在可缩放的视图上绘图

我正在研究一个小的绘图应用程序，它具有支持放大/缩小的基本要求。 我有两个主要问题：

1. 当视图放大/变形时，绘图不会显得清晰明了。 有没有更好的方法，还是有一种方法来改善视图缩放时的绘图？

2. 在1200 x 1200磅的canvas上（在iPhone上）绘图时，绘图性能较差。 任何机会，我可以改善它的大帆布尺寸？

缩放代码：

- (void)scale:(UIPinchGestureRecognizer *)gestureRecognizer { [self adjustAnchorPointForGestureRecognizer:gestureRecognizer]; UIView *canvas = [gestureRecognizer view]; if ([gestureRecognizer state] == UIGestureRecognizerStateBegan || [gestureRecognizer state] == UIGestureRecognizerStateChanged) { // Calculate the drawing view's size CGSize drawingViewSize = ...; // Calculate the minimum allowed tranform size // Developer's Note: I actually wanted to use the size 1/4th of the view // but self.view.frame.size doesn't return the correct (actual) width and height // It returns these values inverted ie width as height, and vice verse. // The reason is that the view appears to be transformed (90 degrees). // Since there's no work-around this, so for now, I'm just using fixed values. CGSize minTranformSize = CGSizeMake(100.0f, 100.0f); if ((minTranformSize.width > drawingViewSize.width) && (minTranformSize.height > drawingViewSize.height)) { minTranformSize = drawingViewSize; } // Transform the view, provided // 1. It won't scale more than the original size of the background image // 2. It won't scale less than the minimum possible transform CGSize transformedSize = CGSizeMake(canvas.frame.size.width * [gestureRecognizer scale], canvas.frame.size.height * [gestureRecognizer scale]); if ((transformedSize.width <= drawingViewSize.width) && (transformedSize.height <= drawingViewSize.height) && (transformedSize.width >= minTranformSize.width) && (transformedSize.height >= minTranformSize.height)) { canvas.transform = CGAffineTransformScale([canvas transform], [gestureRecognizer scale], [gestureRecognizer scale]); } [gestureRecognizer setScale:1.0]; } else if ([gestureRecognizer state] == UIGestureRecognizerStateEnded) { // Recenter the container view, if required (piece is smaller than the view and it's not aligned) CGSize viewSize = self.view.bounds.size; if ((canvas.frame.size.width < viewSize.width) || (canvas.frame.size.height < viewSize.height)) { canvas.center = CGPointMake(viewSize.width/2, viewSize.height/2); } // Adjust the x/y coordinates, if required (piece is larger than the view and it's moving outwards from the view) if (((canvas.frame.origin.x > 0) || (canvas.frame.origin.y > 0)) && ((canvas.frame.size.width >= viewSize.width) && (canvas.frame.size.height >= viewSize.height))) { canvas.frame = CGRectMake(0.0, 0.0, canvas.frame.size.width, canvas.frame.size.height); } canvas.frame = CGRectIntegral(canvas.frame); } } 

绘图代码

 - (void)draw { CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSaveGState(context); if (self.fillColor) { [self.fillColor setFill]; [self.path fill]; } if ([self.strokeColor isEqual:[UIColor clearColor]]) { [self.path strokeWithBlendMode:kCGBlendModeClear alpha:1.0]; } else if (self.strokeColor) { [self.strokeColor setStroke]; [self.path stroke]; } CGContextRestoreGState(context); } 

Answer 1

这是一个相当复杂的问题，我一直在努力挣扎。

我结束了将图纸转换为vector。

1. 在一个图层中绘制所有线条，在另一个图层中绘制所有线条。
2. 使用potrace将线条图转换为Vector（ http://potrace.sourceforge.net/ ）
3. 使用SVGKit（ https://github.com/SVGKit/SVGKit ）绘制vector，并隐藏1）中绘制的图层，

它工作得相当好，速度相当快，但是这需要很多工作。 我们在我们公司有一个应用这种技术的应用程序：

https://itunes.apple.com/us/app/ideal-paint-hd-mormor/id569450492?mt=8 。

如果你唯一的问题是性能，请尝试看看CATiledLayer 。 （也用于上面提到的应用程序）。 它会大大提高性能（你可以在这里find一个很好的教程http://www.cimgf.com/2011/03/01/subduing-catiledlayer/ ）。

祝你好运！ 🙂

Answer 2

首先你是变形视图这不是更好的缩放方式。变形可能只用于增加或减小UIVew的大小对于缩放，你可以这样做。

1）使用此代码获取屏幕图片

 UIGraphicsBeginImageContext(self.drawingView.bounds.size); CGContextRef context = UIGraphicsGetCurrentContext(); //[self.view.layer renderInContext:context]; [self.layerContainerView.layer renderInContext:context]; UIImage *screenShot = UIGraphicsGetImageFromCurrentImageContext(); [scaleLabel setHidden:FALSE]; return screenShot; 

2）然后把它放在一些UIImageView上，然后在这个图像上执行Zomming

  scrollView.userInteractionEnabled=TRUE; self.scrollView.minimumZoomScale = 1.000; self.scrollView.maximumZoomScale = 30.0f; [self centerScrollViewContents]; CGFloat newZoomScale = self.scrollView.zoomScale / 1.5f; newZoomScale = MAX(newZoomScale, self.scrollView.minimumZoomScale); [self.scrollView setZoomScale:newZoomScale animated:YES]; 

3）然后再次在uiView的背景上设置缩放图像

这对我来说是完美的希望这也会对你有用