iOS开发——刮奖

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　　还是直接上代码，有什么问题的话，直接评论。

　　1.在YYTScratchView.h文件中

//

//  YYTScratchView.h

//  Demo-刮奖

//

//  Created by yyt on 16/4/20.

//  Copyright © 2016年 yyt. All rights reserved.

//

#import <UIKit/UIKit.h>

@interface YYTScratchView : UIView

@property (nonatomic,assign) float sizeBrush;

-(void)setHideView:(UIView*) hideView;

@end

　　2在YYTScratchView.m文件中

//

//  YYTScratchView.m

//  Demo-刮奖

//

//  Created by yyt on 16/4/20.

//  Copyright © 2016年 yyt. All rights reserved.

//

#import "YYTScratchView.h"

@interface YYTScratchView (){

    CGContextRef _contextMask;//maskContext 用户touch 改变的context

    CGImageRef _scratchCGImg;//CGimageRef 封装_contextMask 图片信息 _contextMask改变 跟着改变 直到 调用生成UIImage

    CGPoint currPonit;

    CGPoint prePoint;

}

@end

@implementation YYTScratchView

- (id)initWithFrame:(CGRect)frame

{

    self = [super initWithFrame:frame];

    if (self) {

        [self setOpaque:NO];

        //设置透明 如果不透明就没法看到下一层了

        self.sizeBrush=10.0f;

    }

    return self;

}

- (void)drawRect:(CGRect)rect

{

    [super drawRect:rect];

    UIImage* imageToDraw=[UIImage imageWithCGImage:_scratchCGImg];

    [imageToDraw drawInRect:self.frame];

}

//setSizeBrush before setHideView

-(void)setHideView:(UIView*) hideView{

    CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceGray();

    CGFloat scale = [UIScreen mainScreen].scale;

    //获得当前传入View的CGImage

    UIGraphicsBeginImageContextWithOptions(hideView.bounds.size, NO, 0);

    hideView.layer.contentsScale=scale;

    [hideView.layer renderInContext:UIGraphicsGetCurrentContext()];

    CGImageRef hideCGImg=UIGraphicsGetImageFromCurrentImageContext().CGImage;

    UIGraphicsEndImageContext();

    //绘制Bitmap掩码

    size_t width=CGImageGetWidth(hideCGImg);

    size_t height=CGImageGetHeight(hideCGImg);

    CFMutableDataRef pixels;

    pixels=CFDataCreateMutable(NULL, width*height);

    //创建一个可变的dataRef 用于bitmap存储记录

    _contextMask = CGBitmapContextCreate(CFDataGetMutableBytePtr(pixels), width, height , 8, width, colorSpace, kCGImageAlphaNone);

    //数据提供者

    CGDataProviderRef dataProvider=CGDataProviderCreateWithCFData(pixels);

    //填充黑色背景 mask中黑色范围为显示内容 白色为不显示

    CGContextSetFillColorWithColor(_contextMask, [UIColor blackColor].CGColor);

    CGContextFillRect(_contextMask, self.frame);

    CGContextSetStrokeColorWithColor(_contextMask, [UIColor whiteColor].CGColor);

    CGContextSetLineWidth(_contextMask, self.sizeBrush);

    CGContextSetLineCap(_contextMask, kCGLineCapRound);

    CGImageRef mask=CGImageMaskCreate(width, height, 8, 8, width, dataProvider, nil, NO);

    _scratchCGImg=CGImageCreateWithMask(hideCGImg, mask);

    CGImageRelease(mask);

    CGColorSpaceRelease(colorSpace);

}

-(void)scratchViewFrom:(CGPoint)startPoint toEnd:(CGPoint)endPoint{

    float scale=[UIScreen mainScreen].scale;

    //CG的Y与UI的是反的 UI的y0在左上角 CG在左下

    CGContextMoveToPoint(_contextMask, startPoint.x*scale, (self.frame.size.height-startPoint.y)*scale);

    CGContextAddLineToPoint(_contextMask, endPoint.x*scale,(self.frame.size.height-endPoint.y)*scale);

    CGContextStrokePath(_contextMask);

    [self setNeedsDisplay];

}

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

    [super touchesBegan:touches withEvent:event];

}

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

    [super touchesMoved:touches withEvent:event];

    UITouch *touch=[touches anyObject];

    currPonit=[touch locationInView:self];

    prePoint=[touch previousLocationInView:self];

    [self scratchViewFrom:prePoint toEnd:currPonit];

}

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

    [super touchesEnded:touches withEvent:event];

    UITouch *touch=[touches anyObject];

    currPonit=[touch locationInView:self];

    prePoint=[touch previousLocationInView:self];

    [self scratchViewFrom:prePoint toEnd:currPonit];

}

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

    [super touchesCancelled:touches withEvent:event];

}

@end

　　3.在需要调用的地方

//

//  ViewController.m

//  Demo-刮奖

//

//  Created by yyt on 16/4/20.

//  Copyright © 2016年 yyt. All rights reserved.

//

#import "ViewController.h"

#import "YYTScratchView.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];

    imageView.image = [UIImage imageNamed:@"11.png"];

    [self.view addSubview:imageView];

    UIImageView *imageView2 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];

    imageView2.image = [UIImage imageNamed:@"22.png"];

    //[self.view addSubview:imageView];

    YYTScratchView *scratchView = [[YYTScratchView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];

    scratchView.sizeBrush = 20.0;

    [scratchView setHideView:imageView2];

    [self.view addSubview:scratchView];

}

@end

iOS开发——刮奖

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原文地址：http://www.cnblogs.com/yyt-hehe-yyt/p/5415699.html