在iOS中的iPad上捏缩放将图像移动到最左角？

Posted 2023-02-19

【中文标题】在iOS中的iPad上捏缩放将图像移动到最左角？

【英文标题】：Pinch zoom shifting image to most left corner on iPad in iOS?

【发布时间】：2016-01-30 17:14:14

【问题描述】：

我在 ios 中有一张图片。当我捏住它移动到左上角的图像时，我在图像上添加了捏合手势。我还在图像上添加了平移手势。当图像被缩放时，我会向各个方向滚动图像，为此我已将平移手势添加到图像中。

我的代码是：

-(void)viewDidLoad

UIPinchGestureRecognizer *pinch=[[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(handlePinch:)];
            [self.zoom_image addGestureRecognizer:pinch];
            panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(moveImage:)];
            [panGesture setMinimumNumberOfTouches:1];
            [panGesture setMaximumNumberOfTouches:1];
            [self.zoom_image addGestureRecognizer:panGesture];

            img_center_x = self.zoom_image.center.x;
            img_center_y = self.zoom_image.center.y;



-(void)handlePinch:(UIPinchGestureRecognizer*)sender

    NSLog(@"latscale = %f",mLastScale);
    mCurrentScale += [sender scale] - mLastScale;
    mLastScale = [sender scale];
    NSLog(@"before ceneter x %f",img_center_x);
    NSLog(@"before ceneter x %f",img_center_y);
    CGPoint img_center = CGPointMake(img_center_x, img_center_y);
    self.zoom_image.center = img_center;
    if (sender.state == UIGestureRecognizerStateEnded)
    
      mLastScale = 1.0;
    
    if(mCurrentScale<1.0)
    
        mCurrentScale=1.0;
    
    if(mCurrentScale>3.0)
    
        mCurrentScale=3.0;
    
    CGAffineTransform currentTransform = CGAffineTransformIdentity;
    CGAffineTransform newTransform = CGAffineTransformScale(currentTransform,mCurrentScale, mCurrentScale);
    self.zoom_image.transform = newTransform;

平移手势

 UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(moveImage:)];
            [panGesture setMinimumNumberOfTouches:1];
            [panGesture setMaximumNumberOfTouches:1];
            [self.zoom_image addGestureRecognizer:panGesture];

move image:

- (void)moveImage:(UIPanGestureRecognizer *)recognizer

    CGPoint translation = [recognizer translationInView:self.zoom_image];
    CGPoint location = [recognizer locationInView:self.view];
    CGPoint initial=CGPointZero;
    NSLog(@"%f\n%f",translation.x,translation.y);
    NSLog(@"%f",self.zoom_image.frame.origin.y);
    CGPoint finalpoint = CGPointMake(self.zoom_image.center.x + translation.x, self.zoom_image.center.y+ translation.y);
    NSLog(@"%f",finalpoint.y);
    //limit the boundary
    if(recognizer.state==UIGestureRecognizerStateChanged)
    
        if ((self.zoom_image.frame.origin.x>0 && translation.x > 0) || (self.zoom_image.frame.origin.x + self.zoom_image.frame.size.width<=self.view.frame.size.width && translation.x < 0))
            finalpoint.x = self.zoom_image.center.x;

        if ((self.zoom_image.frame.origin.y>100 && translation.y > 0) || (self.zoom_image.frame.origin.y + self.zoom_image.frame.size.height<=self.view.frame.size.height && translation.y < 0))
            finalpoint.y = self.zoom_image.center.y;
        //set final position
        NSLog(@"%f",finalpoint.y);
        self.zoom_image.center = finalpoint;
        [recognizer setTranslation:initial inView:self.zoom_image];
    

【参考方案1】：

这是一个可能的解决方案。

• 我已将您的 zoom_image 重命名为 contentView，因为此类可以操作任何视图，而不仅仅是图像。

• 我已经删除了绑定测试，并将比例设为 (0.01 - 10.0)

• 最多三个手指的捏合手柄，也可用作平移。可以在不中断捏合的情况下更改触摸次数。

还有很多需要改进的地方，但主要的原则在这里:)

接口（如 minScale、maxScale、minMargin 等属性仍有待添加 - 为什么不是委托）

@interface PinchViewController : UIViewController

@property(nonatomic,strong) IBOutlet UIView* contentView;

@end

实施

@implementation PinchViewController

    CGPoint translation;
    CGFloat scale;

    CGAffineTransform scaleTransform;
    CGAffineTransform translateTransform;

    CGPoint     previousTranslation;
    CGFloat     previousScale;
    NSUInteger  previousNumTouches;


-(void)viewDidLoad

    scale = 1.0f;
    scaleTransform = CGAffineTransformIdentity;
    translateTransform = CGAffineTransformIdentity;
    previousTranslation = CGPointZero;
    previousNumTouches = 0;

