021
Try this:
imageData = imread([yourFile]);
% split R, G, B
imgR = imageData(:, :, 1);
imgG = imageData(:, :, 2);
imgB = imageData(:, :, 3);
% get linear index of all pixels with color not white
colIdx = (imgR < 1 | imgG < 1 | imgB < 1);
% change color to black
imgR(colIdx) = 0;
imgG(colIdx) = 0;
imgB(colIdx) = 0;
% write back to new image data or overwrite the origin imageData
newImage(:, :, 1) = imgR;
newImage(:, :, 2) = imgG;
newImage(:, :, 3) = imgB;

More Answers (1)

yanqi liu
yanqi liu on 1 Feb 2021
clc; clear all; close all;
I = imread('ceshi.png');
I2 = rgb2hsv(I);
s = mat2gray(I2(:,:,2));
bw = im2bw(s, 0.5);
figure; imshow(~bw)

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