ios 本地图片合成,网络图片合成,视图转成图片,截屏功能实现

/**合成本地图片*/
UIImage *firstImage = self.firstImageView.image;

UIImage *secondImage = self.secondImageView.image;

 //以底部图片大小为画布创建上下文
UIGraphicsBeginImageContext(CGSizeMake(self.firstImageView.czh_width, self.firstImageView.czh_height));
//先把底部图片 画到上下文中
[firstImage drawInRect:self.firstImageView.frame];
//再把上面图片 放在上下文中
[secondImage drawInRect:self.secondImageView.frame];
//从当前上下文中获得最终图片
UIImage *resultImg = UIGraphicsGetImageFromCurrentImageContext();
//关闭上下文   
UIGraphicsEndImageContext();  

合成网络图片
NSString *firstUrl = @"http://static.yygo.tv/avatar/2/5a712bc7790f2.png";

    NSString *secondUrl = @"http://static.yygo.tv/avatar/2/5a5756e2dd94b.png";

    //
    czh_dispatch_queue_async_safe(dispatch_get_global_queue(0, 0), ^{

        //
        NSData *fistData = [NSData dataWithContentsOfURL:[NSURL URLWithString:firstUrl]];

        UIImage *firstImage = [UIImage imageWithData:fistData];


        CGFloat firstImageW = 0;
        CGFloat firstImageH = 0;
        if (firstImage.size.height > 0 && firstImage.size.width > 0) {

            if (firstImage.size.height > firstImage.size.width) {
                firstImageW = ScreenWidth;
                firstImageH = firstImageW * firstImage.size.height / firstImage.size.width;
            } else {
                firstImageH = ScreenWidth;
                firstImageW = firstImageH * firstImage.size.width / firstImage.size.height;
            }
        }


        NSData *secondData = [NSData dataWithContentsOfURL:[NSURL URLWithString:secondUrl]];

        UIImage *secondImage = [UIImage imageWithData:secondData];


        CGFloat secondImageW = 0;
        CGFloat secondImageH = 0;
        if (secondImage.size.height > 0 && secondImage.size.width > 0) {

            if (secondImage.size.height > secondImage.size.width) {
                secondImageW = ScreenWidth;
                secondImageH = secondImageW * secondImage.size.height / secondImage.size.width;
            } else {
                secondImageH = ScreenWidth;
                secondImageW = secondImageH * secondImage.size.width / secondImage.size.height;
            }
        }


        //固定的大小为画布创建上下文
        UIGraphicsBeginImageContext(CGSizeMake(ScreenWidth, ScreenWidth));

        [firstImage drawInRect:CGRectMake((ScreenWidth - firstImageW)*0.5, (ScreenWidth - firstImageH)* 0.5, firstImageW, firstImageH)];//先把网络封面图片放在下面

        [secondImage drawInRect:CGRectMake((ScreenWidth - secondImageW * 0.5)*0.5, (ScreenWidth - secondImageH * 0.5)*0.5, secondImageW * 0.5, secondImageH * 0.5)];//再把小图放在上面

        //需要合成更多，继续添加

        UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();//从当前上下文中获得最终图片
        UIGraphicsEndImageContext();//关闭上下文

        czh_dispatch_main_sync_safe(^{

            [CZHShowSyntheticImageView czh_showSyntheticImageViewWithImage:resultImage];
        });


    });

//把视图生成图片
+ (UIImage *)czh_generateImageWithView:(UIView *)view {

    CGSize size = view.bounds.size;

    // 下面方法，第一个参数表示区域大小。第二个参数表示是否是非透明的。如果需要显示半透明效果，需要传NO，否则传YES。第三个参数就是屏幕密度了，关键就是第三个参数。

    UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);

    [view.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return image;
}

截图功能，首先监听通知
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(userDidTakeScreenshot:) name:UIApplicationUserDidTakeScreenshotNotification object:nil];

然后获取当前页面生成图片
////截取当前屏幕
+ (UIImage *)czh_generateScreenShotImage {

    CGSize imageSize = CGSizeZero;
    imageSize = [UIScreen mainScreen].bounds.size;

    UIGraphicsBeginImageContextWithOptions(imageSize, NO, [UIScreen mainScreen].scale);

    CGContextRef context = UIGraphicsGetCurrentContext();

    for (UIWindow *window in [[UIApplication sharedApplication] windows]) {

        CGContextSaveGState(context);
        CGContextTranslateCTM(context, window.center.x, window.center.y);
        CGContextConcatCTM(context, window.transform);
        CGContextTranslateCTM(context, -window.bounds.size.width * window.layer.anchorPoint.x, -window.bounds.size.height * window.layer.anchorPoint.y);

        if ([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)]) {

            [window drawViewHierarchyInRect:window.bounds afterScreenUpdates:YES];

        } else {

            [window.layer renderInContext:context];

        }
        CGContextRestoreGState(context);
    }

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    NSData *imageData = UIImagePNGRepresentation(image);

    return [UIImage imageWithData:imageData];

}

简书地址
github地址

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