How to test for pixel density in an image

I have an image where at each point pixel density varies. I need to identify low pixel density regions in image and differentiate it from high density image.Any help would be highly appreciated.

[Walter Roberson]

Are you sure that the sensor was non-linear? How do you display the image? Do you have to texture map it onto a surface?

"pixel density" refers to the individual locations that are given values. If you are not working with "raw" images, then pixels are almost always arranged on a rectangular grid, and so the "pixel density" is uniform.

Perhaps you should post a sample image.

[Image Analyst]

What do you mean by pixel density? That is non-standard terminology because it is not specific. Sometimes people (or programs like Photoshop) talk about density and they mean "optical density" (holdover terminology from the old film days), which is essentially gray level. Or you might mean how many pixels are packed into a certain size sensor, like there are 15 or 18 megapixels in this APS-C format sensor. What do you mean?