[user guide] Image comparison

Fresco offers several difference measures. Different modalities can be compared (underdrawings, changes of composition) as near infra red images or ultra-violet fluorescence as well as different "simliar" images. These measures are useful for comparison of forgeries or copies.

How to use this function:

• open two similar image
• register them according to user guide - Registration
• open them as inputs (single click for first one in image toolbar and ctrl+single click for second image)
• Select difference measure ** Analysis -> Colour blending offer colour selection. Result image has first colour in places where first image is brighter than second, gray colour in places where brightness of both images is similar and second colour in places where second image is brighter than first image. ** Analysis -> Image difference - white parts of result image shows places with big absolute difference (brightness of both images is normalised), dark parts are similar.

Video tutorial: Fresco - image comparison