画板（涂鸦）实现 - iOS

画板（涂鸦）实现

2017.3.7更新

• 不使用drawRect
• 内存消耗低 （把demo中XIB删除掉，内存大概在15M左右）

//橡皮擦
- (void)setEraseBrush:(HBPath *)path{
    
    UIGraphicsBeginImageContextWithOptions(self.frame.size, false, 0);
    
    [self.drawImage.image drawInRect:self.bounds];
    
    [[UIColor clearColor] set];
    
    path.bezierPath.lineWidth = _lineWidth;
    
    [path.bezierPath strokeWithBlendMode:kCGBlendModeClear alpha:1.0];
    
    [path.bezierPath stroke];
    
    self.drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
}

需求

• 更换画布背景（获取 拍照 或者 相册 的图像）
• 具有拍照 截屏保存功能
• 不同的画笔颜色，线宽
• 具有撤销 返回 清屏 擦除功能

思路

主要分三大块

• 背景
• 画布
• 画笔的功能界面

1.首先获取用户触摸事件开始

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    CGPoint point = [self getTouchSet:touches];

    HBPath *path = [HBPath pathToPoint:point pathWidth:_lineWidth isEraser:self.ise];

    path.pathColor = _lineColor;
    
    path.imagePath = [NSString stringWithFormat:@"%@.png",[self getTimeString]];
    
    [self.paths addObject:path];

    [self.tempPoints addObject:[HBDrawPoint drawPoint:point]];
    
    if ([self.delegate respondsToSelector:@selector(drawBoard:drawingStatus:model:)]) {
        [self.delegate drawBoard:self drawingStatus:HBDrawingStatusBegin model:nil];
    }
}

HBPath封装的NSObject对象

paths：装有HBPath对象

#pragma mark - HBPath
@interface HBPath : NSObject

@property (nonatomic, strong) UIColor *pathColor;//画笔颜色
@property (nonatomic, assign) CGFloat lineWidth;//线宽
@property (nonatomic, assign) BOOL isEraser;//橡皮擦
@property (nonatomic, assign) HBDrawingShapeType shapType;//绘制样式
@property (nonatomic, copy) NSString *imagePath;//图片路径
@property (nonatomic, strong) UIBezierPath *bezierPath;


+ (instancetype)pathToPoint:(CGPoint)beginPoint pathWidth:(CGFloat)pathWidth isEraser:(BOOL)isEraser;//初始化对象
- (void)pathLineToPoint:(CGPoint)movePoint WithType:(HBDrawingShapeType)shapeType;//画

@end

2.移动

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{

    CGPoint point = [self getTouchSet:touches];

    HBPath *path = [self.paths lastObject];
    
    [path pathLineToPoint:point WithType:self.shapType];
    
    if (self.ise) {
        [self setEraseBrush:path];
    }else{
        [self.drawView setBrush:path];
    }
    
    [self.tempPoints addObject:[HBDrawPoint drawPoint:point]];
    
    if ([self.delegate respondsToSelector:@selector(drawBoard:drawingStatus:model:)]) {
        [self.delegate drawBoard:self drawingStatus:HBDrawingStatusMove model:nil];
    }
}

3.结束

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self touchesMoved:touches withEvent:event];
    
    HBPath *path = [self.paths lastObject];
    
    UIImage *image = [self screenshot:self.drawImage];
    
    self.drawImage.image = image;
    
    [self.drawView setBrush:nil];
    
    NSData *imageData = UIImagePNGRepresentation(image);//UIImageJPEGRepresentation(image, 0.4);
    
    NSString *filePath = [ThumbnailPath stringByAppendingPathComponent:path.imagePath];

    BOOL isSave = [NSFileManager hb_saveData:imageData filePath:filePath];
    
    if (isSave) {
        
        NSLog(@"%@", [NSString stringWithFormat:@"保存成功: %@",filePath]);
    }
    HBDrawModel *model = [[HBDrawModel alloc] init];
    model.paintColor = [_lineColor toColorString];
    model.paintSize = @(_lineWidth);
    model.isEraser = [NSNumber numberWithBool:path.isEraser];
    model.pointList = self.tempPoints;
    model.shapType = [NSNumber numberWithInteger:self.shapType];
    
    if ([self.delegate respondsToSelector:@selector(drawBoard:drawingStatus:model:)]) {
        [self.delegate drawBoard:self drawingStatus:HBDrawingStatusEnd model:model];
    }

    //清空
    [self.tempPoints removeAllObjects];

}

其中HBDrawModel对象的作用是：操作结束后传递给外界操作的参数

拥有以下属性：

/**所有点的集合***/
@property (nonatomic, strong) NSArray * pointList;
/**画笔的颜色***/
@property (nonatomic, copy) NSString * paintColor;
/**背景图片***/
@property (nonatomic, copy) NSString * background;
/**动作 （返回 前进 画 改变背景 清屏）默认是 Action_playing ***/
@property (nonatomic, copy) NSString * action;
/**画笔大小***/
@property (nonatomic, strong) NSNumber * paintSize;
/**设备分辨率 宽***/
@property (nonatomic, strong) NSNumber * width;
/**设备分辨率 高***/
@property (nonatomic, strong) NSNumber * hight;
/**是不是橡皮擦***/
@property (nonatomic, strong) NSNumber * isEraser;

4.绘制

- (void)setBrush:(HBPath *)path
{
    CAShapeLayer *shapeLayer = (CAShapeLayer *)self.layer;
    
    shapeLayer.strokeColor = path.pathColor.CGColor;
    shapeLayer.fillColor = [UIColor clearColor].CGColor;
    shapeLayer.lineJoin = kCALineJoinRound;
    shapeLayer.lineCap = kCALineCapRound;
    shapeLayer.lineWidth = path.bezierPath.lineWidth;
    ((CAShapeLayer *)self.layer).path = path.bezierPath.CGPath;
    
    
}

最后强调一下关于橡皮擦的注意点！

和绘制线是一样的，区别在于绘制的时候加上下面这句代码。

if (self.isEraser)
[self.bezierPath strokeWithBlendMode:kCGBlendModeClear alpha:1.0];
更新->在最上面

真正的擦除你已经画的线，跟你画布的背景是不是白色，或者其他颜色没有关系！如果你的背景是图片，设置画笔的颜色与画布的颜色一致，就不会奏效了。

当然除了上面是使用贝塞尔路径绘制以外，你也可以使用上下文去实现，找准这个属性。妈妈再也不用担心橡皮擦啦~~~

问题

当两个设备中，一端正在画，另一端绘制对方画的线。如果对方先慢画，后快画。怎么在另一端也绘制出这种速度感？？
如您知道的话，希望在评论中可以给我一些思路。

解决

在这里感谢 @柯拉Sir @梦的森林 提供的思路。最新的代码已经更新，需要的朋友自取哈。

如果这个文章帮到了你，一定给我Star哦！

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