    UIPinchGestureRecognizer *pinch=[[UIPinchGestureRecognizer alloc]initWithTarget:self action:@selector(handlePinch:)];
    [self.view addGestureRecognizer:pinch];

    UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
    [panGesture setMinimumNumberOfTouches:1];
    [panGesture setMaximumNumberOfTouches:1];
    [self.view addGestureRecognizer:panGesture];



-(void)handlePinch:(UIPinchGestureRecognizer*)recognizer

    // 1 - find pinch center
    CGPoint mid = [self computePinchCenter:recognizer];
    mid.x-= recognizer.view.bounds.size.width / 2.0f;
    mid.y-= recognizer.view.bounds.size.height / 2.0f;

    // 2 - compute deltas
    NSUInteger numTouches = recognizer.numberOfTouches;
    if ( (recognizer.state==UIGestureRecognizerStateBegan)  || ( previousNumTouches != numTouches ) ) 
        previousScale = recognizer.scale;
        previousTranslation = mid;
        previousNumTouches = numTouches;
    

    CGFloat deltaScale = ( recognizer.scale - previousScale ) * scale;
    previousScale = recognizer.scale;

    CGPoint deltaTranslation = CGPointMake(mid.x-previousTranslation.x, mid.y-previousTranslation.y);
    previousTranslation = mid;

    deltaTranslation.x/=scale;
    deltaTranslation.y/=scale;

    // 3 - apply
    scale+=deltaScale;

    if (scale<0.01) scale = 0.01; else if (scale>10) scale = 10;

    scaleTransform = CGAffineTransformMakeScale(scale, scale);
    [self translateBy:deltaTranslation];

    NSLog(@"Translation : %.2f,%.2f - Scale Center : %.2f,%.2f - Scale : %.2f",deltaTranslation.x,deltaTranslation.y,mid.x,mid.y,scale);


- (void)handlePan:(UIPanGestureRecognizer *)recognizer

    if (recognizer.state==UIGestureRecognizerStateBegan) previousTranslation = CGPointZero;
    CGPoint recognizerTranslation = [recognizer translationInView:self.contentView];
    CGPoint deltaTranslation = CGPointMake(recognizerTranslation.x - previousTranslation.x,recognizerTranslation.y - previousTranslation.y);
    previousTranslation = recognizerTranslation;
    [self translateBy:deltaTranslation];

    NSLog(@"Translation : %.2f,%.2f - Scale : %.2f",deltaTranslation.x,deltaTranslation.y,scale);



-(void)translateBy:(CGPoint)delta

    translation.x+=delta.x;
    translation.y+=delta.y;
    translateTransform = CGAffineTransformMakeTranslation(translation.x,translation.y);
    self.contentView.transform = CGAffineTransformConcat(translateTransform,scaleTransform);


-(CGPoint)computePinchCenter:(UIPinchGestureRecognizer*)recognizer

    // 1 - handle up to 3 touches
    NSUInteger numTouches = recognizer.numberOfTouches;
    if (numTouches>3) numTouches = 3;

    // 2 - Find fingers middle point - with (0,0) being the center of the view
    CGPoint pt1,pt2,pt3,mid;
    switch (numTouches) 
        case 3:
            pt3 = [recognizer locationOfTouch:2 inView:recognizer.view];
        case 2:
            pt2 = [recognizer locationOfTouch:1 inView:recognizer.view];
        case 1:
            pt1 = [recognizer locationOfTouch:0 inView:recognizer.view];
    
    switch (numTouches) 
        case 3:
            mid = CGPointMake( ( ( pt1.x + pt2.x ) / 2.0f + pt3.x ) / 2.0f, ( ( pt1.y + pt2.y ) / 2.0f + pt3.y ) / 2.0f );
            break;
        case 2:
            mid = CGPointMake( ( pt1.x + pt2.x ) / 2.0f, ( pt1.y + pt2.y ) / 2.0f  );
            break;
        case 1:
            mid = CGPointMake( pt1.x, pt1.y);
            break;
    
    return mid;


@end

希望它会有所帮助:) 干杯

【讨论】：

对……这是一个快速的猜测。我已经睡过了。我用一种可能的方式进行编辑和替换。

是的 - 第一个解决方案是快速猜测，但不起作用。编辑后的答案有效，并且仍然允许很多改进。

有哪些改进？

使用诸如 minScale、maxScale 之类的属性设置限制... 捏合算法已经很好地工作了，但是在缩放时手指的中心并不完全静止。它应该，但我不能花更多的时间在它上面:)

顺便说一句，我投票赞成你的问题，因为那是一个有趣的挑战；）再见！