在 iOS 应用程序中绘制通过一组给定点的贝塞尔曲线的最佳方法是什么
最佳答案
例如,可以通过查看 BEMSimpleLineGraph GitHub Project 来实现更通用的方法。 (有关更多信息,请参见此处:bemsimplelinegraph)。在这里,我提取了一种通过给定点列表绘制贝塞尔曲线的方法。
头文件(BezierLine.h):
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import <CoreGraphics/CoreGraphics.h>
@interface BezierLine : NSObject
/*
Draws a bezier curved line on the given context
with points: Array of CGPoint values
*/
-(void) drawBezierCurveInContext:(CGContextRef)context withPoints:(NSArray*)points lineColor:(UIColor*)color lineWidth:(CGFloat)lineWidth;
@end
实现(BezierLine.m):
#import "BezierLine.h"
@implementation BezierLine
-(void) drawBezierCurveInContext:(CGContextRef)context withPoints:(NSArray*)points lineColor:(UIColor*)color lineWidth:(CGFloat)lineWidth {
if (points.count < 2) return;
CGPoint CP1;
CGPoint CP2;
// LINE
UIBezierPath *line = [UIBezierPath bezierPath];
CGPoint p0;
CGPoint p1;
CGPoint p2;
CGPoint p3;
CGFloat tensionBezier1 = 0.3;
CGFloat tensionBezier2 = 0.3;
CGPoint previousPoint1;
CGPoint previousPoint2;
[line moveToPoint:[[points objectAtIndex:0] CGPointValue]];
for (int i = 0; i < points.count - 1; i++) {
p1 = [[points objectAtIndex:i] CGPointValue];
p2 = [[points objectAtIndex:i + 1] CGPointValue];
const CGFloat maxTension = 1.0f / 3.0f;
tensionBezier1 = maxTension;
tensionBezier2 = maxTension;
if (i > 0) { // Exception for first line because there is no previous point
p0 = previousPoint1;
if (p2.y - p1.y == p1.y - p0.y) tensionBezier1 = 0;
} else {
tensionBezier1 = 0;
p0 = p1;
}
if (i < points.count - 2) { // Exception for last line because there is no next point
p3 = [[points objectAtIndex:i + 2] CGPointValue];
if (p3.y - p2.y == p2.y - p1.y) tensionBezier2 = 0;
} else {
p3 = p2;
tensionBezier2 = 0;
}
// The tension should never exceed 0.3
if (tensionBezier1 > maxTension) tensionBezier1 = maxTension;
if (tensionBezier2 > maxTension) tensionBezier2 = maxTension;
// First control point
CP1 = CGPointMake(p1.x + (p2.x - p1.x)/3,
p1.y - (p1.y - p2.y)/3 - (p0.y - p1.y)*tensionBezier1);
// Second control point
CP2 = CGPointMake(p1.x + 2*(p2.x - p1.x)/3,
(p1.y - 2*(p1.y - p2.y)/3) + (p2.y - p3.y)*tensionBezier2);
[line addCurveToPoint:p2 controlPoint1:CP1 controlPoint2:CP2];
previousPoint1 = p1;
previousPoint2 = p2;
}
CGContextSetAllowsAntialiasing(context, YES);
CGContextSetStrokeColorWithColor(context, color.CGColor);
CGContextSetLineWidth(context, lineWidth);
CGContextAddPath(context, line.CGPath);
CGContextDrawPath(context, kCGPathStroke);
}
@end
您可以使用它,例如使用 UIGraphicsBeginImageContext 创建图像上下文并使用 UIGraphicsGetCurrentContext() 检索上下文。
否则,您可能需要更改代码并将生成的路径分配给 CALayer,然后将其添加到 UIView。
希望这对您有所帮助。
关于ios - 在一组给定点之间绘制贝塞尔曲线,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12904767/