Autotek autocad raster design 2010 ユーザーズマニュアル

Press Enter for entire image or specify sub-region option [Existing/Clip
region/Window/Polygon]:

2 Do one of the following:

■

Press Enter to use the histogram on the entire image.

■

Enter e, then click a closed vector entity to use an existing entity to
define the region.

■

Enter c to use an existing image clip.

■

Enter w, then enter two points to define a rectangular sub-region.

■

Enter p, then enter several points to define a polygonal sub-region.

 (page 316) dialog box is displayed.

3 Click the Tonal Adjustment tab.

A preview of the image is displayed. If you selected more than one image,
the histogram displays a composite of the images' values. You can view
each image by clicking its name in the list.

NOTE The preview reflects the image as it was read from the disk. If you
have made any display-only adjustments to the image using the AutoCAD
IMAGEADJUST command, then those adjustments are not displayed in the
image preview. If you make adjustments to the image using the Histogram,
the adjustments made with IMAGEADJUST are no longer applied to the image;
instead the new settings are applied.

4 If you selected a color image, then select a color channel to manipulate.

You can manipulate the contrast curve for the combined RGB channels,
or you can select a single channel (red, green, or blue).

5 Select a curve type from the Select Curve Type list:

■

Choose Gamma correction to create an exponential curve by defining
either the single exponent (gamma) value or using an interactive slider
which determines the gamma value.

■

Choose Fitted to draw a curve smoothly through points you specify
by clicking and dragging on curve segments or on existing points.

■

Choose Piecewise Linear to draw straight segments between points
you specify. You can create or modify points by clicking and dragging
on curve segments or on existing points.

Adjusting Images with the Histogram | 103