High Contrast

This command lets you create a high contrast black and white version of the input image. It works by comparing the brightness of each pixel in the input image to a threshold value. Where the pixels are brighter than the threshold, the output image is white; where they are darker, the output image is black. Output pixels that lie on the boundary between black and white areas, are set to an appropriate gray level to make the boundary appear smooth.

You can use the Tint transformation to colorize the output image if you want some color scheme other than black and white.

This transformation is similar to using the Brightness Curve transformation, except that it handles the boundary between black and white areas in the output image more accurately.

Amount

This control lets you control how much of the high contrast transformation is applied to the input image. You can apply a percentage of the transformation to the entire image, or you can specify an amount mask to restrict the effects of the transformation to only part of the input image.

Threshold Amount

The threshold amount control lets you control what gray level the input image is tested against to decide if the output image is black or white. You can use the same threshold value for the entire image, or you can specify a mask to use different thresholds over different parts of the image.