CoreGpaphics

CoreGpaphics
CoreGpaphics基本应用

CGAffineTransformMake开头的函数是基于最初始的位置来变化的

带有CGAffineTransform参数是基于CGAffineTransform的位置变化的

CGAffineTransformIdentify就是原来没有变化前的位置

主要函数有:
```
CG_EXTERN const CGAffineTransform CGAffineTransformIdentity
  CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Return the transform [ a b c d tx ty ]. */

CG_EXTERN CGAffineTransform CGAffineTransformMake(CGFloat a, CGFloat b,
  CGFloat c, CGFloat d, CGFloat tx, CGFloat ty)
  CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Return a transform which translates by `(tx, ty)':
     t' = [ 1 0 0 1 tx ty ] */

CG_EXTERN CGAffineTransform CGAffineTransformMakeTranslation(CGFloat tx,
  CGFloat ty) CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Return a transform which scales by `(sx, sy)':
     t' = [ sx 0 0 sy 0 0 ] */

CG_EXTERN CGAffineTransform CGAffineTransformMakeScale(CGFloat sx, CGFloat sy)
  CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Return a transform which rotates by `angle' radians:
     t' = [ cos(angle) sin(angle) -sin(angle) cos(angle) 0 0 ] */

CG_EXTERN CGAffineTransform CGAffineTransformMakeRotation(CGFloat angle)
  CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Return true if `t' is the identity transform, false otherwise. */

CG_EXTERN bool CGAffineTransformIsIdentity(CGAffineTransform t)
  CG_AVAILABLE_STARTING(__MAC_10_4, __IPHONE_2_0);

/* Translate `t' by `(tx, ty)' and return the result:
     t' = [ 1 0 0 1 tx ty ] * t */

CG_EXTERN CGAffineTransform CGAffineTransformTranslate(CGAffineTransform t,
  CGFloat tx, CGFloat ty) CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Scale `t' by `(sx, sy)' and return the result:
     t' = [ sx 0 0 sy 0 0 ] * t */

CG_EXTERN CGAffineTransform CGAffineTransformScale(CGAffineTransform t,
  CGFloat sx, CGFloat sy) CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Rotate `t' by `angle' radians and return the result:
     t' =  [ cos(angle) sin(angle) -sin(angle) cos(angle) 0 0 ] * t */

CG_EXTERN CGAffineTransform CGAffineTransformRotate(CGAffineTransform t,
  CGFloat angle) CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

/* Invert `t' and return the result. If `t' has zero determinant, then `t'
   is returned unchanged. */

CG_EXTERN CGAffineTransform CGAffineTransformInvert(CGAffineTransform t)
  CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);
```
重写drawRect 只能写在所有视图的父类 UIView,

UIImageView等视图是不允许重写的

- (void)drawRect:(CGRect)rect

{

[super drawRect:rect];

UIBezierPath *bezierPath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(50, 50) radius:50 startAngle:0 endAngle:2 * M_PI clockwise:YES];

CAShapeLayer *caShapeLayer = [CAShapeLayer layer];

caShapeLayer.path = bezierPath.CGPath;

caShapeLayer.fillColor = [UIColor redColor].CGColor;

[self.layer addSublayer:caShapeLayer];





NSString *attrString =@"hellohellohellohellohellohellohellohellohello";

UIColor *stringColor = [UIColor colorWithRed:1.0 green:0.0f blue:0 alpha:1.0]; //设置文本的颜色

NSDictionary* attrs =@{NSForegroundColorAttributeName:stringColor,

   NSFontAttributeName:[UIFont fontWithName:@"AmericanTypewriter"size:18],

   }; //在词典中加入文本的颜色字体大小



[attrString drawInRect:CGRectMake(0,0,50,50)withAttributes:attrs]; //给文本限制个矩形边界，防止矩形拉伸；



NSString *s = @"我的小狗";

[s drawAtPoint:CGPointMake(100, 0) withFont:[UIFont systemFontOfSize:34.0]];



