Inside Macintosh: Imaging With QuickDraw /

Chapter 1 - Introduction to QuickDraw

Other Graphics Managers

In addition to the QuickDraw routines described in this book, several other collections of system software routines are available to assist you in drawing and printing images.

Your application can use QuickDraw's text-handling routines to measure and draw text ranging in complexity from a single glyph to a line of justified text containing multiple languages and styles. In addition to measuring and drawing text, QuickDraw's text-handling routines also help you to determine which characters to highlight and where to mark the insertion point. These routines are described in the chapter "QuickDraw Text" in Inside Macintosh: Text.

To provide more sophisticated color support on indexed graphics devices, your application can use the Palette Manager. The Palette Manager allows your application to specify sets of colors that it needs on a window-by-window basis. An indexed device supporting a byte for each pixel allows 256 colors to be displayed. On a video device that uses a variable CLUT, your application can use the Palette Manager to display tens of thousands of palettes--that is, sets of colors--consisting of 256 colors each, so that your application has up to 16 million colors at its disposal (although only 256 different colors can appear at once). For example, your application can use the Palette Manager to load the CLUT with a set of prevailingly brown colors to display a Rembrandt painting, then reload the CLUT with a set of prevailingly blue colors for a Monet painting. For information about the Palette Manager, see Advanced Color Imaging on the Mac OS.

To solicit color choices from users, your application can use the Color Picker Utilities. The Color Picker Utilities provide your application with a standard dialog box for soliciting a color choice from users. The Color Picker Utilities also provide routines that allow your application to convert between colors specified in RGBColor records and colors specified for other color models, such as the CMYK model used by many color printers. Most applications use the Color Picker Utilities only for soliciting color choices. To learn how to use the Color Picker Utilities, see Advanced Color Imaging on the Mac OS.

As color devices for input and output proliferate, so do the problems of moving images between them with good results. Different device types use different color models, which produce different gamuts, or ranges of colors. Screens, for example, typically display colors as combinations of red, green, and blue--combinations that your application specifies with RGBColor records when using Color QuickDraw. Screens by different manufacturers may be capable of displaying different intensities of red, green and blue, so that even though the screens work with RGB colors, their gamuts may be different. Color printers typically use a CMYK color model to work with varying intensities of cyan, magenta, yellow, and black. Print technologies vary drastically, and the gamut that an ink jet color printer can display may be quite different from one based on another technology. A single printer may be able to produce different gamuts depending on the paper or ink in use at the time of printing.

Two devices with differing color gamuts cannot reproduce each other's colors exactly, but shifting the colors of one device may improve the visual match. To match colors between screens and input and output devices such as scanners and printers, Macintosh system software provides a set of routines and algorithms called the ColorSync Utilities. Developers writing device drivers use the ColorSync Utilities to support color matching between devices. You can use the ColorSync Utilities in your application to communicate with a driver and present users with color-matching information--such as a device's color capabilities. For an image that your application prepares, for example, your application can present a print preview dialog box that signifies those colors within the image that the printer cannot accurately reproduce. Your application can also allow users to choose whether and how to match colors in the image with those available on the printer. The ColorSync Utilities are described in Advanced Color Imaging on the Mac OS.

The Color Manager assists Color QuickDraw in mapping your application's color requests to the actual colors available. Most applications never need to call the Color Manager directly. However, for completeness, the routines and data structures of the Color Manager are described in Advanced Color Imaging on the Mac OS.

Apple has also developed a new, object-based graphics architecture called QuickDraw GX. This new architecture provides applications with sophisticated color publishing capabilities. Your application can use QuickDraw GX instead of QuickDraw to create and draw objects on the screen. Rather than provide a set of drawing commands, as QuickDraw does, QuickDraw GX is built around graphics objects that your application can use as needed.

Your application can also use QuickDraw GX for drawing text. QuickDraw GX provides many sophisticated font and line layout capabilities, such as ligatures, style variations, kerning, and resolution-independent type manipulation.

For printing, QuickDraw GX offers flexible new capabilities to users and an architecture that streamlines development time for developers who write printing drivers. Even if your application uses QuickDraw and the Font Manager instead of QuickDraw GX to create images and text, your application can use the printing capabilities of QuickDraw GX.

See the Inside Macintosh: QuickDraw GX suite of books for information about programming with QuickDraw GX imaging technology.