how can i rescale image? standard is at the center part

hello, i want to rescale image using the center standard, not at the corner of the imge

I attatched the example image, the red square is the reference image, and the blue one is the rescaled image (here, the center part is marked as 'X', and not only this enlarging case, i want to apply this algorithm for reduction case)

i want to use affine transform or any other method using interpolation, and i want to input the ratio of rescale and output of the rescaled image

I repreciate to all of your answers thanks a lot :))

[Umar]

Hi Dayeon,

I have implemented the code based on your request. It rescales an image by a specified ratio, centers the original image within the rescaled image, and visually compares the original and rescaled images for analysis or visualization purposes. Here is the example code snippet,

% Read the original image

originalImage = imread('/MATLAB Drive/IMG_7116.JPG');

% Define the rescale ratio (e.g., 2 for doubling the size)

rescaleRatio = 2;

% Calculate the new dimensions based on the rescale ratio

newHeight = round(size(originalImage, 1) * rescaleRatio);

newWidth = round(size(originalImage, 2) * rescaleRatio);

% Create a new blank image with the new dimensions

rescaledImage = uint8(zeros(newHeight, newWidth, size(originalImage, 3)));

% Calculate the center of the rescaled image

centerX = round(newWidth / 2);

centerY = round(newHeight / 2);

% Calculate the starting and ending points for copying the original image to the center of the rescaled image

startX = max(1, round(centerX - size(originalImage, 2) / 2));

endX = min(newWidth, startX + size(originalImage, 2) - 1);

startY = max(1, round(centerY - size(originalImage, 1) / 2));

endY = min(newHeight, startY + size(originalImage, 1) - 1);

% Copy the original image to the center of the rescaled image

rescaledImage(startY:endY, startX:endX, :) = originalImage;

% Display the original and rescaled images

figure;

subplot(1, 2, 1);

imshow(originalImage);

title('Original Image');

subplot(1, 2, 2);

imshow(rescaledImage);

title('Rescaled Image with Center Standard');

Please see attached.

Feel free to modify the code based on your preferences. I hope this answers your question.

[dayeon]

thank you for your amazing code! thank a lot! :))

[Umar]

Hi dayeon,

You're welcome, if the Answer resolved your question, please Accept-click it.

Answer 1

[Matt J]

Use imresize. It scales relative to the center.

Answer 2

[Angelo Yeo]

It looks like you want to apply affine transfomation to image and warp them. You can use imwarp to apply geometric transformations and interpolate them.

I = imread('cameraman.tif');
imshow(I)

A = [1 0.5 0; 
    0 1 0; 
    0 0 1];
tform = affinetform2d(A);
J = imwarp(I,tform);
imshow(J)