How can I use BCGTransform function to process 16-Bit Image?

[yuemuping]

Hi~

I'm using LabWindowsCVI8.5 and NI Vision to do the Image processing. When I read the "IMAQ Vision for LabWindowsCVI Reference Manual", I found that the imaqBCGTransform function only supports 8-bit Image, while I have to do the BCG tranform on 16-bit image. Is there any solutions to use BCGTransform function to process 16-Bit Image? Or Is there any other functions which could do the Brightness, Contrast and Gamma correction on 16-bit Image?

Thanks a lot! 

[dummy_decoy · Accepted solution]

given that imaqBCGTransform is implemented as a lookup table, we can understand why it is limited to 8-bit images.

now let's have a look at the definition of each of this terms (from the NI Vision Concepts documentation):

- brightness: A constant added to the red, green, and blue components of a color pixel during the color decoding process; 

- contrast:  A constant multiplication factor applied to the luma and chroma components of a color pixel in the color decoding process.

- gamma correction: Expand the high gray-level information in an image while suppressing low gray-level information.  (the chapter on lookup tables gives some examples of gamma corrections)

now that you understand that this transform is a simple mathematical function, you only have to compute the correction for each pixel on your 16-bit image.

i don't know the exact formula used by the imaqBCGTransform function, but you should be able to approximate it by performing some test on 8 bit images with the original function... or you can roll your own formula... or find one on the net...or you can ask someone at NI to give you the formula...

[yuemuping]

Thanks a lot~ Could you please tell me that is there any example or samples for the lookup table? I still do not know how to create a lookup table and ues it in LabwindowsCVI.