ios 在一组给定点之间绘制贝塞尔曲线

Drawing a bezier curve between a set of given points

提问by user462455

What is the best way to draw a bezier curve, in iOS application, that passes through a set of given points

在 iOS 应用程序中，通过一组给定点绘制贝塞尔曲线的最佳方法是什么

回答by mjrehder

A little more generic way to do it can be achieved by, for example, looking at the BEMSimpleLineGraph GitHub Project(see here for more info: bemsimplelinegraph). Here I extracted a method to draw a bezier curve through a given list of points.

例如，可以通过查看BEMSimpleLineGraph GitHub 项目（有关更多信息，请参见此处：bemsimplelinegraph）来实现更通用的方法。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。

The header file (BezierLine.h):

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

The implementation (BezierLine.m):

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

You can use it by for example creating an image context using UIGraphicsBeginImageContext and retrieving the context with UIGraphicsGetCurrentContext().

例如，您可以通过使用 UIGraphicsBeginImageContext 创建图像上下文并使用 UIGraphicsGetCurrentContext() 检索上下文来使用它。

Otherwise you may want to change the code and assign the resulting Path to a CALayer and add that to an UIView.

否则，您可能需要更改代码并将结果路径分配给 CALayer 并将其添加到 UIView。

Hope this helps.

希望这可以帮助。

回答by codingrhythm

I know this might be late, but just for anyone who is looking for the right answer. Instead of using addLineToPoint to draw the straight line. You can use addCurveToPoint to draw the curve. e.g.

我知道这可能为时已晚，但仅适用于正在寻找正确答案的任何人。而不是使用 addLineToPoint 来绘制直线。您可以使用 addCurveToPoint 来绘制曲线。例如

[bezierPath moveToPoint:CGPointMake(0, 0)];
[bezierPath addCurveToPoint:CGPointMake(40, 100) 
              controlPoint1:CGPointMake(20, 0) 
              controlPoint2:CGPointMake(20, 100)];
[bezierPath addCurveToPoint:CGPointMake(80, 50) 
              controlPoint1:CGPointMake(60, 100) 
              controlPoint2:CGPointMake(60, 50)];

// and you may don't want to close the path
// [bezierPath closePath];

It's really up to you to choose the control points of the curve. I just use the x = last_point_x + 20; y = last_point_y for control point one, and x = current_point_x - 20; y = current_point_y;

选择曲线的控制点完全取决于您。我只是使用 x = last_point_x + 20; y = last_point_y 控制点一，x = current_point_x - 20；y = current_point_y;

and you may want to use other value instead of the 20 as you may have different segment width of the curve.

并且您可能想要使用其他值而不是 20，因为您可能有不同的曲线段宽度。

回答by tiguero

You can easily google some example of how to create bezier curve on the web. I found this short tutas an example.

您可以轻松地在网上搜索一些有关如何创建贝塞尔曲线的示例。我发现这个简短的tut作为例子。

You can create a close bezier curve for e.g. with the following code snippet:

例如，您可以使用以下代码片段创建接近的贝塞尔曲线：

UIBezierPath* path = [UIBezierPath bezierPath];

[path moveToPoint:pt1];
[path addLineToPoint:pt2];
[path addLineToPoint:pt3];

[path closePath];

I hope it will help as a starting point.

我希望它会作为一个起点有所帮助。

回答by Milan Kamilya

Please try this.

请试试这个。

UIImageView *waterLevel = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,200,200)];
UIGraphicsBeginImageContext(waterLevel.frame.size);
[waterLevel.image drawAtPoint:CGPointZero];
//define BezierPath
UIBezierPath *bezierPath = [UIBezierPath bezierPath];


// Set the starting point of the shape.
[bezierPath moveToPoint:CGPointMake(0, 0)];

[bezierPath addLineToPoint:CGPointMake(waterLevel.frame.size.width, 0)];
[bezierPath addLineToPoint:CGPointMake(waterLevel.frame.size.width, waterLevel.frame.size.height)];
[bezierPath addLineToPoint:CGPointMake(0, waterLevel.frame.size.height)];
[bezierPath closePath];

bezierPath.lineWidth = 15;
//set the stoke color
[[UIColor blackColor] setStroke];
//draw the path
[bezierPath stroke];

// Add to the current Graphic context
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextAddPath(context,bezierPath.CGPath);
waterLevel.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

[self.view addSubview:waterLevel];

回答by fawrkes

You can be much more efficient by using the CGPointFromStringmethod:

使用以下CGPointFromString方法可以提高效率：

 NSArray *pointArray = @[@"{3.0,2.5}",@"{100.0,30.2}", @"{100.0,200.0}", @"{3.0,200.0}"];

// draw the path
UIBezierPath *aPath = [UIBezierPath bezierPath];
for (NSString *pointString in pointArray) {
    if ([pointArray indexOfObject:pointString] == 0)
        [aPath moveToPoint:CGPointFromString(pointString)];
    else
        [aPath addLineToPoint:CGPointFromString(pointString)];
}
[aPath closePath];

回答by Abdul

UIBezierPath *aPath = [UIBezierPath bezierPath];

// Set the starting point of the shape.
[aPath moveToPoint:CGPointMake(100.0, 0.0)];

// Draw the lines.
[aPath addLineToPoint:CGPointMake(200.0, 40.0)];
[aPath addLineToPoint:CGPointMake(160, 140)];
[aPath addLineToPoint:CGPointMake(40.0, 140)];
[aPath addLineToPoint:CGPointMake(0.0, 40.0)];
[aPath closePath];