HOW TO CROP AN IMAGE

Dear all,

I've an image saved in a uint8 variable and I want to remove the zeros from it (the zeros are the black spaces of the image) to obtain only the image without black space.

I've tried this but it doesn't work because instead of removing the black spaces, it takes away the colors of the image :

TOT=sum(IMG);
tolgo=find(TOT==0);
IMG(:,tolgo)=[];

TOT=sum(IMG');
tolgo=find(TOT'==0);
IMG(tolgo,:)=[];

Thanks.

Answer 1

[KALYAN ACHARJYA]

 %Try this one for Gray Image
 image(image(:, :)=0, :)=[]

[federica pasquali]

Thanks but it doesn't work. I'll send you the image. Thanks again.

[KALYAN ACHARJYA]

rgb_image=imread('prova.jpg');
mask=repmat(all(~rgb_image,3),[1 1 3]); 
rgb_image(mask)=255; 
imshow(rgb_image);

Are you looking this one-

[federica pasquali]

really really thanks! you were so kind!

[Image Analyst]

This doesn't just crop off the black padding on the sides, it actually changes the colors in the image itself. Just look at the comparison.

It just changes black pixels to white pixels and doesn't do any cropping. But, since you accepted the answer, I guess it's what you wanted, though not what I was about to give you code for, which was to crop off the black padding on the left and right while leaving the center of the image intact with the same colors.

[federica pasquali]

I appreciate all the help willingly since I could not do it, if you want to give me a hand, I'm grateful

[federica pasquali]

preferably I would like to remove the black parts and keep the clear image as much as possible

[Image Analyst]

A hand doing what? Evidently this code already does what you want because you accepted it. Do you have a second question? We're willing to help with that. If it's not a followup question to this one, then just post the new question in a new post.

Answer 2

[Image Analyst]

Here is code to crop away the rectangular black padding on the edges of the image:

% Code to crop off any black padding on the edges of the image.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clearvars;
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;

%=======================================================================================
% Read in image.
fullFileName = fullfile(pwd, 'prova.jpg');
[folder, baseFileName, ext] = fileparts(fullFileName);
rgbImage = imread(fullFileName);
% Shrink it to speed it up
% rgbImage = imresize(rgbImage, 0.75);
% Get the dimensions of the image.
[rows, columns, numberOfColorChannels] = size(rgbImage);
% Display the original image.
subplot(2, 2, 1);
imshow(rgbImage, []);
axis on;
caption = sprintf('Original Color Image, %s: %d rows by %d columns', baseFileName, rows, columns);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.

% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0.05 1 0.95]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')

% Get a mask by finding all pixels that are pure black (0,0,0).
blackPixels = max(rgbImage, [], 3) > 0;
% Display the original image.
subplot(2, 2, 2);
imshow(blackPixels, []);
axis on;
caption = sprintf('Black Pixels');
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.

% Find coordinates of all non-black pixels.
[blackRows, blackColumns] = find(blackPixels);

% Crop the image.
croppedImage = rgbImage(blackRows(1):blackRows(end), blackColumns(1):blackColumns(end), :); % Crop
% Get the dimensions of the image.
[rows2, columns2, numberOfColorChannels] = size(croppedImage);
% Display the cropped image.
subplot(2, 2, 3);
imshow(croppedImage, []);
axis on;
caption = sprintf('Cropped Image, %s: %d rows by %d columns', baseFileName, rows2, columns2);
title(caption, 'FontSize', fontSize, 'Interpreter', 'None');
drawnow;
hp = impixelinfo(); % Set up status line to see values when you mouse over the image.

Note: no colors interior to the cropping rectangle are altered.