捕捉UIScrollView的可见部分后图像的透明部分

Question

我的UIScrollView上有UIImageView。您可以缩放它并裁剪可见部分。

这里是我的卡代码：

UIImage *visibleScrollImage = nil; 

    UIGraphicsBeginImageContextWithOptions(self.scrollView.bounds.size, YES, [UIScreen mainScreen].scale); 
    { 
     CGPoint offset = self.scrollView.contentOffset; 
     CGContextTranslateCTM(UIGraphicsGetCurrentContext(), -offset.x, -offset.y); 
     [self.scrollView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
     visibleScrollImage = UIGraphicsGetImageFromCurrentImageContext(); 
    } 
    UIGraphicsEndImageContext(); 

    eivc.editImage = visibleScrollImage; 

当图像不走的UIScrollView的所有可见的部分，我不知道如何捕捉图像，而UIImageView的透明部分。我试图用上下文和偏移坐标的不同尺寸来猜测，但它没有奏效，因为我显然不理解有关图像，scrollview或/和CGContext的内容。

这里有一些例子，我设置backgroundColor红色的可见性。

编辑：

现在我做了一半的解决方案 我设置imageView.frame这样

self.imageView.contentMode = UIViewContentModeScaleAspectFill; 
     CGFloat initialImageHeight = result.size.height; 
     CGFloat initialImageWidth = result.size.width; 
     CGFloat height = self.scrollView.bounds.size.height; 
     CGFloat width = self.scrollView.bounds.size.width; 
     CGFloat frameHeight = height; 
     CGFloat frameWidth = width; 

     if ((initialImageHeight/initialImageWidth) > (height/width)) { 
      frameHeight = width * initialImageHeight/initialImageWidth; 
     } else if ((initialImageHeight/initialImageWidth) < (height/width)) { 
      frameWidth = height * initialImageWidth/initialImageHeight; 
     } 

     self.imageView.frame = CGRectMake(0, 0, frameWidth, frameHeight); 
     self.imageView.image = result; 

和我做了minimumZoomScale = 1.0

它阻止图像采取不完整的滚动视图可见部分。

Answer 1

由于你的描述，我想你的需求，如enter image description here

enter image description here

第一图像是正常的，第二图像缩放图像。让你感到困惑的是，在没有imageView透明部分的情况下捕捉图像，所以当你放大imageView时，imageView的原点和边界会随之变化。你可以获取屏幕图像，然后基于imageView的坐标，计算出一个矩形，这是一个imageView，一个简短的图像，这个图像是你的imageView的图像，代码如下。

- (UIImage*)cropImage{ 
    UIImage *screenImage = [UIImage imageFromView:self]; 
    CGFloat imageViewWidth = self.imageView.frame.size.width; 
    CGFloat imageViewHeight = self.imageView.frame.size.height; 

    CGRect rect; 
    UIImage *clipImage; 

    if (type == 1) { 
     if (imageViewHeight < SCREENWIDTH) { 

      rect = CGRectMake(0, SCREENHEIGHT/2-imageViewHeight/2, SCREENWIDTH, imageViewHeight); 
     }else{ 

      rect = CGRectMake(0, SCREENHEIGHT/2-SCREENWIDTH/2, SCREENWIDTH, SCREENWIDTH); 
     } 
    }else if (type == 2){ 
     if (imageViewWidth < SCREENWIDTH) { 
      rect = CGRectMake(SCREENWIDTH/2-imageViewWidth/2, SCREENHEIGHT/2-SCREENWIDTH/2, imageViewWidth, SCREENWIDTH); 
     }else{ 

      rect = CGRectMake(0, SCREENHEIGHT/2-SCREENWIDTH/2, SCREENWIDTH, SCREENWIDTH); 
     } 
    }else{ 
      rect = CGRectMake(0, SCREENHEIGHT/2-SCREENWIDTH/2, SCREENWIDTH, SCREENWIDTH); 
    } 
    clipImage = [screenImage cropImage:screenImage inRect:rect]; 
    return clipImage; 
} 


+ (UIImage *) imageFromView:(UIView *)imageView { 
    CGFloat scale = 1; 
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)] == YES)  { 
    scale = [[UIScreen mainScreen] scale]; 
    } 
    if (scale > 1) { 
     UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, scale); 
    } else { 
     UIGraphicsBeginImageContextWithOptions(imageView.bounds.size, NO, 2); 
    } 

    CGContextRef context = UIGraphicsGetCurrentContext(); 
    [imageView.layer renderInContext: context]; 
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

    return viewImage; 
} 


- (UIImage *)cropImage:(UIImage*)image inRect:(CGRect)rect 
{ 
    double (^rad)(double) = ^(double deg) { 
     return deg/180.0 * M_PI; 
    }; 

CGAffineTransform rectTransform; 
switch (image.imageOrientation) { 
    case UIImageOrientationLeft: 
     rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(90)), 0, -image.size.height); 
     break; 
    case UIImageOrientationRight: 
     rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-90)), -image.size.width, 0); 
     break; 
    case UIImageOrientationDown: 
     rectTransform = CGAffineTransformTranslate(CGAffineTransformMakeRotation(rad(-180)), -image.size.width, -image.size.height); 
     break; 
    default: 
     rectTransform = CGAffineTransformIdentity; 
}; 
rectTransform = CGAffineTransformScale(rectTransform, image.scale, image.scale); 

CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], CGRectApplyAffineTransform(rect, rectTransform)); 
UIImage *result = [UIImage imageWithCGImage:imageRef scale:image.scale orientation:image.imageOrientation]; 
CGImageRelease(imageRef); 

return result; 

}