获取CGContextRef的几种方法

1.继承UIView，重写drawRect方法

CGContextRef ctx = UIGraphicsGetCurrentContext();

2.根据创建好的CALayer获取当前Layer的Context

- (CGContextRef) MyCreateBitmapContext:(CALayer*)layer
{
int pixelsWide = layer.bounds.size.width;
int pixelsHigh = layer.bounds.size.height;
CGContextRef
context = NULL;
int
bitmapByteCount;
int
bitmapBytesPerRow;
bitmapBytesPerRow
= (pixelsWide * 4);// 1
bitmapByteCount
= (bitmapBytesPerRow * pixelsHigh);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
context = CGBitmapContextCreate (NULL,// 4
pixelsWide,
pixelsHigh,
8,
// bits per component
bitmapBytesPerRow,
colorSpace,
kCGImageAlphaPremultipliedLast);
if (context== NULL)
{
return NULL;
}
CGColorSpaceRelease( colorSpace );// 6
return context;// 7
}

http://www.cocoabuilder.com/archive/cocoa/218456-drawing-an-nsimage-in-calayer.html

http://www.cocoachina.com/bbs/read.php?tid-43635.html

http://www.freeboxgame.com/freebox/technologyCampQuestion.aspx?questionid=56

http://www.cocoachina.com/bbs/m/read.php?tid=51704#read

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