CGFunction Reference

Overview

The CGFunctionRef opaque type provides a general facility for defining and using callback functions. These functions can take an arbitrary number of floating-point input values and pass back an arbitrary number of floating-point output values.

Quartz uses CGFunction objects to implement shadings. CGShading Reference describes the parameters and semantics required for the callbacks used by CGFunction objects.

Functions by Task

Creating a CGFunction Object

• CGFunctionCreate

Retaining and Releasing CGFunction Objects

• CGFunctionRelease
• CGFunctionRetain

Getting the CFType ID

• CGFunctionGetTypeID

Functions

CGFunctionCreate

Creates a Quartz function.

CGFunctionRef CGFunctionCreate (
   void *info,
   size_t domainDimension,
   const CGFloat *domain,
   size_t rangeDimension,
   const CGFloat *range,
   const CGFunctionCallbacks *callbacks
);

CGFunctionGetTypeID

Returns the type identifier for Quartz function objects.

CFTypeID CGFunctionGetTypeID (
   void
);

CGFunctionRelease

Decrements the retain count of a function object.

void CGFunctionRelease (
   CGFunctionRef function
);

CGFunctionRetain

Increments the retain count of a function object.

CGFunctionRef CGFunctionRetain (
   CGFunctionRef function
);

Callbacks

CGFunctionEvaluateCallback

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

typedef void (*CGFunctionEvaluateCallback) (
   void *info,
   const float *inData,
   float *outData
);
   

If you name your function MyCGFunctionEvaluate, you would declare it like this:

void MyCGFunctionEvaluate (
   void *info,
   const float *inData,
   float *outData
);

void evaluateSquare(void *info, const float *inData, float *outData)

{

    outData[0] = inData[0] * inData[0];

}

CGFunctionReleaseInfoCallback

Performs custom clean-up tasks when Quartz deallocates a CGFunction object.

typedef void (*CGFunctionReleaseInfoCallback) (
   void *info
);
   

If you name your function MyCGFunctionReleaseInfo, you would declare it like this:

void MyCGFunctionReleaseInfo (
   void *info
);

Data Types

CGFunctionRef

An opaque type that represents a callback function.

typedef struct CGFunction *CGFunctionRef;

CGFunctionCallbacks

A structure that contains callbacks needed by a CGFunction object.

struct CGFunctionCallbacks
{
unsigned int version;
CGFunctionEvaluateCallback evaluate;
CGFunctionReleaseInfoCallback releaseInfo
};

typedef struct CGFunctionCallbacks CGFunctionCallbacks;

Fields

version

The structure version number. For this structure, the version should be 0.

evaluate

The callback that evaluates the function.

releaseInfo

If non-NULL, the callback used to release the info parameter passed to CGFunctionCreate.