My wish is just to add a value between 1 and 100 to the compare function parameters. It represents the percentage of similitude of the images : in many cases images are not exactly the same but are ...
Montikore, cunderw I have created a feature request in the past, related to this. It can be found here.
Sometimes the images you have to compare are "equal" except they are different in size, for example a the size of a side bar is rendered differently in IE compared to FF, which results in huge amount of difference, if you check on pixel level. Because if the bar is for example 500 pixels wide, then each difference in pixel row would be a difference of 500 pixels, but you have to be able to set a tolerance on size so you can check if they are equal and accept some difference in size