截取图片和缩小图片

//截取屏幕的图片
-(NSString * )ScreenShotImage:(float )insertX insertSecond:(float)insertY  insertThird:(float)width insertFour:(float)height{ 
    // 获取截取块
    UIGraphicsBeginImageContext(webView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSaveGState(context);
    // 截取图片
    UIRectClip(CGRectMake(insertX, insertY, width, height));
    [webView.layer renderInContext:context];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    CGImageRef subImageRef = CGImageCreateWithImageInRect(image.CGImage, CGRectMake(insertX,insertY, width, height));
    UIImage *subImage = [UIImage imageWithCGImage:subImageRef];
    // 5、关闭上下文
    UIGraphicsEndImageContext();
    NSData *beforeData = UIImageJPEGRepresentation(subImage, 1.0f);
    UIImage *saveImage = [UIImage imageWithData:beforeData];
    while (beforeData.length/1024 > 45) {
        beforeData = UIImageJPEGRepresentation(subImage, 0.30f);
        saveImage = [UIImage imageWithData:beforeData];
    }
    saveImage = [self compressImage:saveImage toTargetWith:width/3];
    NSData *afterData = UIImageJPEGRepresentation(saveImage, 1.0f);
//    UIImageWriteToSavedPhotosAlbum(saveImage, nil, nil, nil);//保存图片到照片库
    NSString *dataString = [NSString stringWithFormat:@"%@",[afterData base64EncodedStringWithOptions: 0]];
    return dataString;
}
// 缩小图片
- (UIImage *)compressImage:(UIImage *)sourceImage toTargetWith:(CGFloat)targetWidth{   
    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;
    CGFloat targetheight = (targetWidth / width) * height;
    UIGraphicsBeginImageContext(CGSizeMake(targetWidth, targetheight));
    [sourceImage drawInRect:CGRectMake(0, 0, targetWidth, targetheight)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndPDFContext();
    return newImage;
}