Image contrast and brightness controlling by measuring histogram of image

[Ketan Patel]

Hello friends....I am doing Train number recognition by Vision Builder and Vision Developement module. I am using NI 1742 smart camera at remote location.

Softwares:  LabVIEW 8.5

 LabVIEW RT 8.5

 Vision Developement Module 8.5

 Vision Acquisition Software 8.5

 Vision Builder 3.5

I have made some experiment in Vision Builder and make one program for recognition of number and after that convert in LabVIEW code. But i have got some problem regarding light intensity difference. I want to make program that will be independent of light difference. So is there any algorithm that will measure histogram of an image and according to that it will adjust contrast and brightness of image so number will be easily recognized.

If do you have anyother solution please help me..... 

[P@Anand]

Have you tried the Examples that comes along with the vision module...? You have Optical Character Recognition (OCR.vi) vi available.. Try looking at it and make some intensity difference (as you said and if needed) in the same and execute it.. It works good...

[Ketan Patel]

Thank for reply.......but i need automatic controlling of brightness & contrast of image means in night vision, all images captured are so dark, so i want some algorithm like it will generate histogram of an image and take automatically decision to make brightness & contrast adjustment for better vision in night...

Can u tell me where those examples are given???

[Falcon177]

Hello,

I had a similar problem when I was working on an inspection project. I has a red illumination on the inspection zone and when combined with the normal surrounding light it varies significantly and affects the results of the OCR and color detection. So what we did is take a small background portion of the image analyse its histogram and colors and based on this data indicate the correction that need to be made on the image, so I advice you to do the same, take pictures in different lighting conditions then analyse those images and find the general characteristics of images taken in each lighting condition like brightness and contrast, you'll find that images taken in same lighting conditions have some common values regardless of their nature, then use these values to regulate the brightness and contrast as you wish..

Take care, If you need more explanation you're welcome