当用户捏住屏幕时如何放大/缩小UIImage对象？

时间：2009-02-01 02:10:07

标签： cocoa-touch uiimage uiimagejpegrepresentation

当用户在我的应用程序上执行标准捏合操作时，我想放大/缩小UIImage对象。我目前正在使用UIImageView显示我的图像，如果该细节有任何帮助。

我正在试图弄清楚如何做到这一点，但到目前为止还没有这样的运气。

任何线索？

9 个答案:

答案 0 :(得分：91)

正如其他人所描述的，最简单的解决方案是将UIImageView放入UIScrollView。我是在Interface Builder .xib文件中完成的。

在viewDidLoad中，设置以下变量。将您的控制器设置为UIScrollViewDelegate。

- (void)viewDidLoad {
    [super viewDidLoad];
    self.scrollView.minimumZoomScale = 0.5;
    self.scrollView.maximumZoomScale = 6.0;
    self.scrollView.contentSize = self.imageView.frame.size;
    self.scrollView.delegate = self;
}

您需要实现以下方法才能返回要缩放的imageView。

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return self.imageView;
}

在iOS9之前的版本中，您可能还需要添加此空委托方法：

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
}

Apple Documentation很好地描述了如何执行此操作：

答案 1 :(得分：84)

另一种简单的方法是将UIImageView放在UIScrollView内。 As I describe here，您需要将滚动视图的contentSize设置为与UIImageView's大小相同。将控制器实例设置为滚动视图的委托，并实现viewForZoomingInScrollView:和scrollViewDidEndZooming:withView:atScale:方法以允许缩放缩放和图像平移。这实际上是Ben的解决方案所做的，只是稍微轻一点，因为你没有完整网页视图的开销。

您可能遇到的一个问题是滚动视图中的缩放是以应用于图像的变换形式出现的。这可能导致高变焦因素的模糊。对于可以重绘的内容，您可以按照我的建议here在捏合手势完成后提供更清晰的显示。此时可以使用hniels的解决方案来重新缩放图像。

答案 2 :(得分：47)

Shefali的UIImageView解决方案效果很好，但需要稍加修改：

- (void)pinch:(UIPinchGestureRecognizer *)gesture {
    if (gesture.state == UIGestureRecognizerStateEnded
        || gesture.state == UIGestureRecognizerStateChanged) {
        NSLog(@"gesture.scale = %f", gesture.scale);

        CGFloat currentScale = self.frame.size.width / self.bounds.size.width;
        CGFloat newScale = currentScale * gesture.scale;

        if (newScale < MINIMUM_SCALE) {
            newScale = MINIMUM_SCALE;
        }
        if (newScale > MAXIMUM_SCALE) {
            newScale = MAXIMUM_SCALE;
        }

        CGAffineTransform transform = CGAffineTransformMakeScale(newScale, newScale);
        self.transform = transform;
        gesture.scale = 1;
    }
}

（Shefali的解决方案有一个缺点，即它在捏合时不会连续缩放。此外，当开始新的捏合时，当前图像比例被重置。）

答案 3 :(得分：23)

下面的代码有助于在不使用UIScrollView的情况下缩放UIImageView：

-(void)HandlePinch:(UIPinchGestureRecognizer*)recognizer{
    if ([recognizer state] == UIGestureRecognizerStateEnded) {
        NSLog(@"======== Scale Applied ===========");
        if ([recognizer scale]<1.0f) {
            [recognizer setScale:1.0f];
        }
        CGAffineTransform transform = CGAffineTransformMakeScale([recognizer scale],  [recognizer scale]);
        imgView.transform = transform;
    }
}

答案 4 :(得分：19)

请记住，您永远不会放大UIImage。 EVER。

相反，您正在放大显示view的{​​{1}}。

在这种特殊情况下，您可以选择使用自定义绘图创建自定义UIImage以显示图像，UIView显示图像，或UIImageView将显示图像需要一些额外的HTML来支持它。

在所有情况下，您都需要实施UIWebView，touchesBegan等来确定用户尝试做什么（缩放，平移等）。

答案 5 :(得分：8)

这是我之前使用的解决方案，它不需要您使用UIWebView。 

- (UIImage *)scaleAndRotateImage(UIImage *)image
{
    int kMaxResolution = 320; // Or whatever

    CGImageRef imgRef = image.CGImage;

    CGFloat width = CGImageGetWidth(imgRef);
    CGFloat height = CGImageGetHeight(imgRef);


    CGAffineTransform transform = CGAffineTransformIdentity;
    CGRect bounds = CGRectMake(0, 0, width, height);
    if (width > kMaxResolution || height > kMaxResolution) {
        CGFloat ratio = width/height;
        if (ratio > 1) {
            bounds.size.width = kMaxResolution;
            bounds.size.height = bounds.size.width / ratio;
        }
        else {
            bounds.size.height = kMaxResolution;
            bounds.size.width = bounds.size.height * ratio;
        }
    }

