CGContextRef
, which is an opaque data type. After you obtain a graphics context, you can use Quartz 2D functions to draw to the context, perform operations (such as translations) on the context, and change graphics state parameters, such as line width and fill color.UIView
object and implement its drawRect:
method to perform drawing. The view’s drawRect:
method is called when the view is visible onscreen and its contents need updating. Before calling your custom drawRect:
method, the view object automatically configures its drawing environment so that your code can start drawing immediately. As part of this configuration, the UIView
object creates a graphics context (a CGContextRef
opaque type) for the current drawing environment. You obtain this graphics context in your drawRect:
method by calling the UIKit function UIGraphicsGetCurrentContext
.UIView
object modifies the CTM of the Quartz graphics context to match the UIKit conventions by translating the origin to the upper left corner of the view and inverting the y-axis by multiplying it by -1
. For more information on modified-coordinate systems and the implications in your own drawing code, see Quartz 2D Coordinate Systems.UIView
objects are described in detail in View Programming Guide for iOS.drawRect:
routine of a Cocoa application using the following line of code:currentContext
returns the NSGraphicsContext
instance of the current thread. The method graphicsPort
returns the low-level, platform-specific graphics context represented by the receiver, which is a Quartz graphics context. (Don’t get confused by the method names; they are historical.) For more information see NSGraphicsContext Class Reference.MyQuartzView
. The drawRect:
method for the view contains all the Quartz drawing code. A detailed explanation for each numbered line of code appears following the listing. drawRect:
method of the NSView
class is invoked automatically each time the view needs to be drawn. To find out more about overriding the drawRect:
method, see NSView Class Reference.0,0
) and whose width is 200
and height is 100
. For information on drawing rectangles, see Paths.0,0
) and whose width is 100
and height is 200
.CGPDFContextCreateWithURL
, which you use when you want to specify the location for the PDF output as a Core Foundation URL. Listing 2-2 shows how to use this function to create a PDF graphics context.CGPDFContextCreate
, which you use when you want the PDF output sent to a data consumer. (For more information see Data Management in Quartz 2D.) Listing 2-3 shows how to use this function to create a PDF graphics context. UIView
object, your application should modify the CTM of the PDF graphics context to modify the coordinate system. See Quartz 2D Coordinate Systems.CGPDFContextCreateWithURL
to create a PDF graphics contextMyPDFContextCreate
function. You pass NULL
as the first parameter to use the default allocator. You also need to specify a path style, which for this example is a POSIX-style pathname.CGRect
) was passed to the MyPDFContextCreate
function and is the default page media bounding box for the PDF.CGPDFContextCreate
to create a PDF graphics context MyPDFContextCreate
function. You pass NULL
as the first parameter to use the default allocator. You also need to specify a path style, which for this example is a POSIX-style pathname.CGRect
) that was passed to the MyPDFContextCreate
function. This rectangle is the default page media bounding box for the PDF.MyPDFContextCreate
routine and draw to it. A detailed explanation for each numbered line of code appears following the listing.(0,0)
and the width and height to variables supplied by the application.MyPDFContextCreate
(See Listing 2-3) to obtain a PDF graphics context, supplying a media box and a pathname. The macro CFSTR
converts a string to a CFStringRef
data type.CGLayerRef
) are optimized for offscreen drawing because, whenever possible, Quartz caches layers on the video card. UIGraphicsBeginImageContextWithOptions
instead of using the low-level Quartz functions described here. If your application creates an offscreen bitmap using Quartz, the coordinate system used by bitmap graphics context is the default Quartz coordinate system. In contrast, if your application creates an image context by calling the function UIGraphicsBeginImageContextWithOptions
, UIKit applies the same transformation to the context’s coordinate system as it does to a UIView
object’s graphics context. This allows your application to use the same drawing code for either without having to worry about different coordinate systems. Although your application can manually adjust the coordinate transformation matrix to achieve the correct results, in practice, there is no performance benefit to doing so.CGBitmapContextCreate
to create a bitmap graphics context. This function takes the following parameters:data
. Supply a pointer to the destination in memory where you want the drawing rendered. The size of this memory block should be at least (bytesPerRow
*height
) bytes.width
. Specify the width, in pixels, of the bitmap.height
. Specify the height, in pixels, of the bitmap.bitsPerComponent
