Consolidating colors
The Threshold and Posterize commands let you consolidate color
values in an image or selection. Besides producing interesting effects
with these commands, you can use them in alpha channels to help
isolate areas within an image.
If you select an area within an image, Canvas applies the adjustment
only to that area. Otherwise, Canvas adjusts the selected paint
objects.
Setting a brightness threshold
You can use the Threshold command to convert any image to black
and white. The Threshold command compares each pixels bright-
ness value to a threshold value that you set. It changes brighter pixels
to white and darker pixels to black. The threshold setting is based on
a scale of brightness values from 0 (black) to 255 (white). You cant
use the Threshold command on images in Black & White or Indexed
mode.
For example, if you set a threshold value of 128, pixels that are
brighter than medium gray become white, while pixels darker than
medium gray become black.
To map an image to black and white
1
Select one or more paint objects to adjust all the images. You
can select an area in one image in edit mode to adjust the selected
area only. If you dont make a selection, the entire image is
affected.
2
Choose Image > Adjust > Threshold.
3
In the Threshold dialog box, enter the threshold value by drag-
ging the slider or typing a number in the text box. If you want Can-
vas to convert half the pixels to black and half to white, click Auto.
4
After entering the setting you want, click OK.
To isolate selections, you can apply the Threshold command in con-
junction with the High Pass filter to an image in an alpha channel.
See Isolating areas using the High Pass filter on page 35.720.