what willbe best image density matching technique

i want to compare twoimages and compare densities between two ,so what algorithm will work best even if i miss to apply image registration 1.i have a image of a empty road(reference) 2.i have a image of same densed road with vehicles(real time) 3.i want to match these two images densities(want answer in %) 4.algorithm should work for day and night.

Answer 1

[Image Analyst]

In the Image Processing Toolbox, there are functions histeq() and imhistmatch(). If you want a perfectly flat histogram, see my attached demos.

If you want a completely custom histogram of exactly the shape you define, see my File Exchange http://www.mathworks.com/matlabcentral/fileexchange/28972-custom-shaped-histogram. Note how the histogram below has the shape of the girl's silhouette.

Answer 2

[Image Analyst]

The best algorithm I've seen for color histogram matching is by Grundland and Dodgson: http://www.eyemaginary.com/Portfolio/ColorHistogramWarp.html