On 6/10/07, DJ wrote:

Hi Gimp-user,

How do I know the numeric black (darkest) and white (lightest) points of an image?

What is the easiest way to change the black and white points of a group of images?

If I look at Levels it shows 0 and 255, as the range. The histogram is, I guess, shows those points at the end, but is it numeric anywhere?

Thank you.

Levels doesn't try to be excessively smart -- when you start up it is always set to the same fixed values (which do nothing). Clicking the Auto button will autodetect the white and black points (see the Red, Green, and Blue adjusters.)
The levels tool incorporates a way to select black, grey, and white points in a similar way to eyedropping (in fact, the icons are eyedroppers.) - just click on the icon, then on the appropriate point in the image. Then you just need to set the output range to whatever range you want the black..white points to be.

On 6/10/07, David Gowers wrote:

The levels tool incorporates a way to select black, grey, and white points in

Correction -- it allows only to select black and white points, not grey