刮刮樂的可刮部份

//
//  ScratchableView.h
//  CGScratch
//
//  Created by Olivier Yiptong on 11-01-11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import <UIKit/UIKit.h>


@interface ScratchableView : UIView {
    float width;
    float height;
    CGPoint    location;
    CGPoint    previousLocation;
    BOOL firstTouch;
    CGImageRef scratchable;
    CGImageRef scratched;
    CGContextRef alphaPixels;
    CGDataProviderRef provider;
}

- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end;

@end

//
//  ScratchableView.m
//  CGScratch
//
//  Created by Olivier Yiptong on 11-01-11.
//  Copyright 2011 __MyCompanyName__. All rights reserved.
//

#import "ScratchableView.h"


@implementation ScratchableView


- (id)initWithFrame:(CGRect)frame {
   
    self = [super initWithFrame:frame];
    if (self) {
        //self.bounds = CGRectMake(0.0, 0.0, frame.size.width, frame.size.height);
       
        //自行把用來刮的scratch.png放入專案
        scratchable = [UIImage imageNamed:@"scratch.png"].CGImage;
//修改成隨bounds大小變化 by Harvey 20130903
//          width = CGImageGetWidth(scratchable);
//          height = CGImageGetHeight(scratchable);
        width = self.bounds.size.width;
        height = self.bounds.size.height;
        self.opaque = NO;
        CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceGray();
       
        CFMutableDataRef pixels = CFDataCreateMutable( NULL , width * height );
        alphaPixels = CGBitmapContextCreate( CFDataGetMutableBytePtr( pixels ) , width , height , 8 , width , colorspace , kCGImageAlphaNone );
        provider = CGDataProviderCreateWithCFData(pixels);
       
       
        CGContextSetFillColorWithColor(alphaPixels, [UIColor blackColor].CGColor);
        CGContextFillRect(alphaPixels, frame);
       
        CGContextSetStrokeColorWithColor(alphaPixels, [UIColor whiteColor].CGColor);
        CGContextSetLineWidth(alphaPixels, 20.0);
        CGContextSetLineCap(alphaPixels, kCGLineCapRound);
       
        //CGImageRef mask = CGImageMaskCreate(width, height, 8, 8, width, provider, nil, NO);
        CGImageRef mask = CGImageMaskCreate(width, height, 8, 8, width, provider, nil, NO);
        scratched = CGImageCreateWithMask(scratchable, mask);
       
        CGImageRelease(mask);
        CGColorSpaceRelease(colorspace);
       

    }
    return self;
}

- (void)drawRect:(CGRect)rect {
    CGContextDrawImage(UIGraphicsGetCurrentContext() , [self bounds] , scratched);
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event touchesForView:self] anyObject];
    firstTouch = YES;
    location = [touch locationInView:self];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event touchesForView:self] anyObject];
   
    if (firstTouch) {
        firstTouch = NO;
        previousLocation = [touch previousLocationInView:self];
    } else {
        location = [touch locationInView:self];
        previousLocation = [touch previousLocationInView:self];
    }
   
    // Render the stroke
    [self renderLineFromPoint:previousLocation toPoint:location];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [[event touchesForView:self] anyObject];
    if (firstTouch) {
        firstTouch = NO;
        previousLocation = [touch previousLocationInView:self];
       
        [self renderLineFromPoint:previousLocation toPoint:location];
    }
}

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

- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end {
   
    CGContextMoveToPoint(alphaPixels, start.x , start.y );
    CGContextAddLineToPoint(alphaPixels, end.x , end.y );
    CGContextStrokePath(alphaPixels);
    [self setNeedsDisplay];
}

- (void)dealloc {
    CGContextRelease(alphaPixels);
    CGImageRelease(scratchable);
    CGDataProviderRelease(provider);
    [super dealloc];
}


@end