实例介绍
【实例截图】
【核心代码】
// // STScratchView.m // STScratchView // // Created by Sebastien Thiebaud on 12/17/12. // Copyright (c) 2012 Sebastien Thiebaud. All rights reserved. // #import "STScratchView.h" @implementation STScratchView - (id)initWithFrame:(CGRect)frame { self = [super initWithFrame:frame]; if (self) { [self setOpaque:NO]; _sizeBrush = 10.0; } return self; } #pragma mark - #pragma mark CoreGraphics methods // Will be called every touch and at the first init - (void)drawRect:(CGRect)rect { [super drawRect:rect]; UIImage *imageToDraw = [UIImage imageWithCGImage:scratchImage]; [imageToDraw drawInRect:CGRectMake(0.0, 0.0, self.frame.size.width, self.frame.size.height)]; } // Method to change the view which will be scratched - (void)setHideView:(UIView *)hideView { CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceGray(); int bitmapByteCount; int bitmapBytesPerRow; float scale = [UIScreen mainScreen].scale; UIGraphicsBeginImageContextWithOptions(hideView.bounds.size, NO, 0); [hideView.layer renderInContext:UIGraphicsGetCurrentContext()]; hideView.layer.contentsScale = scale; hideImage = UIGraphicsGetImageFromCurrentImageContext().CGImage; UIGraphicsEndImageContext(); size_t imageWidth = CGImageGetWidth(hideImage); size_t imageHeight = CGImageGetHeight(hideImage); bitmapBytesPerRow = (imageWidth * 4); bitmapByteCount = (bitmapBytesPerRow * imageHeight); CFMutableDataRef pixels = CFDataCreateMutable(NULL, imageWidth * imageHeight); contextMask = CGBitmapContextCreate(CFDataGetMutableBytePtr(pixels), imageWidth, imageHeight , 8, imageWidth, colorspace, kCGImageAlphaNone); CGDataProviderRef dataProvider = CGDataProviderCreateWithCFData(pixels); CGContextSetFillColorWithColor(contextMask, [UIColor blackColor].CGColor); CGContextFillRect(contextMask, self.frame); CGContextSetStrokeColorWithColor(contextMask, [UIColor whiteColor].CGColor); CGContextSetLineWidth(contextMask, _sizeBrush); CGContextSetLineCap(contextMask, kCGLineCapRound); CGImageRef mask = CGImageMaskCreate(imageWidth, imageHeight, 8, 8, imageWidth, dataProvider, nil, NO); scratchImage = CGImageCreateWithMask(hideImage, mask); CGImageRelease(mask); CGColorSpaceRelease(colorspace); } - (void)scratchTheViewFrom:(CGPoint)startPoint to:(CGPoint)endPoint { float scale = [UIScreen mainScreen].scale; 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]; } #pragma mark - #pragma mark Touch event - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesBegan:touches withEvent:event]; UITouch *touch = [[event touchesForView:self] anyObject]; currentTouchLocation = [touch locationInView:self]; } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesMoved:touches withEvent:event]; UITouch *touch = [[event touchesForView:self] anyObject]; if (!CGPointEqualToPoint(previousTouchLocation, CGPointZero)) { currentTouchLocation = [touch locationInView:self]; } previousTouchLocation = [touch previousLocationInView:self]; [self scratchTheViewFrom:previousTouchLocation to:currentTouchLocation]; } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesEnded:touches withEvent:event]; UITouch *touch = [[event touchesForView:self] anyObject]; if (!CGPointEqualToPoint(previousTouchLocation, CGPointZero)) { previousTouchLocation = [touch previousLocationInView:self]; [self scratchTheViewFrom:previousTouchLocation to:currentTouchLocation]; } } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesCancelled:touches withEvent:event]; } - (void)initScratch { currentTouchLocation = CGPointZero; previousTouchLocation = CGPointZero; } @end
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