当用户在我的应用程序上执行标准的捏合操作时,我希望能够放大/缩小UIImage对象。目前,我正在使用UIImageView来显示我的图像,如果这个细节有所帮助的话。
我正在尝试弄清楚如何实现这一点,但迄今为止没有成功。
有什么线索吗?
当用户在我的应用程序上执行标准的捏合操作时,我希望能够放大/缩小UIImage对象。目前,我正在使用UIImageView来显示我的图像,如果这个细节有所帮助的话。
我正在尝试弄清楚如何实现这一点,但迄今为止没有成功。
有什么线索吗?
如其他人所描述的那样,最简单的解决方案是将你的UIImageView放入一个UIScrollView中。我在Interface Builder的.xib文件中完成了这个操作。
在viewDidLoad中,设置下列变量。将你的控制器设为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;
}
你需要实现以下方法来返回你想要缩放的imageView。- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
return self.imageView;
}
在iOS9之前的版本中,您可能还需要添加这个空的代理方法:- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
}
苹果文档描述得非常好,可以帮助您完成此操作:
UIImageView
放置在一个 UIScrollView
中。如我在这里所述,需要将滚动视图的 contentSize 设置为与你的 UIImageView
的大小相同。将你的控制器实例设置为滚动视图的委托,并实现 viewForZoomingInScrollView:
和 scrollViewDidEndZooming:withView:atScale:
方法以允许捏合缩放和图片平移。这基本上就是 Ben 的解决方案所做的事情,只是以稍微更轻量级的方式,因为你没有完整 Web 视图的开销。Shefali提供的UIImageView解决方案非常好,但需要进行一些修改:
- (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的解决方案的缺点在于,在捏合时它不能连续缩放。此外,当开始一个新的捏合时,当前图像的比例尺被重置。
以下代码可帮助在不使用 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;
}
}
请记住,您永远不要对UIImage
进行缩放。
相反,您要对显示UIImage
的view
进行缩放。
在这种情况下,您可以选择创建一个自定义的UIView
,使用自定义绘图来显示图像,或者使用为您显示图像的UIImageView
或UIWebView
(后者需要一些额外的HTML支持)。
无论哪种情况,您都需要实现touchesBegan
,touchesMoved
等方法来确定用户想做什么(缩放,平移等)。
这里是我之前使用过的一种解决方案,不需要使用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;
}
Shafali和JRV的答案扩展包括平移和捏合缩放:
#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;
}
}
如果你只想要捏合缩放,最简单的方法是将图像放在UIWebView
中(编写少量html包装器代码,引用你的图像,基本上就完成了)。更复杂的方法是使用touchesBegan
、touchesMoved
和touchesEnded
来跟踪用户的手指,并相应地调整你的视图的变换属性。
请记住,您不想放大/缩小UIImage。相反,请尝试放大/缩小包含UIImage View Controller的视图。
我已经为这个问题提供了一个解决方案。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()
}
scrollViewDidEndZooming:
方法。 - Johnny