Changing Colors, Contrast, and Intensity

The graphics object bar (Figure 31-1) is only available when you select a raster object. It allows you to change color saturation, etc. If it isn't displayed, choose View > Toolbars > Object Bar.

Figure 31-1. Graphics object bar available when raster object is selected

graphics/31fig01.jpg

Note

The gamma value is a measurement unit used for contrasting gray tones.


Editing RGB Color Values

You can increase or decrease the red, green, or blue in an image just by entering different numbers or clicking the arrows, in the image-editing toolbar.

graphics/31inf01.jpg

To make the toolbar appear, click on the image. Make the adjustments you want by entering a number or clicking the up and down arrows.

Changing Color Resolution

You can reduce the number of colors in a bitmap to optimize it for Web use, for instance. Examples are shown in Figure 31-2.

Figure 31-2. Examples of different color resolutions

graphics/31fig02.jpg

To change the resolution, right-click the object and select the appropriate color resolution, as shown in Figure 31-3. You can change the resolution of only one object at a time; if you select two or more objects, the Color Resolution item won't appear.

Figure 31-3. Changing color resolution

graphics/31fig03.jpg

Changing Selected Colors in Images Using the Eyedropper

One of the most powerful features of Image is the eyedropper. You can use the eyedropper tool to sample change a color to a different color everywhere it appears in your image.

You may get unexpected results; one of the colors you select to be changed might show up in your graphic where you don't expect it. Carefully check the results you get, and be prepared to use the Undo feature.

  1. Choose Tools > Eyedropper, to display the Eyedropper window (Figure 31-4).

    Figure 31-4. Using the Eyedropper

    graphics/31fig04.jpg

    If you want to simply replace a transparent value with a color, select the Transparency option and select a color. You can replace colors or transparency, but not both.

  2. In the Eyedropper window, click the eyedropper icon in the upper left corner.

  3. Move the mouse to the first color in the drawing area that you want to replace. You can see the color you're over in the color field in the Eyedropper window. When you see the color you want in that field, click the mouse.

    Note

    If the mouse pointer turns to the "Ghostbusters" symbol, just click in the Eyedropper window and it'll return to normal.

  4. Enter the tolerancehow exact the color match should be. Start with the default, 10%, but you'll probably need to increase it to 30% or 50%.

  5. In the Replace with list, select the color to change to.

  6. To select other colors to change, select the checkbox next to the second of the four color fields. Repeat steps 25.

  7. Click Replace. If nothing happens, increase the tolerance and click Replace again.

Editing Contrast and Transparency

The image editing toolbar also lets you change the following values:

graphics/31inf02.jpg

  • Brightness Values between 100% (only black) and 100% (only white).

  • Contrast Values between -100% (no contrast at all) to +100% (full contrast).

  • Gamma Values from .01 (minimum) to 10 (maximum).

  • Transparency Values from 0 to 100%.

To make the toolbar appear, click on the image. Make the adjustments you want by entering a number or clicking the up and down arrows.



OpenOffice. org 1.0 Resource Kit
OpenOffice.Org 1.0 Resource Kit
ISBN: 0131407457
EAN: 2147483647
Year: 2005
Pages: 407

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