OpenCV detect numbers

Question

I\'m using OpenCV on the iPhone and need to detect numbers in an image. I split the image into smaller images so each image has only one number (1-9). All numbers are printe

Answer 1

HOG + SVM (Try to play with kernels)

Answer 2

If the numbers are printed, the job is quite simple, you just need to figure out a nice set of features to match. If the numbers are one font, you can get away with this approach:

• Extract the number
• Find the bounding box
• Scale the image down to something like 10x8, try to match the aspect ratio

• Do this for a small training set, take the 'average' image for each number

• For new images, follow the steps above, but the last is just a absolute image difference with each of the number-templates. Then take the sum of the differences (pixels in the difference image). The one with the minimum is your number.

All above are basic OpenCV operations.

Answer 3

Simple Digit Recognition OCR in OpenCV-Python

This might help you out. Converting the code from Python to C++ is not a difficult task, since OpenCV API's are same for the both.

Answer 4

Convolution Neural Networks are by far the best algorithms for hand written digits. The are implemented in most systems like USPS etc. Here are few papers explaining the algorithms. http://yann.lecun.com/exdb/lenet/

Answer 5

You could start by reading about Principal Component Analysis (PCA), Fisher's Linear Discriminant Analysis (LDA), and Support Vector Machines (SVMs). These are classification methods that are extremely useful for OCR, and there are libraries in any language including C++, Python, C# etc.

It turns out that OpenCV already includes excellent implementations on PCAs and SVMs. I haven't seen any OpenCV code examples for OCR, but you can use some modified version of face classification to perform character classification. An excellent resource for face recognition code for OpenCV is this website.

Answer 6

Objective C++? Try renaming your .m files to .mm and you can then use c++ in your iPhone project.