Cut an area in binary Image

Question

Nour 2014-12-21

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/167447-cut-an-area-in-binary-image

评论： Image Analyst 2015-2-14

1.png

Hi Everybody, Please, I would like to cut the white pixels area from a binary image, so that the output will be this white area. From another question, I see a method that shows how to surround this area, but also I would like to cut automatically the part surrounded, which is a vehicle logo in my case. Here is the link to this method: http://www.mathworks.com/matlabcentral/answers/24041-cut-an-image

I've tried this method for some hours, and trying to edit it to see the results, but until now I even didnt get the surrounded line, please your help is welcome.

Thanks!

Nour.

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Nour 2014-12-21

编辑：Nour 2014-12-21

2.png

Here is what I expect as output

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Answer 1

Image Analyst 2014-12-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/167447-cut-an-area-in-binary-image#answer_162991

在 MATLAB Online 中打开

There are several ways to crop the image. For example you can use regionprops() to find the bounding box, like I show in my Image Segmentation Tutorial http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862.

Or you could simply find the min and max rows and columns:

[rows, columns] = find(binaryImage);
topRow = min(rows);
bottomRow = max(rows);
leftColumn = min(columns);
rightColumn = max(columns);
croppedImage = binaryImage(topRow:bottomRow, leftColumn:rightColumn);

You could also find the bounding box by summing vertically and horizontally and then using find() like above.

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Image Analyst 2014-12-21

编辑：Image Analyst 2014-12-21

在 MATLAB Online 中打开

Here, I did it for you. In the code below IS my suggestion that you left out, and it produces the image shown below that.

% Read in original RGB image.
rgbImage = imread('C:\Users\Nour\Documents\Temporary\L1.jpg');
subplot(2, 2, 1);
imshow(rgbImage);
axis on;
fontSize = 30;
title('Original color image with white border', 'FontSize', fontSize);
% Convert to binary.
binaryImage = rgb2gray(rgbImage) > 128;
% Get rid of white border.
binaryImage = imclearborder(binaryImage);
subplot(2, 2, 2);
imshow(binaryImage);
axis on;
title('Binary Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 
% Find bounding box.
[rows, columns] = find(binaryImage);
topRow = min(rows);
bottomRow = max(rows);
leftColumn = min(columns);
rightColumn = max(columns);
% Crop the image.
croppedImage = binaryImage(topRow:bottomRow, leftColumn:rightColumn);
% Show cropped image
subplot(2, 2, 3);
imshow(croppedImage);
axis on;
title('Cropped Image', 'FontSize', fontSize);

Image Analyst 2015-1-4

编辑：Image Analyst 2015-1-4

在 MATLAB Online 中打开

rows is a column vector so you need a semicolon and you need to use the size of the image inside some of the max and min. Corrected code/demo is below:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;
grayImage = mat2gray(peaks(300));
subplot(2, 2, 1);
imshow(grayImage, []);
axis on;
title('Original Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
binaryImage = grayImage > 0.75;
subplot(2, 2, 2);
imshow(binaryImage, []);
axis on;
title('Binary Image', 'FontSize', fontSize);
% Determine Cropping box.
[rowsInImage, columnsInImage] = size(binaryImage);
[rows, columns] = find(binaryImage);
margin = 10;
topRow = max([1; min(rows) - margin]);
bottomRow = min([rowsInImage; max(rows) + margin]);
leftColumn = max([1; min(columns) - margin]);
rightColumn = min([columnsInImage; max(columns) + margin]);
% Crop original and show it.
croppedOriginalImage = grayImage(topRow:bottomRow, leftColumn:rightColumn);
subplot(2, 2, 3);
imshow(croppedOriginalImage, []);
axis on;
title('Cropped Original Image', 'FontSize', fontSize);
% Crop binary and show it.
croppedBinaryImage = binaryImage(topRow:bottomRow, leftColumn:rightColumn);
subplot(2, 2, 4);
imshow(croppedBinaryImage, []);
axis on;
title('Cropped Binary Image', 'FontSize', fontSize);

If this works now, please "Accept" the answer.

Nour 2015-2-14

Hi, I've tried export_fig() few days ago, but I got some errors, actually I think I don't understand how to use it, please if you can help me with that.

Which File Exchange?

Thanks!