Threshold

The Threshold command (in the Adjust section of the Image menu) converts all the colors in an image to just two: black and white. The threshold is a limit value above which tones become black and below which they become white. Therefore you can decide how much of the image becomes black and how much white.

image\ppThresholdDlg.gif

In the "Threshold" dialog use the slider to set a threshold value anywhere between 0 and 255. Towards the upper end of the scale the image becomes darker and is completely black at 255; towards the lower end the image becomes lighter and is completely white at 0. The current threshold is displayed numerically in the Threshold Level box. The default threshold is 127 when you first enter the dialog i.e. half way between black and white.

The histogram represents the distribution of image tones and can be used as a rough guide to help you set the threshold.

The command is immediately applied when you enter the dialog, initially using the 127 default threshold value and then any other value you may set with the slider. To cancel these changes and return to the original image click on Cancel, otherwise click on OK to exit the dialog and keep the changes.

Once you have applied the Threshold command you can only get back to the original colored image by selecting Undo Threshold from the Edit menu.

See:

Adjust Image