Adobe 29180155 - Photoshop Elements 4.0 Tutorial page 405

changes.
Note: Hidden layers are discarded and images are flattened automatically when you convert them into bitmap or indexed-
color mode, because these modes do not support layers.
RGB Color mode The default mode of new Photoshop Elements images and images from your digital camera. In RGB mode, the red, green, and
blue components are each assigned an intensity value for every pixel—ranging from 0 (black) to 255 (white). For example, a bright red color might
have an R value of 246, a G value of 20, and a B value of 50. When the values of all three components are equal, the result is a shade of neutral
gray. When the value of all components is 255, the result is pure white; when the value is 0, the result is pure black.
Convert an image to bitmap mode
To convert an image to bitmap mode, you must first convert it to grayscale mode, simplifying the color information in the image and reducing its file
size. Converting to grayscale 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.
1. Choose Image > Mode > Bitmap.
2. If the image is RGB, click OK to convert it to grayscale.
3. 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.
4. Select one of the following bitmap conversion methods, and click OK:
50% Threshold Converts pixels with gray values above the middle gray level (128) to white, and those below to black. The
result is a very high-contrast, black-and-white representation of the image.
Original grayscale image (left) and 50% Threshold conversion method applied (right).
Pattern Dither Converts an image by organizing the gray levels into geometric configurations of black and white dots.
Diffusion Dither Converts an image by using an 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 it's below middle gray, it's changed to
black. Because the original pixel is rarely pure white or pure black, error is inevitably introduced. This error is transferred to
surrounding pixels and diffused throughout the image, resulting in a grainy, film-like texture. This option is useful for viewing
images on a black-and-white screen.
Pattern Dither and Diffusion Dither conversion methods
Convert a bitmap-mode image to grayscale
Before converting, 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.
1. Choose Image > Mode > Grayscale.
2. Enter a value from 1 to 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.
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