在开始之前,我们需要创建一个DrawRectView
其初始代码为
//
// DrawRectView.h
// CGContextSetShouldAntialias
//
// Created by YouXianMing on 2017/8/30.
// Copyright © 2017年 TechCode. All rights reserved.
// #import <UIKit/UIKit.h> @interface DrawRectView : UIView @end
//
// DrawRectView.m
// CGContextSetShouldAntialias
//
// Created by YouXianMing on 2017/8/30.
// Copyright © 2017年 TechCode. All rights reserved.
// #import "DrawRectView.h" @implementation DrawRectView - (instancetype)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { self.backgroundColor = [UIColor clearColor];
self.layer.borderWidth = 0.5f;
self.layer.borderColor = [UIColor redColor].CGColor;
} return self;
} @end
在ViewController中使用(尺寸为100x100并居中)
显示效果如下(用红色边框显示边界)
修改DrawRectView.m代码如下
//
// DrawRectView.m
// CGContextSetShouldAntialias
//
// Created by YouXianMing on 2017/8/30.
// Copyright © 2017年 TechCode. All rights reserved.
// #import "DrawRectView.h" @implementation DrawRectView - (instancetype)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { self.backgroundColor = [UIColor clearColor];
self.layer.borderWidth = 0.5f;
self.layer.borderColor = [UIColor redColor].CGColor;
} return self;
} - (void)drawRect:(CGRect)rect { // Set stroke color
[[UIColor blackColor] setStroke]; // Draw 7 lines.
for (int i = ; i < ; i++) { UIBezierPath *path = [UIBezierPath bezierPath];
path.lineWidth = 0.5f;
[path moveToPoint:CGPointMake(, + i * 10.3)];
[path addLineToPoint:CGPointMake( + , + i * 10.3)];
[path stroke];
}
} @end
其实就添加了下面的绘图代码而已,绘制7条线条,每条线条的宽度为0.5
效果如下
将图片放大后会发现,线条的宽度并不一致,有的颜色深,有的颜色浅,这就是开了抗锯齿之后的效果
修改代码关闭抗锯齿
//
// DrawRectView.m
// CGContextSetShouldAntialias
//
// Created by YouXianMing on 2017/8/30.
// Copyright © 2017年 TechCode. All rights reserved.
// #import "DrawRectView.h" @implementation DrawRectView - (instancetype)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { self.backgroundColor = [UIColor clearColor];
self.layer.borderWidth = 0.5f;
self.layer.borderColor = [UIColor redColor].CGColor;
} return self;
} - (void)drawRect:(CGRect)rect { // Get context.
CGContextRef context = UIGraphicsGetCurrentContext(); // Sets anti-aliasing on.
CGContextSetShouldAntialias(context, NO); // Set stroke color
[[UIColor blackColor] setStroke]; // Draw 7 lines.
for (int i = ; i < ; i++) { UIBezierPath *path = [UIBezierPath bezierPath];
path.lineWidth = 0.5f;
[path moveToPoint:CGPointMake(, + i * 10.3)];
[path addLineToPoint:CGPointMake( + , + i * 10.3)];
[path stroke];
}
} @end
显示效果
图片放大后,线条宽度一致
结论
开了抗锯齿后,系统会对绘制的线条进行一定的模糊处理,来达到不容易看到狗牙的目的,什么是狗牙?你可以运行以下代码来看看两者之间的区别
//
// DrawRectView.m
// CGContextSetShouldAntialias
//
// Created by YouXianMing on 2017/8/30.
// Copyright © 2017年 TechCode. All rights reserved.
// #import "DrawRectView.h" @implementation DrawRectView - (instancetype)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { self.backgroundColor = [UIColor clearColor];
self.layer.borderWidth = 0.5f;
self.layer.borderColor = [UIColor redColor].CGColor;
} return self;
} - (void)drawRect:(CGRect)rect { // Get context.
CGContextRef context = UIGraphicsGetCurrentContext(); // Sets anti-aliasing off.
CGContextSetShouldAntialias(context, NO); // Set stroke color
[[UIColor blackColor] setStroke]; // Draw 7 lines.
for (int i = ; i < ; i++) { UIBezierPath *path = [UIBezierPath bezierPath];
path.lineWidth = 0.5f;
[path moveToPoint:CGPointMake(, + i * 10.3)];
[path addLineToPoint:CGPointMake( + , + i * 10.3)];
[path stroke];
}
} @end
关闭抗锯齿后不会出现模糊现象,都会出现锯齿,俗称狗牙
打开抗锯齿功能之后线条会模糊,锯齿得到了一些缓解,称作抗锯齿
