User Guide

CHAPTER 4
70
Choosing a Color Mode
The following mode conversions flatten the file:
• RGB to Indexed color or Multichannel mode.
• CMYK to Multichannel mode.
• Lab to Multichannel, Bitmap, or Grayscale
mode.
• Grayscale to Bitmap, Indexed, or Multichannel
mode.
• Duotone to Bitmap, Indexed, or Multichannel
mode.
Converting between Grayscale
mode and Bitmap mode
Converting an image to Bitmap mode reduces the
image to two colors, greatly simplifying the color
information in the image and reducing its file size.
To convert an image to Bitmap mode, you must
first convert it to Grayscale mode. This removes
the hue and saturation information from the
pixels and leaves just the brightness values.
However, because few editing options are available
for Bitmap-mode images, it’s usually best to edit
the image in Grayscale mode and then convert it.
Keep in mind that a Bitmap-mode image edited in
Grayscale mode may not look the same when
converted back to Bitmap mode. For example, a
pixel that is black in Bitmap mode and then edited
in Grayscale mode may be converted to a shade of
gray. If the pixel is light enough, it will be white
when converted back to Bitmap mode.
To convert an image to Bitmap mode:
1 Do one of the following:
• If the image is in color, choose Image > Mode >
Grayscale. Then choose Image > Mode > Bitmap.
• If the image is grayscale, choose Image > Mode >
Bitmap.
2 For Output, enter a value for the output
resolution of the Bitmap-mode image, and choose
a unit of measurement. By default, the current
image resolution appears as both the input and the
output resolutions.
3 Select a bitmap conversion method, and click
OK. If you choose Halftone Screen, see the
following section. For other conversion methods,
see “Additional bitmap conversion options” on
page 71.
To convert a Bitmap-mode image to grayscale:
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 the size ratio. If you enter a
number greater than 1, the program averages
multiple pixels in the Bitmap-mode image to
produce a single pixel in the grayscale image. This
process lets you generate multiple shades of gray
from an image scanned on a 1-bit scanner.