菜鸟教程——iOS UIKit绘制图像

iOS两大绘图框架：UIKit像UIImage、NSString（绘制文本）、UIBezierPath（绘制形状）、UIColor都知道如何绘制自己。 这些类提供了功能有限但使用方便的方法来让我们完成绘图任务。一般情况下，UIKit就是我们所需要的。 Core Graphics 这是一个绘图专用的API族，它经常被称为QuartZ或QuartZ2D。Core Graphics是iOS上所有绘图 功能的基石，包括UIKit。

本文主要介绍如何通过UIKit绘图。

1.drawRect:方法

-(void)drawRect:(CGRect)rect{

///绘制正方形路径

//    UIBezierPath * path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, 50, 50)];

///  绘制直径为50的圆

//    UIBezierPath * path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 50, 50)];

/// 绘制宽高为50，边角弧度为10的弧边矩形

//    UIBezierPath * path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, 50, 50) cornerRadius:10];

/// 绘大小为RoundedRect 的矩形，圆角切弧为cornerRadii    位置在UIRectCornerBottomRight

UIBezierPath * path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 10, 50, 50) byRoundingCorners:UIRectCornerBottomRight cornerRadii:CGSizeMake(10, 5)];

///绘制以（0，0）为圆心，半径为40，角度从0.2到0.5的圆弧，closewise为圆弧边是否封闭

//    UIBezierPath * path = [UIBezierPath bezierPathWithArcCenter:CGPointMake(0, 0) radius:40 startAngle:0.2 endAngle:0.5 clockwise:NO];

[[UIColor blueColor]setFill];

[path fill];

}

2.-(void)drawInContext:(CGContextRef)ctx；方法

（a）.自定义一个继承于CALayer类

@interface myLayer : CALayer

@end

@implementation myLayer

-(void)drawInContext:(CGContextRef)ctx{

UIGraphicsPushContext(ctx);

UIBezierPath  * path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(20, 20, 100, 150)];

[[UIColor greenColor]setFill];

[path fill];

UIGraphicsPopContext();

}

@end

（2）将自定义layer添加到主视图layer上

myLayer * layer = [myLayer layer];

layer.backgroundColor = [[UIColor redColor]CGColor];

layer.frame = CGRectMake(10, 100, 200,200);

[layer setNeedsDisplay];

[self.view.layer addSublayer:layer];

3.使用- (void)drawLayer:(CALayer*)layer inContext:(CGContextRef)ctx；

（1）.创建对象，实现绘图方法

@interface thridDrawLayerDelegate : NSObject

@end

@implementation thridDrawLayerDelegate

- (void)drawLayer:(CALayer*)layer inContext:(CGContextRef)ctx {

UIGraphicsPushContext(ctx);

UIBezierPath* p = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0,0,100,100)];

[[UIColor blueColor] setFill];

[p fill];

UIGraphicsPopContext();

}

（2）.添加到layer视图上

@interface ThridDrawViewController ()

{

CALayer * _layer;

thridDrawLayerDelegate *_layerDeleagete;

}

@end

@implementation ThridDrawViewController

- (void)viewDidLoad {

[super viewDidLoad];

self.view.backgroundColor = [UIColor whiteColor];

_layerDeleagete = [[thridDrawLayerDelegate alloc] init];

//1.创建自定义的layer

_layer=[CALayer layer];

//2.设置layer的属性

_layer.backgroundColor= [UIColor blackColor].CGColor;

_layer.frame=CGRectMake(100, 100, 200, 200);

_layer.delegate = _layerDeleagete;

[_layer setNeedsDisplay];

//3.添加layer

[self.view.layer addSublayer:_layer];

}

-(void)dealloc{

_layer.delegate = nil;

}

4.使用UIGraphicsBeginImageContextWithOptions生成图片；

UIGraphicsBeginImageContextWithOptions(CGSizeMake(200, 200), NO, 0);

UIBezierPath * path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(0, 0, 100, 100)];

[[UIColor greenColor] setFill];

[path fill];

UIImage * img = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

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