CGFunction

A general facility for defining and using callback functions.

Overview

These functions can take an arbitrary number of floating-point input values and pass back an arbitrary number of floating-point output values.

Core Graphics uses CGFunctionRef objects to implement shadings. CGShading describes the parameters and semantics required for the callbacks used by CGFunctionRef objects.

Topics

Creating a CGFunction Object

CGFunctionCreate

Creates a Core Graphics function.

Retaining and Releasing CGFunction Objects

CGFunctionRelease

Decrements the retain count of a function object.

CGFunctionRetain

Increments the retain count of a function object.

Getting the CFType ID

CGFunctionGetTypeID

Returns the type identifier for Core Graphics function objects.

Callbacks

CGFunctionEvaluateCallback

Performs custom operations on the supplied input data to produce output data.

CGFunctionReleaseInfoCallback

Performs custom clean-up tasks when Core Graphics deallocates a CGFunctionRef object.

Data Types

CGFunctionRef

A general facility for defining and using callback functions.

CGFunctionCallbacks

A structure that contains callbacks needed by a CGFunctionRef object.

See Also

Opaque Types

CGBitmapContext

A type of CGContextRef that you can use for drawing bits to memory.

CGColor

A set of components that define a color, with a color space specifying how to interpret them.

CGColorConversionInfo

An object that describes how to convert between color spaces for use by other system services.

CGColorSpace

A profile that specifies how to interpret a color value for display.

CGContext

A Quartz 2D drawing destination.

CGDataConsumer

An abstraction for data-writing tasks that eliminates the need to manage a raw memory buffer.

CGDataProvider

An abstraction for data-reading tasks that eliminates the need to manage a raw memory buffer.

CGFont

A set of character glyphs and layout information for drawing text.

CGGLContext

Deprecated. A type of CGContextRef for drawing OpenGL content.

CGGradient

A definition for a smooth transition between colors for drawing radial and axial gradient fills.

CGImage

A bitmap image or image mask.

CGLayer

An offscreen context for reusing content drawn with Core Graphics.

CGPath

Immutable and mutable types for graphics paths: mathematical descriptions of shapes or lines to be drawn in a graphics context.

CGPattern

A 2D pattern to be used for drawing graphics paths.

CGPDFArray

An array structure within a PDF document.

CGPDFContentStream

A representation of one or more content data streams in a PDF page.

CGPDFContext

A type of CGContextRef for drawing PDF content.

CGPDFDictionary

A dictionary structure within a PDF document.

CGPDFDocument

A document that contains PDF (Portable Document Format) drawing information.

CGPDFObject

An object representing content within a PDF document.

CGPDFOperatorTable

A set of callback functions for operators used when scanning content in a PDF document.

CGPDFPage

A page in a PDF document.

CGPDFScanner

A parser object for handling content and operators in a PDF content stream.

CGPDFStream

A stream or sequence of data bytes in a PDF document.

CGPDFString

A text string in a PDF document.

CGPSConverter

An object that converts PostScript data to PDF data.

CGShading

A definition for a smooth transition between colors, controlled by a custom function you provide, for drawing radial and axial gradient fills.