Adobe PHOTOSHOP ELEMENTS Manual page 78

CHAPTER 3
70
Working with Color
To convert an image to another mode:
Choose Image > Mode, and choose the mode you
want from the submenu. Modes not available for
the active image appear dimmed in the menu.
Note: Images are flattened when you convert them to
Bitmap or Indexed Color mode, because these modes
do not support layers.
Converting between Grayscale and
Bitmap modes
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,
consider a pixel that is black in Bitmap mode and
then edited to a shade of gray in Grayscale mode.
If the gray value of the pixel is light enough, it
will become white when converted back to
Bitmap mode.
To convert an image to Bitmap mode:
Do one of the following:
1
If the image is in color, choose Image > Mode >
•
Grayscale. Then choose Image > Mode > Bitmap.
If the image is grayscale, choose Image > Mode >
•
Bitmap.
For Output, enter a value for the output
2
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.
Select one of the following bitmap conversion
3
methods, and click OK:
Converts pixels with gray values
50% Threshold
above the middle gray level (128) to white and
below to black. The result is a very high-contrast,
black-and-white representation of the image.
Converts an image by organizing
Pattern Dither
the gray levels into geometric configurations of
black and white dots.
Converts an image by using an
Diffusion Dither
error-diffusion process, starting at the pixel in the
upper left corner of the image. If the pixel's value
is above middle gray (128), the pixel is changed
to white—if below, to black. Because the original
pixel is rarely pure white or pure black, error is
inevitably introduced. This error is transferred to