iphone - 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 UIImageView 的 ScrollView 的 View 。
第一个 View 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];



}

当按下“_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。
你能帮我么？

Answer 1

将 View 裁剪为圆形后(下面的 renderingView):

-(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 层圆角半径使其成为圆形(直径/2 = 角)