    CGFloat scaleRatio = bounds.size.width / width;
    CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
    CGFloat boundHeight;
    UIImageOrientation orient = image.imageOrientation;
    switch(orient) {

        case UIImageOrientationUp: //EXIF = 1
            transform = CGAffineTransformIdentity;
            break;

        case UIImageOrientationUpMirrored: //EXIF = 2
            transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            break;

        case UIImageOrientationDown: //EXIF = 3
            transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;

        case UIImageOrientationDownMirrored: //EXIF = 4
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
            transform = CGAffineTransformScale(transform, 1.0, -1.0);
            break;

        case UIImageOrientationLeftMirrored: //EXIF = 5
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
            transform = CGAffineTransformScale(transform, -1.0, 1.0);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationLeft: //EXIF = 6
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
            transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
            break;

        case UIImageOrientationRightMirrored: //EXIF = 7
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeScale(-1.0, 1.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        case UIImageOrientationRight: //EXIF = 8
            boundHeight = bounds.size.height;
            bounds.size.height = bounds.size.width;
            bounds.size.width = boundHeight;
            transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
            transform = CGAffineTransformRotate(transform, M_PI / 2.0);
            break;

        default:
            [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

    }

    UIGraphicsBeginImageContext(bounds.size);

    CGContextRef context = UIGraphicsGetCurrentContext();

    if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
        CGContextScaleCTM(context, -scaleRatio, scaleRatio);
        CGContextTranslateCTM(context, -height, 0);
    }
    else {
        CGContextScaleCTM(context, scaleRatio, -scaleRatio);
        CGContextTranslateCTM(context, 0, -height);
    }

    CGContextConcatCTM(context, transform);

    CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
    UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return imageCopy;
}

该文章可在Apple Support上找到： http://discussions.apple.com/message.jspa?messageID=7276709#7276709

答案 6 :(得分：5)

Shafali和JRV的答案扩展到包括平移和捏缩放：

#define MINIMUM_SCALE 0.5
#define MAXIMUM_SCALE 6.0
@property CGPoint translation;


- (void)pan:(UIPanGestureRecognizer *)gesture {
    static CGPoint currentTranslation;
    static CGFloat currentScale = 0;
    if (gesture.state == UIGestureRecognizerStateBegan) {
        currentTranslation = _translation;
        currentScale = self.view.frame.size.width / self.view.bounds.size.width;
    }
    if (gesture.state == UIGestureRecognizerStateEnded || gesture.state == UIGestureRecognizerStateChanged) {

        CGPoint translation = [gesture translationInView:self.view];

        _translation.x = translation.x + currentTranslation.x;
        _translation.y = translation.y + currentTranslation.y;
        CGAffineTransform transform1 = CGAffineTransformMakeTranslation(_translation.x , _translation.y);
        CGAffineTransform transform2 = CGAffineTransformMakeScale(currentScale, currentScale);
        CGAffineTransform transform = CGAffineTransformConcat(transform1, transform2);
        self.view.transform = transform;
    }
}


- (void)pinch:(UIPinchGestureRecognizer *)gesture {
    if (gesture.state == UIGestureRecognizerStateEnded || gesture.state == UIGestureRecognizerStateChanged) {
//        NSLog(@"gesture.scale = %f", gesture.scale);

        CGFloat currentScale = self.view.frame.size.width / self.view.bounds.size.width;
        CGFloat newScale = currentScale * gesture.scale;

        if (newScale < MINIMUM_SCALE) {
            newScale = MINIMUM_SCALE;
        }
        if (newScale > MAXIMUM_SCALE) {
            newScale = MAXIMUM_SCALE;
        }

        CGAffineTransform transform1 = CGAffineTransformMakeTranslation(_translation.x, _translation.y);
        CGAffineTransform transform2 = CGAffineTransformMakeScale(newScale, newScale);
        CGAffineTransform transform = CGAffineTransformConcat(transform1, transform2);
        self.view.transform = transform;
        gesture.scale = 1;
    }
}

答案 7 :(得分：3)

最简单的方法是，如果你想要的只是捏缩放，就是把你的图像放在UIWebView里面（写下少量的html包装代码，引用你的图像，你基本完成了） 。更复杂的方法是使用touchesBegan，touchesMoved和touchesEnded来跟踪用户的手指，并相应地调整视图的转换属性。

答案 8 :(得分：0)

请记住，您不想放大/缩小UIImage。而是尝试放大/缩小包含UIImage视图控制器的视图。

我已经解决了这个问题。看看我的代码：

@IBAction func scaleImage(sender: UIPinchGestureRecognizer) {
        self.view.transform = CGAffineTransformScale(self.view.transform, sender.scale, sender.scale)
        sender.scale = 1
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        view.backgroundColor = UIColor.blackColor()
    }

N.B。：别忘了连接PinchGestureRecognizer。

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