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This section describes the features of the Image Colors Editor and also includes a module containing details on how to use the Color Editor.

Note: The controls in the upper color portion of the dialog box are mirrored in the lower color portion. The controls in both portions behave the same way.

Use Color Model

Red, Green, Blue (RGB) and Hue, Saturation, and Brightness (HSB) Check Buttons allow you to choose the color model.

HSB/RGB Slider Bars

These slider bars allow you to make incremental changes in the components of the color displayed in the Color Swatch. These values can be set using the slider bar or by typing a value in the entry box to the right of the slider.

• Hue: Values for hue range from 0-359 and determine the amount of color tint. Changing hue values moves the Color Wheel Centroid around the circumference of the Color Wheel. Try dragging the Hue Slider Bar (to change the hue value) and notice the movement of the Centroid.

• Saturation: Saturation values are given in percent (0-100) and determine the amount of white (the higher the value, the less white) present in the color. Changing saturation values moves the Color Wheel Centroid along a radial of the Color Wheel. Change the saturation values and note the movement of the Centroid.

• Brightness: As with saturation, brightness values are also given in percent (0-100). Brightness determines the amount of black present in the color. The higher the values, the less black present. Brightness can also be thought of as the intensity of the color.

• Red, Green, Blue: The red, green, and blue values in the RGB mode all range from 0-255 and reflect the amount, or intensity, of each color present in the displayed color. Changing these values moves the Color Wheel Centroid across the Color Wheel, but not necessarily along a radial.

• Color Wheel: The box on the right side of the dialog box contains the Color Wheel. When the editor is in its default mode, the top Color Wheel has both the saturation and brightness values set to zero. Consequently the Color Wheel is black. Increasing the brightness value makes the wheel visible.

The Color Wheel Centroid (a circle with a dot in the middle) can be dragged anywhere within the circle to change the color displayed in the Color Swatch (more on this later in this section). Moving the Centroid around the circle also changes the HSB or RGB values. In HSB mode, brightness cannot be changed by dragging the Centroid.

• Color Swatch: Below and to the far right of the Use HSB/Use RGB Check Button is the Color Swatch. Moving the Color Wheel Centroid changes the color in the swatch. Also, clicking anywhere in the top half of the Color Bar (located in the middle of the dialog box), fills the top Color Swatch with the corresponding color; clicking anywhere in the lower half of the Color Bar fills the bottom Color Swatch.

• Set: These buttons, located in both the upper and lower portions of the Image Colors Editor, insert a narrow line of color into the current Color Bar at the location of the Color Pointer. The color inserted is the one displayed in the corresponding (i.e., upper or lower) Color Swatch.

• Fill: These buttons replace the colors contained within the range specified by the Color Pointers in the Color Bar with the colors in the upper or lower Color Swatch.

• Color Bar: The Color Bar contains the color table of the current image and is located in the middle of the dialog box.

The arrowhead Color Pointers along the top and bottom halves of the Color Bar can be dragged to delineate a range of the color table; that is, the portion of the Color Bar contained between the top and bottom arrows. The Color Pointers move independently of one another, but they cannot move past each other. When aligned, they move in unison and delineate a single point along the Color Bar.

As the Color Pointers are dragged along the Color Bar, they display the image values corresponding to the color pointed to. Thus, for example, if an infrared satellite image is displayed, moving the Color Pointer shows the temperature values corresponding to the colors in the Color Bar.

Note: As the Color Pointers are moved, they are filled with the color they are pointing to.

To either side of the Color Bar are left- and right-pointing arrows. These are used to move the Color Pointers along the Color Bar an increment at a time. The > and < move one image value at a time (i.e., 256 steps through the color bar), while >> and << move one color band at a time. In the case illustrated, there is no difference in behavior between the two. For a radar color table, the << moves to the next of the 16 colors.

• Edit Controls: At the bottom of the dialog box are the Edit Controls.

- Interpolate: This button fills the specified range of values with intermediate colors. In both RGB and HSB modes, each component is interpolated. For RGB, the effect is more or less one of moving across the color wheel in a straight line from the upper color to the lower; while in HSB, the centroid motion is along an arc or spiral. (In fact, the RGB interpolation is not necessarily a straight line across the color wheel, as one can see from the example in Objective 2 of Module 5 in the next section.)

A linear interpolation is equivalent to moving in a straight line across the Color Wheel.

A nonlinear interpolation is equivalent to moving around the Color Wheel.

- Undo: This button allows you to successively undo changes made to the color table.

- Redo: This button successively redoes the last edit that was undone.

- Revert: This button returns the Color Bar (and the displayed image) to its original state.

- Save: This button saves changes that you have made to a color table. If you are editing a read-only color table, or one that is owned by another user, this menu button is disabled.

- Save As...: A menu button that opens the Save As Dialog Box in which you can enter a name for your color table. The color table is saved in a file containing the customized color tables for the current user. If the new name of the color table is the same as a name of an existing color table in this file, a dialog box opens and asks you if you want to overwrite the existing color table.

- Office Save As...: With this menu button, you can save a newly edited color table so that it is accessible on every workstation in your office. A dialog box asks you to enter a name for your color table and then lets you save it or cancel the command.

- Delete...: This button allows you to delete an edited color table. A confirmation dialog box opens to confirm your request. This menu button is disabled if you are editing a read-only color table or a color table that is owned by another user.

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