backprojection

With Radon transform, I can rewrite all my Matlab simulations of Computed Tomography and filtered backprojection using Mathematica and Manipulate instead.

Wolfram Blog : The R&D Pipeline for Mathematica 2009

Most of the pit was filled with a 3-D backprojection of the scene below the water but an inset volume gave a wider perspective.

Burning Brightly 2009

In the backprojection image (ignore the red & blue line for now), we can clearly see the target as well as some noise i.e. a vertical line and some area in top left.

The Code Project Latest Articles Arif_Khan 2009

We set the value of the pixel in the backprojection image by using the ratio of the value of target histogram and value of image histogram at the bin index i.e. histT [idx] / histImage / [idx] as shown below.

The Code Project Latest Articles Arif_Khan 2009

Histogram backprojection is a technique used for creating a probability image

The Code Project Latest Articles Arif_Khan 2009

This value is final used to set the pixel value in the backprojection image.

The Code Project Latest Articles Arif_Khan 2009

Using backprojection image and moments we can find the orientation of the target, length and width of the probability distribution.

The Code Project Latest Articles Arif_Khan 2009

In the above code we created a blank backprojection image, create the histogram for the current frame and iterated through the frame pixels.

The Code Project Latest Articles Arif_Khan 2009

One can see that the if the bin values of target and the frame corresponding to a pixel index are the same, the resulting pixel value in backprojection image will be 255.

The Code Project Latest Articles Arif_Khan 2009

The reason to discuss Histogram Backprojection is because i) It is a useful technique to have in the bag ii) You can find some more information about target, like orientation & iii) I am going to implement a simple object tracker using backprojection.

The Code Project Latest Articles Arif_Khan 2009