小编ben*_*ore的帖子

我想用画笔绘制透明区域,但我的代码工作得不是很好.我想有人可以帮助我.我的代码:

// Handles the start of a touch

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGRect bounds = [self bounds];
    UITouch *touch = [[event touchesForView:self] anyObject];

    if (![image isPointTransparent:[touch locationInView:self]]
       || ![image isPointTransparent:[touch previousLocationInView:self]]) 
    {
        return;
    }

firstTouch = YES;

    // Convert touch point from UIView referential to OpenGL one (upside-down flip)

location = [touch locationInView:self];
location.y = bounds.size.height - location.y;
}

// Handles the continuation of a touch.

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{  
    CGRect bounds = [self bounds];
    UITouch …