详解iOS App中图片的线段涂鸦功能

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

UIImageView *imageV = [[UIImageView alloc]initWithFrame:CGRectMake(10, 120, screen_Width-20, screen_Height-150)];
imageV.image = [UIImage imageNamed:@"640-960-1.jpg"];
[self.view addSubview:imageV];

UIButton *testBtn = [[UIButton alloc]initWithFrame:CGRectMake(screen_Width/2.0-60, 60, 120, 36)];
[testBtn setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
[testBtn setTitle:@"添加直线" forState:UIControlStateNormal];
[testBtn addTarget:self action:@selector(addLineAct:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:testBtn];
}

- (void)addLineAct:(id)sender{
NSLog(@"测试按钮");
}

@property(nonatomic,strong) NSMutableArray * completeLines; //已经画好的线条 存入数组
@property(nonatomic,strong) NSMutableDictionary* LinesInProscess; //正在画的线条 存入字典
@property(nonatomic,strong) UIColor *lineColor;//线条颜色
@property (nonatomic)float lineWidth;//线条的粗细

//初始化
- (id)initWithFrame:(CGRect)frame{
if (self = [super initWithFrame:frame]) {
//初始化变量
_completeLines = [[NSMutableArray alloc]init];
_LinesInProscess = [[NSMutableDictionary alloc]init];
//设置透明背景
self.backgroundColor = [UIColor clearColor];

}

return self;
}

#import
#import

@interface Line : NSObject

@property(nonatomic)CGPoint begin; //线条开始点

@property(nonatomic)CGPoint end; //线条结束点

@end

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
// Drawing code

//获取上下文
CGContextRef cgt=UIGraphicsGetCurrentContext();
//设置线条宽度
CGContextSetLineWidth(cgt, self.lineWidth);
//设置线条两端形状为圆角
CGContextSetLineCap(cgt, kCGLineCapRound);

//设置颜色
[self.lineColor set];
//绘制已经完成的线段
for (Line *line in _completeLines){
CGContextMoveToPoint(cgt, [line begin].x, [line begin].y);
CGContextAddLineToPoint(cgt, [line end].x, [line end].y );
CGContextStrokePath(cgt);
}


//绘制正在画的线段
for (NSArray *v in _LinesInProscess) {
Line *line =[_LinesInProscess objectForKey:v];
CGContextMoveToPoint(cgt, [line begin].x, [line begin].y);
CGContextAddLineToPoint(cgt, [line end].x, [line end].y );
CGContextStrokePath(cgt);
}

}

//清空画板
-(void)clearAll
{
[_completeLines removeLastObject];
[_LinesInProscess removeAllObjects];
[self setNeedsDisplay];
}


-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
//判断是否连按
for (UITouch *t in touches) {
if ([t tapCount]>1) {
//第二次画线时第一条线还未完成时结束画线
[self clearAll];
return;
}

//NSValue 作为键使用
NSValue *key=[NSValue valueWithNonretainedObject:t];

// 根据触摸位置创建Line对象
CGPoint loc=[t locationInView:self];
Line *newLine=[[Line alloc]init ];
newLine.begin=loc;
newLine.end=loc;
//将当前正在画的线存入字典
[_LinesInProscess setObject:newLine forKey:key];

}
}

-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
//手指移动过程中按照当前手指的位置动态更新线条
for (UITouch * t in touches) {
NSValue *key=[NSValue valueWithNonretainedObject:t];
// 找对象当前UITouch对象的Line对象
Line *line =[_LinesInProscess objectForKey:key];

CGPoint loc=[t locationInView:self];
line.end=loc;
}
[self setNeedsDisplay];
}

-(void)endTouches:(NSSet *) touches
{
//画线完成之后将当前线条加入_completeLines 数组中 同时删除字典_LinesInProscess里的线条
for (UITouch *t in touches) {
NSValue *key=[NSValue valueWithNonretainedObject:t];
Line *line =[_LinesInProscess objectForKey:key];
if (line) {
[_completeLines addObject:line];
[_LinesInProscess removeObjectForKey:key];
}
}
[self setNeedsDisplay];
}

-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[self endTouches:touches];
}

-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[self endTouches:touches];
}

- (void)addLineAct:(id)sender{
NSLog(@"测试按钮");

DrawLine *touchdrawView = [[DrawLine alloc]initWithFrame:imageV.frame];

touchdrawView.lineColor = [UIColor yellowColor];
touchdrawView.lineWidth = 5.0;
touchdrawView.tag = 902;
[self.view addSubview:touchdrawView];


}

//添加剪头
double r = sqrt((line.end.x-line.begin.x)*(line.end.x-line.begin.x)+(line.begin.y-line.end.y)*(line.begin.y-line.end.y));//线条长度
CGContextMoveToPoint(cgt,line.end.x,line.end.y);
//P1
CGContextAddLineToPoint(cgt,line.end.x-(10*(line.begin.y-line.end.y)/r),line.end.y-(10*(line.end.x-line.begin.x)/r));
//P3
CGContextAddLineToPoint(cgt,line.end.x+(20*(line.end.x-line.begin.x)/r), line.end.y-(20*(line.begin.y-line.end.y)/r));
//P2
CGContextAddLineToPoint(cgt,line.end.x+(10*(line.begin.y-line.end.y)/r),line.end.y+(10*(line.end.x-line.begin.x)/r));

CGContextAddLineToPoint(cgt, line.end.x,line.end.y);
CGContextDrawPath(cgt,kCGPathFillStroke);
CGContextStrokePath(cgt);