使用OpenCV从图像中提取数字

Question

I have Images like these from which I want to extract the Numbers.

I've been working with OpenCV and Template Matching in particular Interested me, but as the technique doesn't account for any image scaling and rotation, I'm out looking for techniques that may be able to take atleast scaling into account.

Please offer any suggestion or help. All operation are in Real Time.

PS Image quality cannot be improved, The camera's capability is as such.

Answer 1

Investigate SIFT : Scale Invariant Feature Transform . OpenCV implements this feature, check: Implementing SIFT in OpenCV .

Also these pages offer valuable content:

• Finding shapes in an image using opencv
• Are there any fast alternatives to SURF and SIFT for scale-invariant feature extraction?
• Sift implementation with OpenCV 2.2
• training SIFT features in OpenCV

Answer 2

To detect these numbers without using SIFT or SURF it is also possible to create a classifier based on the K nearest Neighbour algorithm. You can generate a database of .pbm files and load them into a classifier using a c++ OCR library found here

Step by step:

1: Find a way to extract the numbers from the image using cvFindContours

2: Store these images as png files with cvSaveImage and convert them to binary pbm files

3: Number the .pbm files and store them in seperate folders for each number

4: Load the .pbm files with the library shown above

5: Use the function ocr::classify with the images in real time to get the category they belong to (eg which number).