更新:下面展示了正确的绘制矩形方法
- (void)drawRect:(CGRect)rect {
CGContextRef context = UIGraphicsGetCurrentContext();
if(layer == nil)
{
float scale = [UIScreen mainScreen].scale;
CGRect bounds = CGRectMake(0, 0, rect.size.width *scale, rect.size.height *scale);
layer = CGLayerCreateWithContext(context, bounds.size, NULL);
layerContext = CGLayerGetContext(layer);
CGContextScaleCTM(layerContext, scale, scale);
viewRect = CGRectMake(0, 0, self.bounds.size.width, self.bounds.size.height);
}
UIBezierPath *bezierPath = path.bezierPath;
CGContextAddPath(layerContext, bezierPath.CGPath);
CGContextSetLineWidth(layerContext, path.width);
CGContextSetStrokeColorWithColor(layerContext, path.color.CGColor);
CGContextSetLineCap(layerContext, kCGLineCapRound);
CGContextStrokePath(layerContext);
CGContextDrawLayerInRect(context, viewRect, layer);
self.empty = NO;
}
更新:我已经按照建议将路径添加到数组中,并按照下面的方式绘制到CGLayer中。然而,当绘制大量路径时,性能会降低。我有做错什么吗?
- (void)pan:(UIPanGestureRecognizer *)pan
{
CGPoint velocity = [pan velocityInView:self];
previousPoint2 = previousPoint1;
previousPoint1 = currentPoint;
currentPoint = [pan locationInView:self];
float velocityMagnitude = sqrtf(velocity.x * velocity.x + velocity.y * velocity.y);
float clampedVelocityMagnitude = clamp(VELOCITY_CLAMP_MIN, VELOCITY_CLAMP_MAX, velocityMagnitude);
float normalizedVelocity = (clampedVelocityMagnitude - VELOCITY_CLAMP_MIN) / (VELOCITY_CLAMP_MAX - VELOCITY_CLAMP_MIN);
float lowPassFilterAlpha = STROKE_WIDTH_SMOOTHING;
float newThickness = (STROKE_WIDTH_MAX - STROKE_WIDTH_MIN) * normalizedVelocity + STROKE_WIDTH_MIN;
self.lineWidth = self.lineWidth * lowPassFilterAlpha + newThickness * (1 - lowPassFilterAlpha);
CGPoint mid1 = midPoint(previousPoint1, previousPoint2);
CGPoint mid2 = midPoint(currentPoint, previousPoint1);
CGMutablePathRef subpath = CGPathCreateMutable();
CGPathMoveToPoint(subpath, NULL, mid1.x, mid1.y);
CGPathAddQuadCurveToPoint(subpath, NULL, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y);
CGRect bounds = CGPathGetBoundingBox(subpath);
Path *path = [[Path alloc] init];
path.width = self.lineWidth;
path.color = [UIColor redColor];
path.bezierPath = [UIBezierPath bezierPathWithCGPath:subpath];
[pathArray addObject:path];
CGPathRelease(subpath);
CGRect drawBox = bounds;
drawBox.origin.x -= self.lineWidth * 2.0;
drawBox.origin.y -= self.lineWidth * 2.0;
drawBox.size.width += self.lineWidth * 4.0;
drawBox.size.height += self.lineWidth * 4.0;
[self setNeedsDisplayInRect:drawBox];
if (pan.state == UIGestureRecognizerStateEnded | pan.state == UIGestureRecognizerStateCancelled)
{
self.lineWidth = STROKE_WIDTH_MIN;
}
}
- (void)drawRect:(CGRect)rect {
[self.backgroundColor set];
UIRectFill(rect);
CGContextRef context = UIGraphicsGetCurrentContext();
if(layer == nil)
{
float scale = [UIScreen mainScreen].scale;
CGRect bounds = CGRectMake(0, 0, rect.size.width * scale, rect.size.height * scale);
layer = CGLayerCreateWithContext(context, bounds.size, NULL);
layerContext = CGLayerGetContext(layer);
}
for(int i = 0; i < [pathArray count]; i++)
{
Path *path = [pathArray objectAtIndex:i];
UIBezierPath *bezierPath = path.bezierPath;
CGContextAddPath(layerContext, bezierPath.CGPath);
CGContextSetLineWidth(layerContext, path.width);
CGContextSetStrokeColorWithColor(layerContext, path.color.CGColor);
CGContextSetLineCap(layerContext, kCGLineCapRound);
CGContextStrokePath(layerContext);
}
CGContextDrawLayerAtPoint(context, CGPointZero, layer);
self.empty = NO;
}
我使用以下代码绘制具有可变宽度的线条,根据用户的手势速度。 它可以正常工作,但是当我接近或超过以前绘制过的线时,其线宽会更改以匹配当前手势和线的速度。 请问如何确保绘制的线保持最初绘制时的粗细?
- (void)pan:(UIPanGestureRecognizer *)pan
{
CGPoint velocity = [pan velocityInView:self];
previousPoint2 = previousPoint1;
previousPoint1 = currentPoint;
currentPoint = [pan locationInView:self];
float velocityMagnitude = sqrtf(velocity.x * velocity.x + velocity.y * velocity.y);
float clampedVelocityMagnitude = clamp(VELOCITY_CLAMP_MIN, VELOCITY_CLAMP_MAX, velocityMagnitude);
float normalizedVelocity = (clampedVelocityMagnitude - VELOCITY_CLAMP_MIN) / (VELOCITY_CLAMP_MAX - VELOCITY_CLAMP_MIN);
float lowPassFilterAlpha = STROKE_WIDTH_SMOOTHING;
float newThickness = (STROKE_WIDTH_MAX - STROKE_WIDTH_MIN) * normalizedVelocity + STROKE_WIDTH_MIN;
self.lineWidth = self.lineWidth * lowPassFilterAlpha + newThickness * (1 - lowPassFilterAlpha);
CGPoint mid1 = midPoint(previousPoint1, previousPoint2);
CGPoint mid2 = midPoint(currentPoint, previousPoint1);
CGMutablePathRef subpath = CGPathCreateMutable();
CGPathMoveToPoint(subpath, NULL, mid1.x, mid1.y);
CGPathAddQuadCurveToPoint(subpath, NULL, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y);
CGRect bounds = CGPathGetBoundingBox(subpath);
CGPathAddPath(path, NULL, subpath);
CGPathRelease(subpath);
CGRect drawBox = bounds;
drawBox.origin.x -= self.lineWidth * 2.0;
drawBox.origin.y -= self.lineWidth * 2.0;
drawBox.size.width += self.lineWidth * 4.0;
drawBox.size.height += self.lineWidth * 4.0;
if (pan.state == UIGestureRecognizerStateEnded | pan.state == UIGestureRecognizerStateCancelled)
{
self.lineWidth = STROKE_WIDTH_MIN;
}
else
{
[self setNeedsDisplayInRect:drawBox];
}
}
- (void)drawRect:(CGRect)rect {
[self.backgroundColor set];
UIRectFill(rect);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextAddPath(context, path);
CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetLineWidth(context, self.lineWidth);
CGContextSetStrokeColorWithColor(context, self.lineColor.CGColor);
CGContextStrokePath(context);
self.empty = NO;
}