UIView的无损截图

说明

1. 烂大街的代码

2. 写成category后，方便直接从drawRect中获取绘制出来的图片

3. 可以直接绘制图片供按钮设置背景图片用

4. 无损截图（包括alpha通道值也被无损保存）

源码

//
//  UIView+ScreensShot.h
//  ColorfulView
//
//  Created by YouXianMing on 15/7/17.
//  Copyright (c) 2015年 YouXianMing. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface UIView (ScreensShot)

/**
 *  无损截图
 *
 *  This function may be called from any thread of your app.
 *
 *  @return 返回生成的图片
 */
- (UIImage *)screenShot;

@end

//
//  UIView+ScreensShot.m
//  ColorfulView
//
//  Created by YouXianMing on 15/7/17.
//  Copyright (c) 2015年 YouXianMing. All rights reserved.
//

#import "UIView+ScreensShot.h"
#import <objc/runtime.h>

@implementation UIView (ScreensShot)

- (UIImage *)screenShot {

    if (self && self.frame.size.height && self.frame.size.width) {

        UIGraphicsBeginImageContextWithOptions(self.frame.size, NO, 0);
        [self.layer renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();

        return image;

    } else {

        return nil;
    }

}

@end

//
//  ViewController.m
//  ColorfulView
//
//  Created by YouXianMing on 15/7/10.
//  Copyright (c) 2015年 YouXianMing. All rights reserved.
//

#import "ViewController.h"
#import "UIView+ScreensShot.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.view.backgroundColor = [UIColor blackColor];

    UIView *cyanView         = [[UIView alloc] initWithFrame:CGRectMake(30, 30, 100, 100)];
    cyanView.backgroundColor = [UIColor cyanColor];
    cyanView.alpha           = 0.5f;
    [self.view addSubview:cyanView];

    UIImageView *imageView   = [[UIImageView alloc] initWithImage:[cyanView screenShot]];
    imageView.frame          = CGRectMake(80, 80, 100, 100);
    [self.view addSubview:imageView];
}

@end