}
```
CGContextRef context= UIGraphicsGetCurrentContext();
    CGContextAddEllipseInRect(context, CGRectMake(10, 100, 300, 280));
    CGContextSetFillColorWithColor(context, [UIColor orangeColor].CGColor);
    CGContextFillPath(context);
    
    CGRect rectangle = CGRectMake(100, 290, 100, 25);
    CGContextAddRect(context, rectangle);
    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextFillPath(context);
    
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, 160, 220);
    CGContextAddLineToPoint(context, 190, 260);
    CGContextAddLineToPoint(context, 130, 260);
    CGContextClosePath(context);
    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextFillPath(context);
    
    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextAddArc(context, 120, 170, 25, 0 * M_PI, 2 * M_PI, YES);
    CGContextFillPath(context);
    
    CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
    CGContextAddArc(context, 200, 170, 25, 0 * M_PI, 2 * M_PI, YES);
    CGContextFillPath(context);
    
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, 160, 100);
    CGContextAddQuadCurveToPoint(context, 160, 50, 190, 50);
    CGContextSetLineCap(context, kCGLineCapSquare);
    CGContextSetLineWidth(context, 20);
    CGContextStrokePath(context);
    CGContextSetStrokeColorWithColor(context, [UIColor brownColor].CGColor);
    CGContextClosePath(context);
```
画图动画:
```
UIBezierPath *topBezierPath = [UIBezierPath bezierPath];
    [topBezierPath moveToPoint:CGPointMake(160, 100)];
    [topBezierPath addQuadCurveToPoint:CGPointMake(190,50) controlPoint:CGPointMake(160, 50)];
    topBezierPath.lineCapStyle = kCGLineCapSquare;
    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    shapeLayer.path = topBezierPath.CGPath;
    shapeLayer.fillColor = [UIColor clearColor].CGColor;
    shapeLayer.strokeColor = [UIColor brownColor].CGColor;
    shapeLayer.lineWidth = 20;
    
    CABasicAnimation *theAnimation;
    theAnimation=[CABasicAnimation animationWithKeyPath:@"strokeEnd"];
    theAnimation.delegate = self;
    theAnimation.duration = 2;
    theAnimation.removedOnCompletion = FALSE;
    theAnimation.fromValue = [NSNumber numberWithFloat:0];
    theAnimation.toValue = [NSNumber numberWithFloat:2];
    [shapeLayer addAnimation:theAnimation forKey:@"animateLayer"];
    
    [self.layer addSublayer:shapeLayer];
```
白板画图:

通过一个简单的画板（白板）来熟悉 Quartz 2D绘图

添加一个Empty Application,新建一个UIView类

在AppDelegate中修改代码：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{
    self.window = [[[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]] autorelease];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];

    //创建View，并指定View的大小为全屏
    WhiteBoardView *whiteView = [[WhiteBoardView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]];
    [self.window addSubview:whiteView];//把创建的View作为子视图加入窗口

    [whiteView release];

    [self.window makeKeyAndVisible];
    return YES;
}

修改UIView类中代码：

//  WhiteBoardView.h
//  DrawingBoard

#import <UIKit/UIKit.h>

@interface WhiteBoardView : UIView{

    CGContextRef whiteBoardContext;
    CGLayerRef    whiteBoardLayer;

}

@end

实现类：

//  WhiteBoardView.m
//  DrawingBoard

#import "WhiteBoardView.h"

@implementation WhiteBoardView

//对进行重写，以便在视图初始化的时候创建并设置自定义的Context
- (id)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame]) {

        self.backgroundColor = [UIColor whiteColor];//指定视图的背景色
        CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();    //指定色彩空间为RGB

        //创建Bitmap Context，大小为View自身的大小
        whiteBoardContext = CGBitmapContextCreate(NULL, self.frame.size.width, self.frame.size.height, 8,
                                                  4 *self.frame.size.width, colorSpace, kCGImageAlphaPremultipliedFirst);
        CGColorSpaceRelease(colorSpace) ;

        //创建新的CGLayer，用于画图
        whiteBoardLayer = CGLayerCreateWithContext(whiteBoardContext, self.frame.size, NULL);

        //得到新建层的Context
        CGContextRef layerContext  = CGLayerGetContext(whiteBoardLayer);

