iOS - 如何沿路径绘制渐变
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【中文标题】iOS - 如何沿路径绘制渐变【英文标题】:iOS - How to draw gradient along a path 【发布时间】:2017-07-20 10:17:44 【问题描述】:这是我想要达到的效果:
这是我现在的效果:
基本上,我需要沿着弧线的路径绘制渐变,而不是直线地穿过弧线。我尝试了很多方法,其中一些产生了相同的结果,但其中一些产生了与预期相去甚远的结果。
这是我现在拥有的代码:
CGFloat lineSize = 12;
CGFloat radius = self.frame.size.width/2 - lineSize;
CGContextRef ctx = UIGraphicsGetCurrentContext();
//Define gradient
CGFloat colors [] =
0.9451f, 0.5804f, 0.2431f, 1.0f,
0.9922f, 0.9490f, 0.9020f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
0.8706f, 0.9020f, 0.9412f, 1.0f,
0.2941f, 0.6863f, 0.9176f, 1.0f
;
CGColorSpaceRef baseSpace = CGColorSpaceCreateDeviceRGB();
CGGradientRef gradient = CGGradientCreateWithColorComponents(baseSpace, colors, NULL, 5);
CGColorSpaceRelease(baseSpace), baseSpace = NULL;
//Define arc angle and points
CGFloat startAngle = 3.0f/4.0f * M_PI;
CGFloat endAngle = 1.0f/4.0f * M_PI;
CGFloat a = radius * cos(45);
CGFloat o = a * tan(45);
CGFloat y = CGRectGetMidY(rect) + o;
CGPoint startPoint = CGPointMake(0, y);
CGPoint endPoint = CGPointMake(self.frame.size.width, y);
CGMutablePathRef arc = CGPathCreateMutable();
CGPathAddArc(arc, NULL, CGRectGetMidX(rect), CGRectGetMidY(rect), radius,
startAngle, endAngle, NO);
CGPathRef strokedArc = CGPathCreateCopyByStrokingPath(arc, NULL, 10, kCGLineCapButt, kCGLineJoinMiter, 10);
CGContextAddPath(ctx, strokedArc);
CGContextClip(ctx);
CGContextDrawLinearGradient(ctx, gradient, startPoint, endPoint, 0);
CGGradientRelease(gradient);
我也尝试更改此代码块:
CGMutablePathRef arc = CGPathCreateMutable();
CGPathAddArc(arc, NULL, CGRectGetMidX(rect), CGRectGetMidY(rect), radius,
startAngle, endAngle, NO);
CGPathRef strokedArc = CGPathCreateCopyByStrokingPath(arc, NULL, 10, kCGLineCapButt, kCGLineJoinMiter, 10);
CGContextAddPath(ctx, strokedArc);
CGContextClip(ctx);
CGContextDrawLinearGradient(ctx, gradient, startPoint, endPoint, 0);
CGGradientRelease(gradient);
到这个块代码:
CGContextAddArc(ctx, CGRectGetMidX(rect), CGRectGetMidY(rect), radius, startAngle, endAngle, NO);
CGContextSetLineWidth(ctx, lineSize);
CGContextSetLineCap(ctx, kCGLineCapRound);
CGContextReplacePathWithStrokedPath(ctx);
CGContextClip(ctx);
CGContextDrawLinearGradient(ctx, gradient, startPoint, endPoint, 0);
CGGradientRelease(gradient), gradient = NULL;
但仍然产生与我现在的结果相似的结果。
【问题讨论】:
【参考方案1】:尝试更改渐变值。
改变
//Define gradient
CGFloat colors [] =
0.9451f, 0.5804f, 0.2431f, 1.0f,
0.9922f, 0.9490f, 0.9020f, 1.0f,
1.0f, 1.0f, 1.0f, 1.0f,
0.8706f, 0.9020f, 0.9412f, 1.0f,
0.2941f, 0.6863f, 0.9176f, 1.0f
;
对一些对称值。喜欢
CGFloat colors [] =
1.0f, 0.9176f, 0.6863f, 0.2941f,
1.0f, 0.9412f, 0.9020f, 0.8706f,
0.7432f, 1.0f, 1.0f, 0.7432f,
0.8706f, 0.9020f, 0.9412f, 1.0f,
0.2941f, 0.6863f, 0.9176f, 1.0f
;
【讨论】:
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