MATLAB: Image comparison and compression

image compressionimage processing

I am doing project based on image comparison. I need to compare two images. I use basic pixel by pixel comparison . If the images are of different size the comparison can not be done. So i was planning to compress the image to make them of same size(Resolution). But while compressing the image the pixel value might change (i am not sure about whether they will change or not ? correct me if im wrong) So in that circumstances pixel by pixel comparison may not be an efficient method. Can any one please help me with this. Please.

Best Answer

I think you mean "resize" rather than "compress".
Yes, resizing images will generally change pixels.
What you should do about the change of pixels depends upon what you mean by "image comparison".
If I have a picture that is a green background (square) that has a purple circle and an orange triangle inside it, and I create a second image in which I leave all the sizes and shapes exactly the same, but change the colors to yellow, red, and brown, then should the images compare as being fairly similar (same object shapes, same sizes and positions), or should the images compare as being completely different (since not one pixel is the same color) ?
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