iOS开发——刮奖

　　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