Ios 如何准确地放大夹点手势上的特定点（使用多个夹点）？

我正在尝试缩放iOS应用程序中的四边形。它不需要基于四边形的中心进行缩放，而是基于收缩的质心进行缩放

我能够正确地执行此操作-但仅限于第一个捏手势。在随后的挤压动作中，它是有效的，但它有一点漂移，看起来不太准确。我不知道该怎么办。

关于这一点，有几个问题，我已经讨论了大部分，如果不是全部的话。没有一个能准确地解决我的问题

还请注意，我正在缩放和转换四边形（渲染为GLKView），而不是视图本身。我见过的大多数解决方案都是直接转换视图的

以下是挤压手势和操作的代码： viewDidLoad中的第一个：

UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc]
                                             initWithTarget:self action:@selector(respondToPinchGesture:)];
pinchRecognizer.cancelsTouchesInView = YES;
pinchRecognizer.delaysTouchesEnded = NO;
[glView addGestureRecognizer:pinchRecognizer];

其中glView是GLKView对象。 和处理程序：

- (IBAction)respondToPinchGesture:(UIPinchGestureRecognizer *)recognizer{

    if (recognizer.state == UIGestureRecognizerStateEnded || [recognizer numberOfTouches] < 2) return;

    if (recognizer.state == UIGestureRecognizerStateBegan) {
        point = [recognizer locationInView:glView];
        point.x *= glView.contentScaleFactor;
        point.y *= glView.contentScaleFactor;
        point.y = height - point.y;

        anchor = GLKVector3Make(point.x, point.y, 0);
        lastScale = 1.0;
    }

    if (fabs(recognizer.scale - lastScale) > 0.01){

        GLfloat scale = 1.0 - (lastScale - recognizer.scale);
        lastScale = recognizer.scale;

        new_anchor_point = anchor;
        new_anchor_point = GLKVector3MultiplyScalar(new_anchor_point, scale);
        GLKVector3 translate = GLKVector3Subtract(anchor, new_anchor_point);

        path.transform = GLKMatrix4TranslateWithVector3(path.transform, translate);
        path.transform = GLKMatrix4Scale(path.transform, scale, scale, 0);

        cumulative_translate = GLKVector3Add(cumulative_translate, translate);
    }

}

-（iAction）响应topinch手势：（UIPinchGestureRecognizer*）识别器{
if（recognizer.state==UIgestureRecognitizerStateEnded | |[recognizer numberoftoffices]<2）返回；
if（recognizer.state==UIgestureRecognitizerStateStart）{
点=[识别器位置视图：glView]；
point.x*=glView.contentScaleFactor；
point.y*=glView.contentScaleFactor；
点y=高度-点y；
锚定=GLKVector3Make（点x，点y，0）；
lastScale=1.0；
}
if（fabs（识别器刻度-最后刻度）>0.01）{
GLfloat scale=1.0-（lastScale-recognizer.scale）；
lastScale=recognizer.scale；
新锚定点=锚定点；
新锚定点=GLKVector3多重刻度（新锚定点，刻度）；
GLKVector3 translate=GLKVector3子域（锚定、新锚定点）；
path.transform=GLKMatrix4TranslateWithVector3（path.transform，translate）；
path.transform=glkmarix4scale（path.transform，scale，scale，0）；
累计翻译=GLKVector3Add（累计翻译，翻译）；
}
}

欢迎指点。我已经做了两天了，即使是一个模糊的建议也可能会有帮助。

你必须这样做

• 记住识别器开始时的上一个变换矩阵
• 假设视图或对象之前未进行变换，则为收缩缩放构造新的变换矩阵
• 然后，将两个矩阵连接在一起。这将是变换对象或视图的最终矩阵
你必须
• 记住识别器开始时的上一个变换矩阵
• 假设视图或对象之前未进行变换，则为收缩缩放构造新的变换矩阵
• 然后，将两个矩阵连接在一起。这将是变换对象或视图的最终矩阵

---

我通过以下方法解决了这个问题：

-(GLKVector3)get_touch_point_on_view:(UIGestureRecognizer *)recognizer{
    CGRect bounds = [glView bounds];
    CGPoint point = [recognizer locationInView:glView];
    point.y = bounds.size.height - point.y;
    return GLKVector3Make((point.x * glView.contentScaleFactor - total_translation.x)/total_scale,
                                   (point.y * glView.contentScaleFactor - total_translation.y)/total_scale, 0);
}
- (void)respondToPinchGesture:(UIPinchGestureRecognizer *)recognizer{
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        lastScale = 1.0;
    }

    [self get_touch_point_on_view:recognizer];

    if (fabs(recognizer.scale - lastScale) > 0.01){

        GLfloat scale = 1.0 - (lastScale - recognizer.scale);
        lastScale = recognizer.scale;
        total_scale *= scale;

        path.transform = GLKMatrix4TranslateWithVector3(path.transform, centroid);
        path.transform = GLKMatrix4Scale(path.transform, scale, scale, 0);
        path.transform = GLKMatrix4TranslateWithVector3(path.transform, GLKVector3Negate(centroid));
        total_translation = [self get_total_translation];

    }
}

---

我通过以下方法解决了这个问题：

-(GLKVector3)get_touch_point_on_view:(UIGestureRecognizer *)recognizer{
    CGRect bounds = [glView bounds];
    CGPoint point = [recognizer locationInView:glView];
    point.y = bounds.size.height - point.y;
    return GLKVector3Make((point.x * glView.contentScaleFactor - total_translation.x)/total_scale,
                                   (point.y * glView.contentScaleFactor - total_translation.y)/total_scale, 0);
}
- (void)respondToPinchGesture:(UIPinchGestureRecognizer *)recognizer{
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        lastScale = 1.0;
    }

    [self get_touch_point_on_view:recognizer];

    if (fabs(recognizer.scale - lastScale) > 0.01){

        GLfloat scale = 1.0 - (lastScale - recognizer.scale);
        lastScale = recognizer.scale;
        total_scale *= scale;

        path.transform = GLKMatrix4TranslateWithVector3(path.transform, centroid);
        path.transform = GLKMatrix4Scale(path.transform, scale, scale, 0);
        path.transform = GLKMatrix4TranslateWithVector3(path.transform, GLKVector3Negate(centroid));
        total_translation = [self get_total_translation];

    }
}

---

这是显而易见的。很明显我可以做变焦。问题在于随后的夹击的漂移。你真的应该仔细阅读这个问题，这是显而易见的。很明显我可以做变焦。问题在于随后的夹击的漂移。你真的应该仔细阅读这个问题。