Autotek autocad raster design 2010 用户手册
6 Click Close to exit the Histogram dialog box.
If you are not satisfied with the results, you can use the AutoCAD UNDO
command to restore the image to the original settings.
command to restore the image to the original settings.
NOTE When you use the Threshold command on a color image, Raster Design
first converts the image to grayscale, and then uses the grayscale value to create
the bitonal image. This grayscale value is obtained by adding the values of the
red, green, and blue channels in an image and dividing the value by three. If you
want to have more control over which grayscale value Raster Design uses to create
the grayscale, then you can convert the color image to grayscale first, and then
use the Threshold command on the grayscale image. For more information, see
first converts the image to grayscale, and then uses the grayscale value to create
the bitonal image. This grayscale value is obtained by adding the values of the
red, green, and blue channels in an image and dividing the value by three. If you
want to have more control over which grayscale value Raster Design uses to create
the grayscale, then you can convert the color image to grayscale first, and then
use the Threshold command on the grayscale image. For more information, see
(page 98).
Quick Reference
Menu
Image ➤ Image Processing ➤ Histogram
Raster Design Toolbar
Command Line
ihistogram
Dialog Box
(page 316)
Making Tonal Adjustments to an Image
You can adjust the contrast selectively along the spectrum of dark and light
shades.
shades.
Many digital images, particularly those produced on a scanner, display less
detail in darker or shadowed regions of the image. Adjusting brightness and
contrast for the entire image can improve the level of detail in the darker
regions, but usually does so at the expense of the midtones and lighter colors.
Controls on the Tonal Adjustment tab of the Histogram dialog box can adjust
the contrast more selectively. You can, for example, increase the contrast in
the darker tones, while maintaining the current level of contrast among
midtones and lighter colors.
detail in darker or shadowed regions of the image. Adjusting brightness and
contrast for the entire image can improve the level of detail in the darker
regions, but usually does so at the expense of the midtones and lighter colors.
Controls on the Tonal Adjustment tab of the Histogram dialog box can adjust
the contrast more selectively. You can, for example, increase the contrast in
the darker tones, while maintaining the current level of contrast among
midtones and lighter colors.
Adjusting Images with the Histogram | 101