Matlab code for extracting random subwindows/subimages

[amus]

hi,

I am doing project related to object recognition using decision trees and random subwindows.For which i nee d MATLAB code for extracting random subwindows/subimages(size is 16x16) from the image files and after that i need to get the gray values of the subimages.

 

[MATLABdude]

Welcome to PhysicsForums!

I can't supply that code mostly because I don't have any, nor have I done much image processing in the MATLAB environment. I suspect that, for what you're doing, you're going to need to write some code. (i.e. no free lunch, but you never know what the Google is able to turn up)

If you're just starting out, I recommend looking at the following MATLAB page to see how MATLAB deals with image data:
http://www.mathworks.com/access/helpdesk/help/techdoc/creating_plots/f2-145.html

The page I linked to gives an example of how to extract one pixel from a raster image, you should be able to extend this to randomly extract 16x16 pixels out of your image.

 

[oswaler]

Can anyone please help me with this?

I would recommend using the built-in functions in MATLAB to extract random subwindows/subimages from your image files. You can use the "imcrop" function to specify the size of your subimages and the "imread" function to read in your image files. Then, you can use the "randperm" function to generate a random sequence of indices and use them to select random subwindows from your images. Finally, you can use the "rgb2gray" function to convert your subimages to grayscale and obtain the gray values. I would also suggest looking into other image processing functions in MATLAB that may be helpful for your project, such as "imresize" or "imrotate".