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### Highlights fromImage Super-Resolution - Iterative Back Projection Algorithm

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# Image Super-Resolution - Iterative Back Projection Algorithm

19 Nov 2011 (Updated 26 Nov 2011)

A simple maximum-likelihood algorithm for super-resolution.

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Description

This project is a simple implementation of the Iterative Back-Projection (IBP)
algorithm for solving the Super-Resolution problem. It was first proposed
by Michal Irani in her 1991 paper "Improving resolution by image
registration". The imaging model being used is described by a paper by
Michael Elad, "Super-Resolution Reconstruction of an image". Both papers
can easily be found through a search in Google Scholar.

I've done two simplifications to the imaging model:
1) The image blur is assumed to be spatially invariant.
2) The spatial transformation model is a global translation.

To run the example code, follow the following steps:
1) Run SRSetup.m
2) Run SRExample.m

The example code operates on a dataset that is generated synthetically from
a reference image. Thus, the exact values for the blur sigma and the
translation offsets are being used.

Required Products MATLAB
MATLAB release MATLAB 7.11 (R2010b)
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12 Sep 2012

When generating the stack of LowRes Images the code only produces a diagonal shift, since the offsets along x and y are identical.

change the following line in SynthDataset:

offsets(i,:)=2*rand -1 --> offset(i,:)=2*rand(2,1)-1

11 May 2012

Can some one tell me why we model noise as additive Gaussian noise in most of the super-resolution algorithms.

27 Feb 2012

In order to avoid divergence when using a large number of LR images. Try to use a coefficient smaller than 1 (I tried 0.25) in the update equation for x:
x = x + 0.25*res; instead of x = x + res; This ensures smaller (and safer) steps in the Gradient Descent procedure.

05 Jan 2012

well i do add laplasian term as a prior, but i think the problem lies some where else because if you increase number of low resolution images the output destroyed.

05 Jan 2012

Can you please increase the images up to 30 and see the results.

05 Jan 2012

Increasing the number of images causes the solution to suffer from overfit. Adding a prior on the image should help. Search the web for papers on priors for super-resolution.

05 Jan 2012

Well the problem is now on increase the number of low resolution images, if you increase the numImages =10 and run the code the output is not good whats the problem ?

22 Dec 2011

This doesn't run on somebody else's machine without tweaking.

29 Nov 2011

Hello,
The code only deals with translation motion, how to extend it if the low resolution images are also rotated,
still code is not updated.

26 Nov 2011

I posted it. It might take a few days until it will show up here.

26 Nov 2011

Hello victor,
Where is the updated file, kindly post the updated script.

26 Nov 2011

Hi Imi,
the function SynthDataset has an output called croppedOriginal which crops the original image to the size of the super-resolved image. In order to prevent confusion about this, I've updated the example script to include a mean-square error calculation.

25 Nov 2011

Hello,
How to calculate PSNR for comparison purpose, because original image and super-resolved image have different sizes, kindly look into the matter.