Wednesday, January 25, 2006

a new angle

I’ve been looking at “Image Mosaicing and Super-resolution”, which is the thesis for David Peter Capel, on recommendation of Serge.

After consideration, I believe following this thesis will be more beneficial and a better use of my time than trying to use my previous papers. The reason that I believe this is because the thesis brings together all of the elements that I need to implement into one unified framework. Rather than trying to use bits and pieces that I’ve found in different papers, I can hopefully use a single paper, albeit a long one. In this way I’ll have everything I need to start off with in one place, and later on if I want to make improvements based on other papers I will be able to start from a solid foundation.

Based on this thesis, the three major steps I will need to implement are as follows:
1.) Image registration : aligning overlapping images accurately.
2.) Image mosaicing : putting multiple overlapping images into a single image.
3.) Super-resolution : using extra information gained from overlapping images to extract a higher resolution image which will contain more fine detail.

The next steps that I will take towards accomplishing these three items will be to implement the method of image registration from the thesis and apply it to synthetic low resolution image sets that I will create from high resolution images.

Saturday, January 21, 2006

failed start

As my first step in starting this project I picked one paper:

super-resolution from multiple images having arbitrary mutual motion - zomet, peleg
-http://www.cs.huji.ac.il/~peleg/papers/supres-book.pdf

At first look this paper was promising as a basis for an algorithm. It had simple concise mathematical equations that made a lot of sense for the super-resolution step, and a straight forward explanation of the ideas behind their super-resolution algorithm. They use a model based algorithm which is basically as follows:
Low resolution images are the result of projecting a high resolution image onto a plane, then sampling.
The goal is to use these low resolution images to find a high resolution image to fit this model.

The actual formulation of the super resolution algorithm was as a large sparse optimization problem. First a form of steepest decent was talked about, then a more effective conjugant gradient method was discussed. Here is the basic formulation:



-xL is the nth low resolution image reordered as a vector.
-xH is the high resolution image reordered as a vector.
-Wn is the geometric warp matrix.
-Hn is the blurring matrix.
-D is the decimation matrix.

Then the solution could be found by minimizing

where A = DHnWn



Unfortunately much of the details that seemed clear in concept where hidden in this paper. Things such as the Wn geometric warp matrix where side stepped by saying that they were beyond the scope of the paper, which was really focused on the conjugant gradient portion of the super resolution algorithm.

I have begun following up on two of the papers that where referenced in the geometric transformation section:
“True multi-image alignment and its application to mosaicing and lens distortion correction” by H.S. Sawhney and R. Kumar
“Multi-Frame Estimation of Planar Motion” by L Zelnik-Manor and M. Irani

Wednesday, January 11, 2006

In the beggining...

Here is the first post for my blog. I'll start by linking the papers that I'm looking at and the page where i'll be getting the video files for my first data set.

video sequence:
-http://www.cs.huji.ac.il/~zomet/superResolution.html

papers:
Super-Resolution Enhancement of Text Image Sequences - Capel & zisserman
-http://www.robots.ox.ac.uk/~vgg/publications/papers/capel00.pdf
Automated mosaicin with super-resolution zoom - capel and zisserman
-http://citeseer.ist.psu.edu/cache/papers/cs/2287/http:zSzzSzimogen.robots.ox.ac.uk:20000zSz~vggzSzvggpaperszSzCapel98.pdf/capel98automated.pdf
Robust super resolution - zomet, rav-acha, peleg
-http://www.cs.huji.ac.il/~peleg/papers/cvpr01-RobustSR.pdf
super-resolution from multiple images having arbitrary mutual motion - zomet, peleg
-http://www.cs.huji.ac.il/~peleg/papers/supres-book.pdf
mosaicing from a translating camera, with efficient application of super-resolution - zomet (thesis)
-http://www.cs.huji.ac.il/~zomet/thesis.pdf