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Color specials

We will describe `background' first, since it is the simplest. The `background' keyword must be followed by a color specification. That color specification is used as a fill color for the background. The last `background' special on a page is the one that gets issued, and it gets issued at the very beginning of the page, before any text or specials are sent. (This is possible because the prescan phase of Dvips notices all of the color specials so that the appropriate information can be written out during the second phase.)

The `color' special itself has three forms. The first is just `color' followed by a color specification. In this case, the current global color is set to that color; the color stack must be empty when such a command is executed.

The second form is `color push' followed by a color specification. This saves the current color on the color stack and sets the color to be that given by the color specification. This is the most common way to set a color.

The final version of the `color' special is just `color pop', with no color specification; this says to pop the color last pushed on the color stack from the color stack and set the current color to be that color.

Dvips correctly handles these color specials across pages, even when the pages are repeated or reversed.

These color specials can be used for things such as patterns or screens as well as simple colors. However, note that in the PostScript, only one color specification can be active at a time. For instance, at the beginning of a page, only the bottommost entry on the color stack is sent; also, when a color is popped, all that is done is that the color specification from the previous stack entry is sent. No `gsave' or `grestore' is used. This means that you cannot easily mix usage of the `color' specials for screens and colors, just one or the other. This may be addressed in the future by adding support for different categories of color-like state.

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