Quartz2D进阶

存取上下文

`
 CGContextRef ctx = UIGraphicsGetCurrentContext();
 CGContextSaveGState(ctx);
 CGContextMoveToPoint(ctx, 80, 100);
 CGContextAddLineToPoint(ctx, 100, 200);
 [[UIColor greenColor]set];
 CGContextSetLineWidth(ctx, 5);
 CGContextStrokePath(ctx);
 
 
CGContextRestoreGState(ctx);
CGContextMoveToPoint(ctx, 50, 80);
CGContextAddLineToPoint(ctx, 200, 300);
[[UIColor redColor]set];
CGContextSetLineWidth(ctx, 20);
CGContextStrokePath(ctx);
 
 
`

矩阵操作

`
 CGContextRef ctx = UIGraphicsGetCurrentContext();
 
 
//旋转的时候,是整个layer都旋转
CGContextRotateCTM(ctx, M_PI_4/2);
//缩放比例
CGContextScaleCTM(ctx, 0.5, 1.5);
//平移,x轴,y轴
CGContextTranslateCTM(ctx, 50, 100);

CGContextAddRect(ctx, CGRectMake(150, 100, 100, 100));

CGContextAddEllipseInRect(ctx, CGRectMake(200, 200, 50, 50));


CGContextStrokePath(ctx);
 
 
`

图片剪裁

CGContextRef ctx = UIGraphicsGetCurrentContext(); CGContextAddEllipseInRect(ctx, CGRectMake(100, 100, 60, 60)); CGContextClip(ctx); UIImage *image = [UIImage imageNamed:@"12"]; [image drawAtPoint:CGPointMake(100, 100)];