ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController

//图片控件(画板)
@property (weak, nonatomic) IBOutlet UIImageView *imgView;

//起止点
@property (nonatomic,assign) CGPoint lineStartPoint;
@property (nonatomic,assign) CGPoint lineEndPoint;

//所有按钮和选中的按钮
@property (nonatomic,strong) NSMutableArray *buttonArray;
@property (nonatomic,strong) NSMutableArray *selectedButtons;

@property (nonatomic,assign) BOOL drawFlag;

@end

ViewController.m

#import "ViewController.h"


@implementation ViewController


#pragma mark- Class property
@synthesize drawFlag,imgView;
@synthesize lineStartPoint,lineEndPoint;
@synthesize buttonArray,selectedButtons;


#pragma mark-Global variables
NSArray *arrImgs = nil;


#pragma mark- Class method
/**
 *  视图加载
 */
- (void)viewDidLoad {
    [super viewDidLoad];

    //设置定位
    self.imgView.frame = self.view.frame;

    //背景图片数组
    arrImgs = [NSArray arrayWithObjects:@"bg_01.jpg",@"bg_02.jpg",@"bg_03.jpeg",
               @"bg_04.png",@"bg_05.jpg",@"bg_06.jpeg",@"bg_07.jpeg", nil];

    //加载按钮
    [self loadButtons];

    //随机设置背景图片
    [self ChangeBgImg];
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}


/**
 *  shouldAutorotate
 *  是否允许内容跟着屏幕切换而改变
 *
 *  @return Bool
 */
-(BOOL) shouldAutorotate{
    return NO;
}



/**
 *  加载按钮
 */
-(void) loadButtons{

    float w = 70;
    float h = 70;
    float x = 15;
    float y = 150;
    int space = 40;

    self.buttonArray = [[NSMutableArray alloc] init];
    for (int i = 0; i < 9; i++) {

        if ((i % 3 == 0) && i > 0) {
            //另起一行
            y += h + space;
            x = 15;
        }

        //添加按钮
        [self CreateButton:(i+1) x: x y:y h:h w:w];

        x += w + space;
    }

}


/**
 *  touchesBegan 触摸开始事件
 *
 *  @param touches touches description
 *  @param event   event description
 */
-(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{

    UITouch *touch = [touches anyObject];
    if (touch) {

        CGPoint touchPoint;
        for (UIButton *btn in self.buttonArray) {

            touchPoint = [touch locationInView:btn];
            if ([btn pointInside:touchPoint withEvent:nil]) {

                self.lineStartPoint = btn.center;
                self.drawFlag = YES;

                if (!self.selectedButtons)
                    self.selectedButtons = [NSMutableArray arrayWithCapacity:9];

                [self.selectedButtons addObject:btn];
            }
        }
    }

}


/**
 *  touchesMoved 一根或者多根手指在屏幕上移动
 *
 *  @param touches touches description
 *  @param event   event description
 */
-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{

    UITouch *touch =[touches anyObject];
    if (touch && self.drawFlag) {
        self.lineEndPoint = [touch locationInView:imgView];

        CGPoint touchPoint;
        BOOL btnContained;
        for (UIButton *btn in self.buttonArray) {

            touchPoint = [touch locationInView:btn];
            if ([btn pointInside:touchPoint withEvent:nil]) {
                btnContained = NO;

                for (UIButton *selectedBtn in self.selectedButtons) {
                    if (btn == selectedBtn) {
                        btnContained = YES;
                        break;
                    }
                }

                if (!btnContained)
                    [self.selectedButtons addObject:btn];

            }
        }

        //划线
        UIColor *color = [UIColor whiteColor];
        [self drawLineWithColor:color width:8.0f];
    }
}


/**
 *  touchesEnded 滑动手势结束
 *
 *  @param touches touches description
 *  @param event   event description
 */
-(void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{

    self.drawFlag = NO;
    self.selectedButtons = nil;

    //判断手势密码是否正确,……


}


/**
 *  drawLineWithColor 
 *  自定义划线功能
 *
 *  @param color      颜色
 *  @param width      宽度
 *  @param startPoint 开始位置
 *  @param endPoint   结束位置
 *
 *  @return UIImage
 */
-(void) drawLineWithColor:(UIColor *)color width:(CGFloat)width{

    CGPoint btnCenter;
    UIImage *image = nil;

    UIGraphicsBeginImageContext(self.imgView.frame.size);

    //一个不透明类型的Quartz 2D绘画环境,相当于一个画布,你可以在上面任意绘画
    CGContextRef context = UIGraphicsGetCurrentContext();

    //设置划线宽度和颜色
    CGContextSetLineWidth(context, width);
    CGContextSetStrokeColorWithColor(context, [color CGColor]);

    /**
     * CGLineCap
     *  kCGLineCapButt   //和第三个一样
     *  kCGLineCapRound  //端点是圆的
     *  kCGLineCapSquare //正方形
     */
    //设置线的端点形状
    CGContextSetLineCap(context, kCGLineCapRound);

    //设置线的起始位置
    CGContextMoveToPoint(context, self.lineStartPoint.x, self.lineStartPoint.y);

    //将选中的点连接起来
    for (UIButton *selectBtn in self.selectedButtons) {

        btnCenter = selectBtn.center;
        CGContextAddLineToPoint(context, btnCenter.x, btnCenter.y);
        CGContextMoveToPoint(context, btnCenter.x, btnCenter.y);
    }

    //结束位置
    CGContextAddLineToPoint(context, self.lineEndPoint.x, self.lineEndPoint.y);

    CGContextStrokePath(context);

    image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    //追加到画板
    self.imgView.image = image;
    image = nil;

}


/**
 *  CButton 自定义按钮
 *
 *  @param int   按钮的值
 *  @param float x
 *  @param float y
 *  @param float width
 *  @param float height
 *
 *  @return void
 */
-(void) CreateButton:(int) v x:(float) x y:(float) y h:(float) h w:(float) w{

    //初始化按钮
    UIButton *cbtn = [[UIButton alloc] init];

    //设置位置和尺寸
    cbtn.frame = CGRectMake(x, y, w, h);

    //设置按钮信息
    cbtn.userInteractionEnabled = NO;
    cbtn.tag = v;

    //设置字体颜色
    [cbtn setTitleColor:[UIColor whiteColor] forState:UIControlStateNormal];

    //设置背景颜色
    [cbtn setBackgroundColor:[UIColor clearColor]];

    //设置为圆形
    cbtn.layer.cornerRadius = 35;
    cbtn.layer.borderWidth = 3.5;
    cbtn.layer.borderColor = [UIColor whiteColor].CGColor;
    cbtn.clipsToBounds = TRUE;//去除边界

    //添加到当前视图
    [self.view addSubview:cbtn];

    //添加到数组
    [self.buttonArray addObject:cbtn];

    //释放
    cbtn = nil;
};


/**
 *  ChangeBgImg
 *  随机设置背景图片
 */
-(void) ChangeBgImg{

    //获取背景图片控件
    UIImageView *bgImgV = (UIImageView*)[self.view viewWithTag:11];

    if (bgImgV) {
        bgImgV.frame = self.view.frame;

        //获取随机索引
        int rd = 0 + (arc4random() % ([arrImgs count] - 1));
        NSString *strImgName = (NSString*)[arrImgs objectAtIndex:rd];

        bgImgV.image = [UIImage imageNamed:strImgName];
    }
}

@end