| Inherits from | |
| Conforms to | |
| Framework | Library/Frameworks/QuartzCore.framework |
| Availability | Mac OS X v10.4 and later |
| Declared in | CIContext.h |
| Companion guides | |
| Related sample code |
The CIContext class provides an evaluation context for rendering a CIImage object through Quartz 2D or OpenGL. You use CIContext objects in conjunction with other Core Image classes, such as CIFilter, CIImage, and CIColor, to take advantage of the built-in Core Image filters when processing images.
+ contextWithCGContext:options:
+ contextWithCGLContext:pixelFormat:options: Deprecated in Mac OS X v10.6
– createCGImage:fromRect:
– createCGImage:fromRect:format:colorSpace:
– createCGLayerWithSize:info:
– drawImage:atPoint:fromRect:
– drawImage:inRect:fromRect:
– render:toBitmap:rowBytes:bounds:format:colorSpace:
Creates a Core Image context from a Quartz context, using the specified options.
+ (CIContext *)contextWithCGContext:(CGContextRef)ctx options:(NSDictionary *)dict
A Quartz graphics context (CGContextRef object) either obtained from the system or created using a Quartz function such as CGBitmapContextCreate. See Quartz 2D Programming Guide for information on creating Quartz graphics contexts.
A dictionary that contains color space information. You can provide the keys kCIContextOutputColorSpace or kCIContextWorkingColorSpace along with a CGColorSpaceRefobject for each color space.
After calling this method, Core Image draws content to the specified Quartz graphics context.
When you create a CIContext object using a Quartz graphics context, any transformations that are already set on the Quartz graphics context affect drawing to that context.
CIContext.hFrees any cached data, such as temporary images, associated with the context and runs the garbage collector.
- (void)clearCaches
You can use this method to remove textures from the texture cache that reference deleted images.
CIContext.hCreates a Quartz 2D image from a region of a CIImage object.
- (CGImageRef)createCGImage:(CIImage *)im fromRect:(CGRect)r
A CIImage object.
The region of the image to render.
A Quartz 2D (CGImageRef) image. You are responsible for releasing the returned image when you no longer need it.
Renders a region of an image into a temporary buffer using the context, then creates and returns a Quartz 2D image with the results.
CIContext.hCreates a Quartz 2D image from a region of a CIImage object.
- (CGImageRef)createCGImage:(CIImage *)im fromRect:(CGRect)r format:(CIFormat)f colorSpace:(CGColorSpaceRef)cs
A CIImage object.
The region of the image to render.
The format of the image.
The color space of the image.
A Quartz 2D (CGImageRef) image. You are responsible for releasing the returned image when you no longer need it.
Renders a region of an image into a temporary buffer using the context, then creates and returns a Quartz 2D image with the results.
CIContext.hCreates a CGLayer object from the provided parameters.
- (CGLayerRef)createCGLayerWithSize:(CGSize)size info:(CFDictionaryRef)d
The size, in default user space units, of the layer relative to the graphics context.
A dictionary, which is passed to CGLayerCreateWithContext as the auxiliaryInfo parameter. Pass NULL as this parameter is reserved for future use.
A CGLayer (CGLayerRef) object.
After calling this method, Core Image draws content into the CGLayer object. Core Image creates a CGLayer object by calling the Quartz 2D function CGLayerCreateWithContext, whose prototype is:
CGLayerRef CGLayerCreateWithContext ( |
CGContextRef context, |
CGSize size, |
CFDictionaryRef auxiliaryInfo |
); |
Core Image passes the CIContext object as the context parameter, the size as the size parameter, and the dictionary as the auxiliaryInfo parameter. For more information on CGLayer objects, see Quartz 2D Programming Guide and CGLayer Reference.
CIContext.hRenders a region of an image to a point in the context destination.
- (void)drawImage:(CIImage *)im atPoint:(CGPoint)p fromRect:(CGRect)src
A CIImage object.
The point in the context destination to draw to.
The region of the image to draw.
You can call this method to force evaluation of the result after you apply a filter using one of the methods of the CIFilter class, such as apply:, apply:arguments:options:, and apply:k, . . ..
CIContext.hRenders a region of an image to a rectangle in the context destination.
- (void)drawImage:(CIImage *)im inRect:(CGRect)dest fromRect:(CGRect)src
A CIImage object.
The rectangle in the context destination to draw into.
The subregion of the image that you want to draw into the context, with the origin and target size defined by the dest parameter.
You can call this method to force evaluation of the result after you you apply a filter using one of the methods of the CIFilter class, such as apply:, apply:arguments:options:, and apply:k, . . ..
CIContext.hRuns the garbage collector to reclaim any resources that the context no longer requires.
- (void)reclaimResources
The system calls this method automatically after every rendering operation. You can use this method to remove textures from the texture cache that reference deleted images.
CIContext.hRenders to the given bitmap.
- (void)render:(CIImage *)im toBitmap:(void *)data rowBytes:(ptrdiff_t)rb bounds:(CGRect)r format:(CIFormat)f colorSpace:(CGColorSpaceRef)cs
A CIImage object.
Storage for the bitmap data.
The bytes per row.
The bounds of the bitmap data.
The format of the bitmap data.
The color space for the data. Pass NULL if you want to use the output color space of the context.
CIContext.hKeys in the options dictionary for a CIContext object.
extern NSString *kCIContextOutputColorSpace; extern NSString *kCIContextWorkingColorSpace; extern NSString *kCIContextUseSoftwareRenderer;
kCIContextOutputColorSpaceA key for the color space to use for images before they are rendered to the context. By default, Core Image uses the GenericRGB color space, which leaves color matching to the system. You can specify a different output color space by providing a Quartz 2D CGColorSpace object (CGColorSpaceRef). (See Quartz 2D Programming Guide for information on creating and using CGColorSpace objects.)
kCIContextWorkingColorSpaceA key for the color space to use for image operations. By default, Core Image assumes that processing nodes are 128 bits-per-pixel, linear light, premultiplied RGBA floating-point values that use the GenericRGB color space. You can specify a different working color space by providing a Quartz 2D CGColorSpace object (CGColorSpaceRef). Note that the working color space must be RGB-based. If you have YUV data as input (or other data that is not RGB-based), you can use ColorSync functions to convert to the working color space. (See Quartz 2D Programming Guide for information on creating and using CGColorSpace objects.)
kCIContextUseSoftwareRendererA key for enabling software renderer use. If the associated NSNumber object is YES, then the software renderer is required.
CIContext.hLast updated: 2007-03-16
Mac OS X Reference Library Graphics & Animation: 2D Drawing CIContext Class Reference