How to use looping method to crop image dynamically (auto-cropping)?

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Dayangku Nur Faizah Pengiran Mohamad
回答： Tejas 2024-8-13
Hello. How to crop image using dynamic cropping method in matlab? Is there any example implementation codes?
Lets say, my original image have two different sizes which are 482 x 841 pixels and 608 x 865 pixels, so can I use loop step at first to extend the pixels which those that not enough pixels if I want to crop into 512 x 512 pixels? If the image size is enough to crop into 512 x512 pixels so no need to extend the pixels. I recently use this code:-
%To read input image
I=imread('1_776.jpg');
imfinfo('1_776.jpg')
First image, image size 482 x 841 px
Second image, image size 608 x 865 px
%To resize image
out = padarray(I, [10 10], 0, 'both');
imshow(out);
imwrite(out,'resize1.jpg');
but this is manual. Now I want it to automatically crop only specific area.
  1 个评论
Rik
Rik 2024-7-2
So you want to crop images if they exceed 512 pixels in either height or width, and want to pad them with black if they are smaller than 512x512?

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回答（1 个）

Tejas
Tejas 2024-8-13
Hello Dayangku,
I am assuming you want to automate the process of resizing images to 512 x 512 pixels by adding padding if any dimension is smaller than 512 pixels and cropping if any dimension exceeds 512 pixels.
To achieve this, follow the steps below:
  • List the names of the images to be resized in a cell array.
  • Loop through each image in the cell array.
  • Check if the image’s rows or columns require padding.
  • Add padding to the rows or columns if necessary.
  • Crop the image to the desired size using the ‘imcrop’ function.
  • Save the cropped image using the ‘imwrite’ function.
The code snippet below demonstrates how this can be done:
% Add the names of images to be resized
listOfImages = {'I1.jpeg', 'I2.jpeg'};
desiredCropSize = [512, 512];
for itr = 1:length(listOfImages)
% Read image based on current index
I = imread(listOfImages{itr});
[rows, cols, ~] = size(I);
% Check if row/column require padding
if rows < desiredCropSize(1) || cols < desiredCropSize(2)
% Calculate padding sizes
padRows = max(0, desiredCropSize(1) - rows);
padCols = max(0, desiredCropSize(2) - cols);
% Evenly add padding to the image. Image is padded twice
% to deal with odd number of padRows/padCols
I = padarray(I, [ceil(padRows/2), ceil(padCols/2)], 'both');
I = padarray(I, [floor(padRows/2), floor(padCols/2)], 'both');
end
% Crop the image to the desired size
croppedImage = imcrop(I, [1, 1, desiredCropSize(2)-1, desiredCropSize(1)-1]);
% Display the cropped image
imshow(croppedImage);
% Save the cropped images
outputFileName = sprintf('Image_%d_resized.jpg', itr);
imwrite(croppedImage, outputFileName);
imfinfo(outputFileName)
end
For a better understanding of the functions ‘imcrop’ and ‘for’, refer to the following links:

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