. Specify the number of bits to use for each component of a pixel in memory. For example, for a 32-bit pixel format and an RGB color space, you would specify a value of 8 bits per component. See Supported Pixel Formats.bytesPerRow
. Specify the number of bytes of memory to use per row of the bitmap.bytesPerRow
are 16-byte aligned.colorspace
. The color space to use for the bitmap context. You can provide a Gray, RGB, CMYK, or NULL color space when you create a bitmap graphics context. For detailed information on color spaces and color management principles, see Color Management Overview. For information on creating and using color spaces in Quartz, see Color and Color Spaces. For information about supported color spaces, see Color Spaces and Bitmap Layout in the Bitmap Images and Image Masks chapter.bitmapInfo
. Bitmap layout information, expressed as a CGBitmapInfo
constant, that specifies whether the bitmap should contain an alpha component, the relative location of the alpha component (if there is one) in a pixel, whether the alpha component is premultiplied, and whether the color components are integer or floating-point values. For detailed information on what these constants are, when each is used, and Quartz-supported pixel formats for bitmap graphics contexts and images, see Color Spaces and Bitmap Layout in the Bitmap Images and Image Masks chapter.calloc
function to create and clear a block of memory in which to store the bitmap data. This example creates a 32-bit RGBA bitmap (that is, an array with 32 bits per pixel, each pixel containing 8 bits each of red, green, blue, and alpha information). Each pixel in the bitmap occupies 4 bytes of memory. In Mac OS X 10.6 and iOS 4, this step can be omitted—if you pass NULL
as bitmap data, Quartz automatically allocates space for the bitmap.kCGImageAlphaPremultipliedLast
indicates that the alpha component is stored in the last byte of each pixel and that the color components have already been multiplied by this alpha value. See The Alpha Value for more information on premultiplied alpha.MyCreateBitmapContext
to create a bitmap graphics context, uses the bitmap graphics context to create a CGImage
object, then draws the resulting image to a window graphics context. Figure 2-3 shows the image drawn to the window. A detailed explanation for each numbered line of code follows the listing. (0,0)
and the width and height to variables previously declared, but whose declaration are not shown in this code.MyCreateBitmapContext
(see Listing 2-5) to create a bitmap context that is 400 pixels wide and 300 pixels high. You can create a bitmap graphics context using any dimensions that are appropriate for your application.CGImageRef
) from the bitmap graphics context.cs
), and the version of Mac OS X in which the format was first available. The pixel format is specified as bits per pixel (bpp) and bits per component (bpc). The table also includes the bitmap information constant associated with that pixel format. See CGImage Reference for details on what each of the bitmap information format constants represent.CS | Pixel format and bitmap information constant | Availability |
---|---|---|
Null | 8 bpp, 8 bpc, kCGImageAlphaOnly | Mac OS X, iOS |
Gray | 8 bpp, 8 bpc, kCGImageAlphaNone | Mac OS X, iOS |
Gray | 8 bpp, 8 bpc, kCGImageAlphaOnly | Mac OS X, iOS |
Gray | 16 bpp, 16 bpc, kCGImageAlphaNone | Mac OS X |
Gray | 32 bpp, 32 bpc, kCGImageAlphaNone |kCGBitmapFloatComponents | Mac OS X |
RGB | 16 bpp, 5 bpc, kCGImageAlphaNoneSkipFirst | Robot dj arena mac os. Mac OS X, iOS |
RGB | 32 bpp, 8 bpc, kCGImageAlphaNoneSkipFirst | Mac OS X, iOS |
RGB | 32 bpp, 8 bpc, kCGImageAlphaNoneSkipLast | Mac OS X, iOS |
RGB | 32 bpp, 8 bpc, kCGImageAlphaPremultipliedFirst | Mac OS X, iOS |
RGB | 32 bpp, 8 bpc, kCGImageAlphaPremultipliedLast | Mac OS X, iOS |
RGB | 64 bpp, 16 bpc, kCGImageAlphaPremultipliedLast | Mac OS X |
RGB | 64 bpp, 16 bpc, kCGImageAlphaNoneSkipLast | Mac OS X |
RGB | 128 bpp, 32 bpc, kCGImageAlphaNoneSkipLast |kCGBitmapFloatComponents | Mac OS X |
RGB | 128 bpp, 32 bpc, kCGImageAlphaPremultipliedLast |kCGBitmapFloatComponents | Mac OS X |
CMYK | 32 bpp, 8 bpc, kCGImageAlphaNone | Mac OS X |
CMYK | 64 bpp, 16 bpc, kCGImageAlphaNone | Mac OS X |
Puppy pilots mac os. CMYK | 128 bpp, 32 bpc, kCGImageAlphaNone |kCGBitmapFloatComponents | Mac OS X |
CGContextSetShouldAntialias
. The anti-aliasing setting is part of the graphics state.CGContextSetAllowsAntialiasing
. Pass true
to this function to allow anti-aliasing; false
not to allow it. This setting is not part of the graphics state. Quartz performs anti-aliasing when the context and the graphic state settings are set to true
.NSView
subclasses. A view is told to print by invoking its print:
method. The view then creates a graphics context that targets a printer and calls its drawRect:
method. Your application uses the same drawing code to draw to the printer that it uses to draw to the screen. It can also customize the drawRect:
call to an image to the printer that is different from the one sent to the screen.# Must exist been as trickle Outsider particularize court filiation $namespaceName = “rootcimv2mdmdmmap” $className = “MDM_Policy_Config01_Connectivity02”
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