I would like to measure the quality of a color image, possibly as a difference to another image, but if possible, on its own too.
This question comes from the fact that we have a vision application, and improve lighting conditions, calbirations, and similar surrounding conditions. We want to measure the improvement of the quality of the image, such as:
- Amount of detail
- Other things that describe the quality of an image or the amount of information in an image
Do you have ideas for this? Maybe histogram comparisons, or an advanced distance measure on the histogram? I'd love to hear some good ideas!
Of course the results of the vision application are a measure of the quality of the images. But:
- it is not intended as a measurement for the quality, it is a measurement of something else
- there are more parameters that influence the results of the application (for example the image itself), therefore it is only a rough measure of the quality of the image
I could use human evaluation, but I really want an objective measure, especially because the human eyes are not objective (our mind plays tricks, the monitor we watch it on influences the image, etc.).
After a discussion about what quality in an image is, I'll leave this question as is. My own ideas (and of my coworkers) are the following:
- The range of the RGB channels (is it using all the colors possible)
- The mean of the Sobel amplitude (the amount of detail or a rough measure of focus, also see this question about detail)
- The amount of pixels that are clipped or 0 (no information in these pixels)
- Also the mean of the RGB channels and the YCbCr channels (after conversion), to be able to see if the average color has changed (may lead to investigating light from other sources, or after changing our own lighting)
By combining these statistics we can get an impression of the quality from a more objective point of view, instead of just looking at the images. It also leads to pointers where the changes might come from.