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 pixel’s 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 can’t 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 don’t 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.
Canvas 8 Help: Image adjustment and correction (3 of 24)                                            Page #685