User's Manual

236
ADOBE PHOTOSHOP CS2
User Guide
to surrounding pixels and diffused throughout the image, resulting in a grainy, filmlike texture. This option is useful
for viewing images on a black-and-white screen.
Halftone Screen Simulates the appearance of halftone dots in the converted image.
Custom Pattern Simulates the appearance of a custom halftone screen in the converted image.
Original grayscale image, and 50% Threshold conversion method
Pattern Dither conversion method, and Diffusion Dither conversion method
To convert a Bitmap mode image to Grayscale mode
You can convert a Bitmap mode image to Grayscale mode in order to edit it. Keep in mind that a Bitmap mode image
edited in Grayscalemodemay notlookthe same when youconvert it back to Bitmap mode.For example, supposea
pixelthatisblack in Bitmap mode is edited to ashade of gray in Grayscalemode. When theimage is convertedback
to Bitmap mode, that pixel is rendered as white if its gray value is above the middle gray value of 128.
1 Choose Image > Mode > Grayscale.
2 Enter a value between 1 and 16 for the size ratio.
The size ratio is the factor for scaling down the image. For example, to reduce a grayscale image by 50%, enter 2 for
t
he size ratio. If you enter a number greater than 1, the program averages multiple pixels in the Bitmap mode image
to produceasingle pixelinthe grayscaleimage.Thisprocess lets yougeneratemultipleshadesofgrayfromanimage
scanned on a 1-bit scanner.
Specifying the halftone screen for Bitmap mode images
The Halftone Screen option in the Bitmap dialog box lets you convert a grayscale image to simulated halftone dots.
Important: T
hehalftonescreenbecomes part of theimage.Ifyou printthe imageonahalftone printer, theprinter will
useits ownhalftonescreenaswellasthe halftone screen that is part of theimage.Onsomeprinters, theresultisamoiré
pattern.