Question

i am implementing sliding windows technique to develop photo OCR,i.e.,a rectangule of a specific size is cut from the picture and checked if it contains text or not. Then again the rectangle is shifted by some pixels. But this sliding windows technique is taking a lot of time. For example to process a picture of 1366×768 it takes 6 hours with a step size of 2 and window size of 20×25. Is there any other technique which could be helpful or how to speed up the process?

i am coding in java.

Answer 1

It is hard to give a specific recommendation without knowing any details of your algorithm/code. There are several potential performance improvements you could consider:

1. Minimize disk I/O and cache misses. You stated that a rectangle is “cut from the picture”. If each “cut” is a separate read from disk, it is very inefficient and would contribute significantly to execution time. When you shift your window (by 2 pixels, it appears), most of the data in the new window is the same so try to avoid re-reading that data as much as possible.
2. Decrease your window size or increase your step size. This obviously affects your result but depending on the size of the characters you are trying to OCR, it might be an option.
3. If you are applying a convolution filter to do OCR, consider doing fast convolution via a 2D FFT of the image data.
4. Multithread your application, if it isn’t already. While your problem is not embarrassingly parallel, it could be fairly easily multithreaded.