获取当前加载的网页的截图

#import <UIKit/UIKit.h>

@interface UIWebView (UIImage)

/**
 *  获取当前加载的网页的截图
 *
 *  @return
 */
- (UIImage *)imageForWebView;

@end

//  UIWebView+UIImage.m
//  HLBluetoothDemo
//
//  Created by Harvey on 16/5/13.
//  Copyright © 2016年 Halley. All rights reserved.
//

#import <QuartzCore/QuartzCore.h>

#import "UIWebView+UIImage.h"

@implementation UIWebView (UIImage)

/**
 *  获取当前加载的网页的截图
 *  获取当前WebView的size,然后一屏一屏的截图后，再拼接成一张完整的图片
 *
 *  @return
 */
- (UIImage *)imageForWebView
{
    // 1.获取WebView的宽高
    CGSize boundsSize = self.bounds.size;
    CGFloat boundsWidth = boundsSize.width;
    CGFloat boundsHeight = boundsSize.height;
    
    // 2.获取contentSize
    CGSize contentSize = self.scrollView.contentSize;
    CGFloat contentHeight = contentSize.height;
    // 3.保存原始偏移量，便于截图后复位
    CGPoint offset = self.scrollView.contentOffset;
    // 4.设置最初的偏移量为(0,0);
    [self.scrollView setContentOffset:CGPointMake(0, 0)];
    
    NSMutableArray *images = [NSMutableArray array];
    while (contentHeight > 0) {
        // 5.获取CGContext 5.获取CGContext
        UIGraphicsBeginImageContextWithOptions(boundsSize, NO, 0.0);
        CGContextRef ctx = UIGraphicsGetCurrentContext();
        // 6.渲染要截取的区域
        [self.layer renderInContext:ctx];
        UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        // 7.截取的图片保存起来
        [images addObject:image];
        
        CGFloat offsetY = self.scrollView.contentOffset.y;
        [self.scrollView setContentOffset:CGPointMake(0, offsetY + boundsHeight)];
        contentHeight -= boundsHeight;
    }
    // 8 webView 恢复到之前的显示区域
    [self.scrollView setContentOffset:offset];
    
    CGFloat scale = [UIScreen mainScreen].scale;
    
    CGSize imageSize = CGSizeMake(contentSize.width * scale,
                                  contentSize.height * scale);
    // 9.根据设备的分辨率重新绘制、拼接成完整清晰图片
    UIGraphicsBeginImageContext(imageSize);
    [images enumerateObjectsUsingBlock:^(UIImage *image, NSUInteger idx, BOOL *stop) {
        [image drawInRect:CGRectMake(0,
                                     scale * boundsHeight * idx,
                                     scale * boundsWidth,
                                     scale * boundsHeight)];
    }];
    
    UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return fullImage;
}

@end