iphone – 使用OpenGL在iPad上绘制应用程序

CGPoint drawBezier(CGPoint origin,CGPoint control,CGPoint destination,int segments)
{
 CGPoint vertices[segments/2];
 CGPoint midPoint;
 glDisable(GL_TEXTURE_2D);
 float x,y;

 float t = 0.0;
 for(int i = 0; i < (segments/2); i++)
 {
  x = pow(1 - t,2) * origin.x + 2.0 * (1 - t) * t * control.x + t * t * destination.x;
  y = pow(1 - t,2) * origin.y + 2.0 * (1 - t) * t * control.y + t * t * destination.y;
  vertices[i] = CGPointMake(x,y);
  t += 1.0 / (segments);

 }
 //windowHeight is the height of you drawing canvas.
 midPoint = CGPointMake(x,windowHeight - y);
 glVertexPointer(2,GL_FLOAT,vertices);
 glDrawArrays(GL_POINTS,segments/2);
 return midPoint;
}

这将以三点为基础.控制是中点,您需要返回.新的中点将与之前的不同.另外,如果你通过上面的代码,它只会画一半.下一个笔画将填写.这是必需的.我的代码调用这个函数(以上是在C中,这在Obj-C中)：

//Invert the Y axis to conform the iPhone top-down approach
   invertedYBegCoord = self.bounds.size.height - [[currentStroke objectAtIndex:i] CGPointValue].y;
   invertedYEndCoord = self.bounds.size.height - [[currentStroke objectAtIndex:i+1] CGPointValue].y;
   invertedYThirdCoord = self.bounds.size.height - [[currentStroke objectAtIndex:i+2] CGPointValue].y;
   //Figure our how many dots you need
   count = MAX(ceilf(sqrtf(([[currentStroke objectAtIndex:i+2] CGPointValue].x - [[currentStroke objectAtIndex:i] CGPointValue].x) 
         * ([[currentStroke objectAtIndex:i+2] CGPointValue].x - [[currentStroke objectAtIndex:i] CGPointValue].x) 
         + ((invertedYThirdCoord - invertedYBegCoord) * (invertedYThirdCoord - invertedYBegCoord))) / pointCount),1);

   newMidPoint = drawBezier(CGPointMake([[currentStroke objectAtIndex:i] CGPointValue].x,invertedYBegCoord),CGPointMake([[currentStroke objectAtIndex:i+1] CGPointValue].x,invertedYEndCoord),CGPointMake([[currentStroke objectAtIndex:i+2] CGPointValue].x,invertedYThirdCoord),count);

   int loc = [currentStroke count]-1;
   [currentStroke insertObject:[NSValue valueWithCGPoint:newMidPoint] atIndex:loc];
   [currentStroke removeObjectAtIndex:loc-1];

该代码将基于倒置的iPad点获得中点,并将“控件”设置为当前点.

这将平滑边缘.现在关于线宽,你只需要找到该图的速度.找到你的线的长度是最简单的.这很容易使用组件数学.我没有任何代码,但here是来自物理网站的组件数学的底稿.或者你可以简单地划分(上面)计数一些数字,以找出你需要多大的行(计数使用组件数学).

我将点数据存储在名为currentStroke的数组中,以防不明显.

这应该是你需要的.

编辑：

要存储点,你应该使用touchesBegin和touchesEnd：

- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event
{
    self.currentStroke = [NSMutableArray array];
    CGPoint point = [ [touches anyObject] locationInView:self];
    [currentStroke addObject:[NSValue valueWithCGPoint:point]];
    [self draw];

}

- (void) touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    CGPoint point = [ [touches anyObject] locationInView:self];
    [currentStroke addObject:[NSValue valueWithCGPoint:point]];
    [self draw];
}


- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint point = [ [touches anyObject] locationInView:self];
    [currentStroke addObject:[NSValue valueWithCGPoint:point]];
    [self draw];
}

这几乎是整个绘图应用程序.如果您使用GL_Paint,那么您已经在使用该系统构建的点精灵.