Why do I need pdf when make histogram equalizaion

Hi all,

I searched about histogram equalization without histeq(), but it seems many codes actually don't use pdf(probability distribution funtion)when get cdf or something, and they just say they need pdf.

What is the role of pdf when make histogram equaliztion?

Thanks.

Answer 1

[Image Analyst]

You need to get the pdf and then use that to get the cdf. Then you use the cdf as an inverse lookup table to find out what gray level needs to be mapped to what gray level.

I don't think histeq() uses that method exactly. It's a variant of it but it's still bad. In general you don't want to do histogram equalization. It gives funny looking, unnatural images. You'll get more natural images using imadjust(), which uses a linear transform.