jpm*_*jpm 82 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.
有线索吗？
小智 92
正如其他人所描述的,最简单的解决方案是将UIImageView放入UIScrollView.我在Interface Builder .xib文件中这样做了.
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以返回要缩放的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
{
}
在苹果文档确实描述了如何做到这一点的一个很好的工作:
Bra*_*son 84
另一种简单的方法是将你UIImageView放在一个UIScrollView. 正如我在这里描述的那样,您需要将滚动视图的contentSize设置为与您的UIImageView's大小相同.将您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,只是以稍微轻一点的方式,因为您没有完整Web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的形式出现的.这可能导致高变焦因素的模糊.对于可以重绘的内容,您可以在此处按照我的建议在捏合手势完成后提供更清晰的显示.hniels的解决方案可用于重新缩放图像.
JRV*_*JRV 48
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,当前的图像比例被重置.)
小智 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;
}
}
Aug*_*ust 19
请记住,你永远不会放大UIImage.EVER.
相反,你放大和缩小view显示的UIImage.
在这种特殊情况下,您可以选择UIView使用自定义绘图创建自定义以显示图像,UIImageView为您显示图像,或者UIWebView需要一些额外的HTML来备份它.
在所有情况下,您都需要实现touchesBegan,touchesMoved等等来确定用户尝试做什么(缩放,平移等).
这是我之前使用的解决方案,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支持网站上找到:http: //discussions.apple.com/message.jspa？messageID = 7276709#7276709
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;
}
}
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