Enhanced graphics capabilities are one of the most powerful aspects of QuickDraw GX. The QuickDraw GX graphics model revolutionizes the way the Macintosh deals with graphics. Graphics are no longer treated in the old QuickDraw sense of 72 dpi, but are instead resolution and device-independent.
An object-based system, QuickDraw GX uses shapes as the basis for everything, type included. Images are now described by geometric structures such as points, lines, and curves, instead of the old bitmap approach. The advantage of this approach is that you can modify almost anything and yet your changes are not permanent -- you are therefore free to experiment, to try new things out without fear of getting into trouble.
Working with shapes in a GX-compatible graphics program is a wonderful easy thing to do. Shapes can be created from scratch, distorted from others, or can be the result of addition or subtraction operations with other shapes.
QuickDraw GX cooperates fully with Apple's ColorSync color management technology. ColorSync, a system extension, adds new color capabilities to the Macintosh. It assures consistent color between scanners, displays, printers, and other input and output devices. Basically ColorSync assures that the colour you see on the screen is the colour you see on paper. Technically speaking, "It facilitates color conversion from the color space (method of mathematically describing a color) of one device to the color space of another device. It does this while maintaining consistent visual representation." (taken from ColorSync: Setting Up & Using ColorSync (5/95))
The QuickDraw GX graphics model includes support for things like transfer modes. These include functions like : transparency, translucency, hue, saturation, brightness, tints and masks, etc.
QuickDraw GX allows for overlapping of shapes and the colours that make them up. GX treats colours intelligently rather than as static fixed values, adding colour values together and then showing the result. It will take into consideration the sum of the colours, therefore adding together the results of the red and the blue, producing some shade of purple. With QuickDraw GX, colours interact, and even blend, just as they do in real life.
In the example above, you can see the interaction between the different colours as they overlap and the wonderful new colours that are produced by this overlapping. In order to achieve the effect that you see here in traditional graphics programs like Illustrator and Freehand, you would have to create those colours from scratch, and do alot of cutting/combining of shapes. GX actually adds the values of each of the colours that you see here and saves you alot of the work.
The PostScript system, which is based on an ink on paper model, has no easy way to treat transparency. The result is that when using a non-GX program like Adobe Illustrator, if you superimpose a blue circle over a red triangle, you'll see the part on top, followed by the part underneath, but no relationship between the two.
Transfer modes can be achieved by placing another shape over the original image and then affecting a quality to that second shape, like for example, hue or saturation. Much as in real life, if you hold a red transparency in front of your eyes, only the red colour in things will show through ; the original image is not modified, but only specific
colours will show.
Unlike in Photoshop, where once an effect like a hue or saturation is applied, the effect is permanent, in a GX-savvy graphics application, the changes are never permanent. With QuickDraw GX-savvy applications, no permanent changes to the image are needed. GX takes care of calculating the resulting colour information of the different objects on the fly.
Text as graphics
GX functionality sets GX-savvy programs apart from the others. For example, in a GX graphics-savvy program, you can extrude text directly in the program, rotate it and even slant it too. Should you decide to change the text, no problem -- you can edit it right there, whether it's on a slanted line, or with whatever effect you chose applied. (Note : The text example looks jaggy because I took a screen shot and the Macintosh screen is limited to 72dpi -- this effect prints perfectly from the application that created it with no problem)
Exporting GX graphics
Files created in GX-graphics compatible applications may also be used in other non-GX applications, without necessarily losing the special effects created by GX. A GX graphic can be exported as a PICT file. What is interesting about it is that in addition to normal Quickdraw data, the PICT file also contains Quickdraw GX data.
In effect, the PICT file, while looking like and behaving like a regular PICT file, actually contains special hints in a resource (QDGX) within itself. A GX-enhanced PICT file differs from a regular PICT file in that it is resolution independent -- you are no longer limited to just 72 dpi -- as long as QuickDraw GX is installed. If you place the PICT in a non-GX app you will discover that it can be zoomed, re-sized, printed at hi-res, etc., again provided you have GX installed.