CALayer绘图

// 通过CALayer的代理方法进行绘图，可用于社交app的头像应用
//  CALayerGraphicsViewController.m
//  CALayerGraphics
//
//  Created by xiaoyao on 15/3/6.
//  Copyright (c) 2015年 lijien. All rights reserved.
//

#import "CALayerGraphicsViewController.h"

#define PHOTO_HEIGHT 150

@interface CALayerGraphicsViewController ()

@end

@implementation CALayerGraphicsViewController

- (void)viewDidLoad {
  [super viewDidLoad];
  
  [self myCalyerGraphics];
}

- (void)myCalyerGraphics {
  CALayer *layer = [[CALayer alloc] init];
  layer.bounds = CGRectMake(0, 0, PHOTO_HEIGHT, PHOTO_HEIGHT);
  layer.position = CGPointMake(160, 200);
  layer.backgroundColor = [UIColor redColor].CGColor;
  
  layer.cornerRadius = PHOTO_HEIGHT / 2;
  layer.borderColor = [UIColor whiteColor].CGColor;
  layer.borderWidth = 2;
  layer.masksToBounds = YES;
  
  layer.delegate = self;
  
  [self.view.layer addSublayer:layer];
  
  // 必须调用，否则图层上绘制的内容无法显示，并且图层的代理方法也不会调用
  [layer setNeedsDisplay];
}

#pragma mark - calayerDlelegte 
- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
  CGContextSaveGState(ctx);
  
  CGContextScaleCTM(ctx, 1, -1);
  CGContextTranslateCTM(ctx, 0, -PHOTO_HEIGHT);
  
  UIImage *image = [UIImage imageNamed:@"photo.png"];
  
  CGContextDrawImage(ctx, CGRectMake(0, 0, PHOTO_HEIGHT, PHOTO_HEIGHT), image.CGImage);
  
  CGContextRestoreGState(ctx);
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
  UITouch *touch = [touches anyObject];
  CALayer *calayer = self.view.layer.sublayers[0];
  
  CGFloat width = calayer.bounds.size.width;
  if (width == PHOTO_HEIGHT) {
    width = PHOTO_HEIGHT * 2;
  } else {
    width = PHOTO_HEIGHT;
  }
  
  calayer.bounds = CGRectMake(0, 0, width, width);
  calayer.position = [touch locationInView:self.view];
  calayer.cornerRadius = width / 2;
}
@end

原文：http://blog.csdn.net/u010606986/article/details/44100533