捕捉 UIScrollView 的可见部分后裁剪图像的透明部分

Question

我有 UIScrollView 和 UIImageView 。您可以缩放它并裁剪可见部分。

这是我的 snap 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;

当图像没有占据 UIScrollView 的所有可见部分时，我不明白如何在没有 UIImageView 透明部分的情况下拍摄图像。我试图猜测上下文和偏移坐标的不同大小，但没有成功，因为我显然不了解图像、滚动视图或/和 CGContext。

以下是一些示例，我将 backgroundColor 设置为红色以显示可见性。

编辑：

现在我做了一半的解决方案 我像这样设置 imageView.frame

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;

我设置了 minimumZoomScale = 1.0

它可以防止图像占据不完整的滚动视图可见部分。

Answer 1

正如你的描述，我猜你的需求是enter image description here

enter image description here

第一个图像是正常的，第二个图像是缩放图像。让您感到困惑的是，在没有 imageView 透明部分的情况下拍摄图像，因此当您缩放 imageView 时，imageView 的原点和边界会随之变化。你可以截屏，然后根据imageView的坐标，计算一个rect就是imageView，拍一张短图，这张图就是你的imageView的图片，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;

}