batch-process images by pasting each onto a central background image

I have a large number (> 1,000) images of different sizes ("the figures") and want to paste each image centrally onto a background image of the same size and save as a new image. The figure images are greyscale and the background is a uniform greyscale image.

I tried the padarray function to pad each image on all sides with a background colour, but this function does not work on my hardware due to graphic card incompatibility.

I also found on here code (by Image Analyst) to do this manually but this is not feasible for the large set I need to process.

My question: Is there a way to automatically paste an image centrally onto another image ?

Answer 1

[Kushagr Gupta]

The following code can help replace central portion of a larger image (uniform background) with another smaller (actual image).

%Using an example to solve the problem
B = imread('cameraman.tif');
A = zeros(512,'like',B);

% Assuming large image is A
szA = size(A);

% Assuming smaller image is B
szB = size(B);

centerA = floor(szA(1:2)/2+1);
centerWindow = floor(szB(1:2)/2+1);

offset = centerA - centerWindow + 1;

R = offset(1);
C = offset(2);

H = szB(1);
W = szB(2);

% Replace central portion of larger image with the smaller one
A(R:(R+H-1),C:(C+H-1),:) = B;

% Display the new image
imshow(A)

This can be converted into a function which can be passed the background and central image as parameters. This function can then be called in a loop to automate the entire process.

Hope this helps.