        //指定新建层Context的线宽
        CGContextSetLineWidth(layerContext, 1.5);
        CGContextSetLineCap(layerContext, kCGLineCapRound);    //指定线头形状为圆形
        CGContextSetRGBStrokeColor(layerContext, 0.0,0.0,0.0,1);//指定线的颜色，黑色

    }
    return self;
}

//对drawRect进行重写
- (void)drawRect:(CGRect)rect
{
    //先得到当前的Context
    CGContextRef currentContext = UIGraphicsGetCurrentContext();

    //根据Context的内容生成Bitmap
    CGImageRef image = CGBitmapContextCreateImage(whiteBoardContext);
    //把Bitmap绘制到Context上
    CGContextDrawImage(currentContext, [self bounds], image);
    //把whiteBoardLayer也绘到当前Context中
    CGContextDrawLayerInRect(currentContext    , [self bounds], whiteBoardLayer);

}

//屏幕触摸事件  触摸开始
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *theTouch = [touches anyObject];//先得到touch对象
    if ([theTouch tapCount] == 2)//判断是否为双击，是就清空图像
    {
        CGContextClearRect(whiteBoardContext, [self bounds]);//清空

        [self setNeedsDisplay];    //刷新屏幕显示
    }
    else//如果不是双击，就按手指划动处理，结果是画出一个点
    {
        [self touchesMoved:touches withEvent:event];
    }
}

//手指划动时画线的代码
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *theTouch = [touches anyObject];

    //得到当前位置
    CGPoint currentTouchLocation = [theTouch locationInView:self];
    //得到上次位置
    CGPoint lastTouchLoacation = [theTouch previousLocationInView:self];

    //取得Context
    CGContextRef layerContext = CGLayerGetContext(whiteBoardLayer);
    //开始定义Path
    CGContextBeginPath(layerContext);
    //把Path的起点移动到上次位置
    CGContextMoveToPoint(layerContext, lastTouchLoacation.x, lastTouchLoacation.y);
    //在上次位置和当前位置之间连线，并记入Path
    CGContextAddLineToPoint(layerContext, currentTouchLocation.x, currentTouchLocation.y);
    //沿Path画线
    CGContextStrokePath(layerContext);

    [self setNeedsDisplay];    //刷新屏幕

}

- (void)dealloc
{
    CGContextRelease(whiteBoardContext);
    CGLayerRelease(whiteBoardLayer);
    [super dealloc];
}

@end

3.OpenGL ES编程

一般是三个步骤：

（1）在Context中绘图

（2）把Context中的内容送入framebuffer

（3）显示framebuffer

二.CGPath的使用
CGContextRef contextRef = UIGraphicsGetCurrentContext();

CGPathMoveToPoint(mutablePathRef, NULL, 10, 10);
```
//(10, 10) 起点, (50, 100) 中点, (100, 10)终点
    CGPathAddCurveToPoint(mutablePathRef, NULL, 10, 10, 50, 100, 100, 10);
    CGContextAddPath(contextRef, mutablePathRef);
    CGContextSetStrokeColorWithColor(contextRef, [UIColor redColor].CGColor);
    CGContextSetLineWidth(contextRef, 2);
    CGContextDrawPath(contextRef, kCGPathFillStroke);
```
相关阅读:
vue 5 父子组件及组件间数据传递学习代码片段
 微信小程序设置数组对象的值
 微信小程序样式拼接类名三元运算以及条件拼接
 超简易消息通知滚动 pc移动适用
 js 批量监听-序号的闭包问题
 docker基础
 mysql
mongodb
django-restframework_认证
 SSM 整合
原文地址：https://www.cnblogs.com/apem/p/4342236.html

CoreGpaphics基本应用

CGAffineTransformMake开头的函数 是基于最初始的位置来变化的

带有CGAffineTransform参数是基于CGAffineTransform的位置变化的

CGAffineTransformIdentify就是原来没有变化前的位置

主要函数有:

画图动画:

白板画图:

CGAffineTransformMake开头的函数是基于最初始的位置来变化的