MATLAB: Auto Crop the image

cropimage

How can I automatically crop these types of images, to get just the rectangle part?

Best Answer

I understand that you would like to crop the rectangular object from the image automatically. I hope the following code would help you do the same

% Read the image
grayImage = imread(filename);
% Display the image.
imshow(grayImage);
S = regionprops(grayImage,'BoundingBox','Area');
[MaxArea,MaxIndex] = max(vertcat(S.Area));
imshow(grayImage,'InitialMagnification',20)
%// Highlight the required object
hold on
rectangle('Position',S(MaxIndex).BoundingBox,'LineWidth',2,'EdgeColor','y')
Length = S(MaxIndex).BoundingBox(3);
Height = S(MaxIndex).BoundingBox(4);
% Cropping the image
% Get all rows and columns where the image is nonzero
[nonZeroRows,nonZeroColumns] = find(grayImage);
% Get the cropping parameters
topRow = min(nonZeroRows(:));
bottomRow = max(nonZeroRows(:));
leftColumn = min(nonZeroColumns(:));
rightColumn = max(nonZeroColumns(:));
% Extract a cropped image from the original.
croppedImage = grayImage(topRow:bottomRow, leftColumn:rightColumn);
% Display the original gray scale image.
figure
imshow(croppedImage, []);

Related Solutions

MATLAB: Crop dark area and display the face only

Convert to grayscale and then threshold and find the bounding box

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
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;
% Read in the color image.
folder = pwd;
baseFileName = 'm2.bmp';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
  % Didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
rgbImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 3.
[rows, columns, numberOfColorBands] = size(rgbImage);
% Display the original color image.
subplot(2, 3, 1);
imshow(rgbImage, []);
axis on;
title('Original Color Image', 'FontSize', fontSize);
drawnow;
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Histogram the red channel, but there is a huge spike at 255 so let's not count those.
subplot(2, 3, 2);
grayImage = rgb2gray(rgbImage);
imshow(grayImage, []);
title('Gray Scale version', 'FontSize', fontSize);
subplot(2, 3, 3);
histogram(grayImage(grayImage<255))
grid on;
title('Histogram of Gray Scale Image', 'FontSize', fontSize);
someThresholdValue = 150;
binaryImage = grayImage > someThresholdValue;
% Take largest blob
binaryImage = bwareafilt(binaryImage, 1);
subplot(2, 3, 4);
imshow(binaryImage);
grid on;
title('Binary Image', 'FontSize', fontSize);
% Label the binary image.
labeledImage = bwlabel(binaryImage);
props = regionprops(labeledImage, 'BoundingBox');
bbox = props.BoundingBox
croppedImageRGB = imcrop(rgbImage, bbox);
subplot(2, 3, 5);
imshow(croppedImageRGB);
grid on;
title('Cropped RGB Image', 'FontSize', fontSize);
% Gray scale version of cropped image
croppedImageGray = imcrop(grayImage, bbox);
subplot(2, 3, 6);
imshow(croppedImageGray);
grid on;
title('Cropped Gray Scale Image', 'FontSize', fontSize);

MATLAB: How can i conver this code to do the same thing fo white background

Try this:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures if you have the Image Processing Toolbox.
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 15;
% Read in a standard MATLAB color demo image.
folder = 'D:\Temporary stuff';
baseFileName = 'test.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
if ~exist(fullFileName, 'file')
  % Didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
grayImage = imread(fullFileName);
% Get the dimensions of the image.  numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
% Display the original image.
subplot(2, 2, 1);
imshow(grayImage);
axis on;
title('Original Gray Scale Image', 'FontSize', fontSize);
% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);
% Find the mask
mask = ~(grayImage == 255);
% Get rid of small junk.
mask = bwareaopen(mask, 2500);
% Display the image.


subplot(2, 2, 2);
imshow(mask);
axis on;
title('Mask Image', 'FontSize', fontSize);
% Call regionprops to get the Bounding Box.
measurements = regionprops(mask, 'BoundingBox');
% Crop out the masked part
thisBoundingBox = measurements(1).BoundingBox
croppedImage = imcrop(grayImage, thisBoundingBox);
% Display the image.
subplot(2, 2, 3);
imshow(croppedImage);
axis on;
title('Cropped Image', 'FontSize', fontSize);
% Make another version with the background black
smallMask = croppedImage >= 251;
croppedImage2 = croppedImage; % Initialize.
croppedImage2(smallMask) = 0;
% Display the image.
subplot(2, 2, 4);
imshow(croppedImage2);
axis on;
title('Cropped Image', 'FontSize', fontSize);
msgbox('Results would be better if you use a PNG image instead of a JPG image.');

Best Answer

Related Solutions

MATLAB: Crop dark area and display the face only

MATLAB: How can i conver this code to do the same thing fo white background

Related Question