MATLAB: How does the function “imresize” work in details

enhancementimageimage processingimprovementimresizeresolutionresolution increasing

During my internship I discovered the function "imresize" which I used it to enhance the resolution of images (for example : I transformed a 32×32 image into a 128×128 image) and it gave me really good results.

So I read the code of the function and it didn't help me to understand it.

So I am asking you to explain to me how it works or to give me links to articles and publications on resolution enhancement theories. The second choice would be better for me.

Thanks to all and sorry for my english.

BELAFDIL Chakib

Best Answer

I'm not sure, (did'nt look at the function's code). but, probably using some kind of bi-linear interrpolation: http://en.wikipedia.org/wiki/Bilinear_interpolation

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MATLAB: What exactly happend when you use the command imresize

This question has essentially been asked before:

http://www.mathworks.com/matlabcentral/answers/82893-how-does-the-function-imresize-work-in-details

In short, resizing is a geometric transformation, or more precisely a scale transformation. For each pixel in the output image, imresize is doing a point transformation to find where the corresponding point maps in the input image. Once imresize has formed a collection of remapped points, interpolatation is performed to resolve sub-pixel remapped locations (the default of imresize is bicubic interpolation).

If the output image is being scaled with a scale factor less than 1, then by default a low-pass anti-aliasing filter is applied to the input image prior to the steps described above to prevent high frequency content from the input image introducing distortions due to downsampling the input image. You can turn this anti-aliasing filtering off to see how it effects results. It's generally a very important step when down sizing an image to get visually nice looking resized images.

MATLAB: Please tell me about image interpolation.

scale = alpha;
newimage = imresize(YourImage, scale);

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MATLAB: What exactly happend when you use the command imresize

MATLAB: Please tell me about image interpolation.

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