如何在一个圆圈中定位和裁剪 UIImage

Question

我有一个界面，可让您将图像定位在一个圆圈内，然后当您确定它在正确的位置时，按下裁剪按钮并裁剪图像的可见区域。

在结构上，我有一个包含滚动视图的视图，该滚动视图包含 UIImageView。 第一个视图层有一个形状层作为一个形状为圆形的蒙版。这是我的初始化代码。

- (void)viewDidLoad
{
    [super viewDidLoad];


_buttonView = [[UIView alloc]initWithFrame:CGRectMake(0, self.view.height - 136, 320, 136)];

[_buttonView setBackgroundColor:[UIColor whiteColor]];
_saveButton = [UIButton buttonWithType:UIButtonTypeCustom];
[_saveButton setTitle:@"Save image" forState:UIControlStateNormal];
[_saveButton setBackgroundImage:[[UIImage imageNamed:@"cntnt-button-defult-dark-grey.png"] resizableImageWithNormalCapInsets]  forState:UIControlStateNormal];
[_saveButton addTarget:self action:@selector(saveImageWasPressed:) forControlEvents:UIControlEventTouchUpInside];
[_saveButton setBackgroundImage:[[UIImage imageNamed:@"cntnt-button-pressed-dark-grey.png"] resizableImageWithNormalCapInsets]  forState:UIControlStateHighlighted];
[_saveButton setFrame:CGRectMake(10, 11, 300, 50)];
[_buttonView addSubview:_saveButton];


_cancelButton = [UIButton buttonWithType:UIButtonTypeCustom];
[_cancelButton setTitle:@"CANCEL" forState:UIControlStateNormal];
[_cancelButton setBackgroundImage:[[UIImage imageNamed:@"btm-button-defult-grey.png"] resizableImageWithNormalCapInsets]  forState:UIControlStateNormal];
[_cancelButton setBackgroundImage:[[UIImage imageNamed:@"btm-button-pressed-grey.png"] resizableImageWithNormalCapInsets]  forState:UIControlStateHighlighted];
[_cancelButton setFrame:CGRectMake(10, _saveButton.bottom+7, 300, 50)];
[_buttonView addSubview:_cancelButton];


[self.view addSubview:_buttonView];

_topView = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 320, _buttonView.yOrigin)];
[self.view addSubview:_topView];


_scrollView = [[UIScrollView alloc]initWithFrame:_topView.bounds];
[self.topView addSubview:_scrollView];
[_scrollView setDecelerationRate:0.0];


_imageView = [[UIImageView alloc]initWithFrame:CGRectZero];
[_scrollView addSubview:_imageView];


UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(10, (self.topView.height - 300)/2, 300, 300)];
_imageOverlay = [CAShapeLayer layer];
[_imageOverlay setPath:path.CGPath];
[_imageOverlay setFrame:CGRectMake(0, 0, 320, 320)];
[_topView.layer setMask:_imageOverlay];

[_imageView setImage:[UIImage imageNamed:@"portrait.jpg"]];
[_imageView setSize:_imageView.image.size];
[_scrollView setContentOffset:_imageView.center];
[_scrollView setContentSize:_imageView.image.size];



}

按下“_saveButton”时，我希望在 _imageOverlay 的可见部分所在的位置裁剪图像。

如果您对以上内容有任何疑问，请随时提出。 你能帮帮我吗？

Answer 1

将视图裁剪为圆形后（下面的渲染视图）：

-(UIImage *)retrieveSingletonImage:(UIView *)renderingView
{
    UIGraphicsBeginImageContextWithOptions(renderingView.bounds.size, renderingView.opaque, 0.0);

    [renderingView.layer renderInContext: UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();
    return viewImage;
}

在renderingView上使用QuartzCore层的圆角半径使其成为一个圆（直径/2 =角）

Answer 2

我在网上找到了一些可以完成这项工作的 sn-ps。 首先，我在代表我的圆形叠加层的矩形中裁剪图像

- (UIImage *)getCroppedImage
{
    float zoomScale = 1.0 / [_scrollView zoomScale];
    CGRect rect;
    rect.origin.x = [_scrollView contentOffset].x * zoomScale;
    rect.origin.y = [_scrollView contentOffset].y * zoomScale;
    rect.size.width =_imageOverlay.bounds.size.width *zoomScale;
    rect.size.height =_imageOverlay.bounds.size.height *zoomScale;

    CGImageRef cr = CGImageCreateWithImageInRect([[_imageView image] CGImage], rect);
    UIImage *cropped = [UIImage imageWithCGImage:cr];
    CGImageRelease(cr);
    return [cropped roundedCornerImage:150 borderSize:0];
}

然后在返回之前，我将图像的四角修圆并再次裁剪。

@implementation UIImage (RoundedCorner)

// Creates a copy of this image with rounded corners
// If borderSize is non-zero, a transparent border of the given size will also be added
// Original author: Björn Sållarp. Used with permission. See: http://blog.sallarp.com/iphone-uiimage-round-corners/
- (UIImage *)roundedCornerImage:(NSInteger)cornerSize borderSize:(NSInteger)borderSize {
    // If the image does not have an alpha layer, add one
    UIImage *image = [self imageWithAlpha];

    CGFloat scale = [[UIScreen mainScreen] scale];
    UIGraphicsBeginImageContextWithOptions(image.size, !image.hasAlpha, 0);

    // Build a context that's the same dimensions as the new size
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context, 0, image.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);

    // Create a clipping path with rounded corners
    CGContextBeginPath(context);
    [self addRoundedRectToPath:CGRectMake(borderSize, borderSize, image.size.width - borderSize * 2, image.size.height - borderSize * 2)
                       context:context
                     ovalWidth:cornerSize * scale
                    ovalHeight:cornerSize * scale];
    CGContextClosePath(context);
    CGContextClip(context);

    // Draw the image to the context; the clipping path will make anything outside the rounded rect transparent
    CGContextDrawImage(context, CGRectMake(0, 0, image.size.width, image.size.height), image.CGImage);

    // Create a CGImage from the context
    UIImage *roundedImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    return roundedImage;
}

@end