iphone - 当我绘图时，如何摆脱行之间的 "points"？

Question

有没有一种简单的方法可以不在我的线条中绘制这些点？
我不知道为什么会有这些点，因为在绘制线条时我从未将手指从屏幕上松开。

我从绘图示例中获取了代码。

// draw a line
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {

mouseSwiped = YES;
UITouch *touch = [touches anyObject];   
CGPoint currentPoint = [touch locationInView:self.view];
currentPoint.y -= 0; // 20 only for 'kCGLineCapRound'
UIGraphicsBeginImageContext(self.view.frame.size);
//Albert Renshaw - Apps4Life
[drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brushSize); // for size
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), r, g, b, alpha); //values for R, G, B, and Alpha
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

lastPoint = currentPoint;

mouseMoved++;

if (mouseMoved == 10) {
    mouseMoved = 0;
}

    }

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


//Draw a dot
if(!mouseSwiped) {

    UIGraphicsBeginImageContext(self.view.frame.size);
    [drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brushSize);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), r, g, b, alpha);
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    CGContextFlush(UIGraphicsGetCurrentContext());
    drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}
    }

这是最终版本，每行都有独特的 alpha、颜色、画笔大小:

- (void) updateDrawingBoard 
{
UIGraphicsBeginImageContext(self.drawImage.bounds.size);

for ( NSDictionary *dict in paths ) {

   UIBezierPath *p = (UIBezierPath*)[dict objectForKey:@"path"];
   p.lineWidth = [[dict objectForKey:@"size"]floatValue];
   [[UIColor colorWithRed:[[dict objectForKey:@"red"]floatValue] 
                     green:[[dict objectForKey:@"green"]floatValue] 
                      blue:[[dict objectForKey:@"blue"]floatValue] 
                     alpha:[[dict objectForKey:@"alpha"]floatValue]] setStroke];
  [p stroke];
}
[[UIColor colorWithRed:r green:g blue:b alpha:alpha] setStroke];
[path stroke];

self.drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}

- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint touchPoint = [[touches anyObject] locationInView:self.drawImage];

path = [[UIBezierPath bezierPath] retain];
path.lineCapStyle = kCGLineCapRound;
path.lineJoinStyle = kCGLineJoinBevel;
path.lineWidth = brushSize;
[path moveToPoint:touchPoint];

[self updateDrawingBoard];
}

- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint touchPoint = [[touches anyObject] locationInView:self.drawImage];

[path addLineToPoint:touchPoint];

NSDictionary   *dict = [NSDictionary dictionaryWithObjectsAndKeys:
                        path,@"path",
                        [NSNumber numberWithFloat:r], @"red", 
                        [NSNumber numberWithFloat:g], @"green", 
                        [NSNumber numberWithFloat:b], @"blue", 
                        [NSNumber numberWithFloat:alpha], @"alpha", 
                        [NSNumber numberWithFloat:brushSize], @"size", nil];
[paths addObject:dict];
[path release];
path = nil;

[self updateDrawingBoard];
}

- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
CGPoint touchPoint = [[touches anyObject] locationInView:self.drawImage];

[path addLineToPoint:touchPoint];

[self updateDrawingBoard];
}

Answer 1

问题是你通过绘制图像来逐渐积累线条。在旧线和新线重叠的地方，您会看到过度绘制的“点”。

解决方案是将您的点累积在一条路径中，并每次使用该路径重新绘制图像。由于您将绘制一条路径，而不是多个重叠路径，因此您不应该看到这些点。

代码概要:

• 在绘图开始前的某个时间，创建 CGMutablePathRef .
• 当您获得想要添加到线路中的新点时，请使用 CGPathAddLineToPoint .
• 当需要绘制路径时，请使用 CGContextAddPath将线条添加到上下文中，然后根据需要填充或描边。您还可以使用CGContextDrawPath .

或者，您可以使用UIBezierPath而不是CGMutablePathRef ，在这种情况下，步骤是:

• 创建 UIBezierPath .
• 使用-addLineToPoint:向路径添加行。
• 使用-stroke , -fill ，与将路径绘制到上下文中类似。

如果您不习惯直接使用 CoreGraphics，这可能会更简单。

我会删除中间图像并将此代码移动到 View 类(LineDrawView或CanvasView或其他东西)中，而不是将代码留在 View Controller 中。 View 可以直接将其自身绘制到屏幕上，而不是更新图像。该 View 将具有清除路径、撤消笔画以及创建路径图像的方法。然后 View Controller 将使用它们来清除 Canvas 、撤消线条并保存绘图。您可以稍后使用配置线条样式的功能来丰富它。