Legacy ImageMagick Discussions Archive

A short query.

Having applied -evaluate min=% and -evaluate max=%

where % = a chosen value

Is quantum range restored to the image automatically with the new values applied or is it necessary to normalize or auto-level the image.

I may be missing a salient point about IM operation.

I do not think the image will be automatically stretched to full dynamic range by using -evaluate min or max. It just sets the upper/lower bound.

-auto-level might be necessary then.

Shows that the maximum value will be 50% gray and minimum value is 0. So it just clips at that value and does not stretch again to full dynamic range.

If you want it stretched, use -level or -contrast-stretch or add -auto-level after -evaluate

Thanks Fred. That's what I thought. Saved me a lot of playing around.

wrote:Is quantum range restored to the image automatically with the new values applied or is it necessary to normalize or auto-level the image.

IM operations don't auto-level. If you want this, you need to explicitly ask for it.