如何在手写时创建线条的曲线

Question

我正在创建一个应用程序，并且在一部分中，我正在尝试实现手写。我已经使用了一个imageView来写，它将被保存并以pdf形式发送到服务器。我已经实现了触摸开始，移动和结束，并且使用contextAddLineToPoint，我可以在用户写东西时创建行。然而。写作有点尖刻，我试图在用户改变写作方向时（即写信时）创建曲线。我不是很想实现手写识别，只是为了平滑画出的线条。

我创建了一个“缓冲区”，由一个数组组成，当用户移动触摸时，该数组包含两个中间点。如下：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 

UITouch *touch = [touches anyObject]; 

lastPoint = [touch locationInView:drawImage]; 
NSLog(@"first touch:%@",[NSValue valueWithCGPoint:lastPoint]); 

} 

drawImage是我用来在btw上写的imageView。然后去触摸感动：

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { 
UITouch *touch = [touches anyObject]; 
currentPoint = [touch locationInView:drawImage]; 

if (movementCount<2) { 
    [pointHolderArray addObject:[NSValue valueWithCGPoint:currentPoint]]; 
    movementCount ++; 
    NSLog(@"pointHolderArray: %@",pointHolderArray); 
}else 
{  
    NSLog(@"buffer full"); 
    UIGraphicsBeginImageContext(drawImage.frame.size); 
    [drawImage.image drawInRect:drawImage.frame]; 
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); 
    CGContextSetAllowsAntialiasing(UIGraphicsGetCurrentContext(), YES); 
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 3.0); 
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.3, 0.5, 0.2, 1.0); 
    CGContextBeginPath(UIGraphicsGetCurrentContext()); 
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); 
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(),[[pointHolderArray objectAtIndex:0]CGPointValue].x,[[pointHolderArray objectAtIndex:0]CGPointValue].y); 
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), [[pointHolderArray objectAtIndex:0]CGPointValue].x,[[pointHolderArray objectAtIndex:0]CGPointValue].y); 
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), [[pointHolderArray objectAtIndex:1]CGPointValue].x,[[pointHolderArray objectAtIndex:1]CGPointValue].y); 
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), [[pointHolderArray objectAtIndex:1]CGPointValue].x,[[pointHolderArray objectAtIndex:1]CGPointValue].y); 
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y); 
    CGContextStrokePath(UIGraphicsGetCurrentContext()); 
    drawImage.image = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

    lastPoint = [touch previousLocationInView:drawImage]; 
    [pointHolderArray removeAllObjects]; 
    movementCount=0; 
} 

}

正如你可以看到，每两个点已存储的时间，我再画它们之间的界线。这使得绘图稍微困难，线条更加粗糙。

任何人都可以帮助解决这个问题，我对iOS中的图形很陌生，不确定我是否使用了正确的API，甚至是否应该使用imageView。

非常感谢

Answer 1

如何使用Pan手势识别器和GLPaint。您可以设置在viewDidLoad中是这样的：

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    UIPanGestureRecognizer *g = [[UIPanGestureRecognizer alloc]initWithTarget:self action:@selector(viewPanned:)]; 

.. 

然后，捕捉泛运动：

-(void) viewPanned:(UIPanGestureRecognizer *)g 
{ 

    CGPoint point = [g locationInView:paintView]; 
    // invert y for OpenGL 
    point.y = paintView.bounds.size.height - point.y ; 

    switch (g.state) { 
     case UIGestureRecognizerStateBegan: 
      prevPoint = point ; 
      break ; 
     case UIGestureRecognizerStateChanged: 
      [paintView renderLineFromPoint:prevPoint toPoint:point] ; 
      prevPoint = point ; 
      break ; 
     case UIGestureRecognizerStateEnded: 
      prevPoint = point ; 
      break ; 
    } 
} 

这里显示的“paintView”是你可以在苹果的样本中GLPaint例如找到PaintView实例码。该示例没有显示如何更改笔大小，但可以通过设置各种glPointSize来实现。

- (void)setBrushSize:(CGFloat)size 
{ 
    if(size <= 1.0) { 
     glPointSize(10); 
    } 
    else if (size <= 2.0) { 
     glPointSize(20); 
    } 
    else if (size <= 3.0) { 
     glPointSize(30); 
    }  
    else if (size <= 4.0) { 
     glPointSize(40); 
    }  
    .. 

希望这有助于..