QuartzComposer is a free application that is bundled with Apple’s latest developer tools since Tiger.

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This app lets you build “qtz” files graphically by dragging Quartz filters and other graphic components called “patches” onto a schematic like working surface. Components are connected together by dragging lines between each component’s input and output ports. Search ADC with the key words “Quartz” and “Composer” for more info.

http://developer.apple.com/documentation/GraphicsImaging/Conceptual/QuartzComposer/qc_intro/chapter_1_section_1.html