绘制油漆后添加橡皮擦工具

Question

我有油漆应用程序。当我点击按钮它启动油漆视图比用户可以油漆。我回来后，然后点击按钮，画图不会重置。我如何重置一个视图在按钮点击后绘制痛苦。

代码:

- (BOOL) initContext:(CGSize)size {
    int bitmapByteCount;
    int bitmapBytesPerRow;
    // Declare the number of bytes per row. Each pixel in the bitmap in this
    // example is represented by 4 bytes; 8 bits each of red, green, blue, and
    // alpha.
    bitmapBytesPerRow = (size.width * 4);
    bitmapByteCount = (bitmapBytesPerRow * size.height);
    // Allocate memory for image data. This is the destination in memory
    // where any drawing to the bitmap context will be rendered.
    cacheBitmap = malloc( bitmapByteCount );
    if (cacheBitmap == NULL){
        return NO;
    }
    cacheContext = CGBitmapContextCreate (cacheBitmap, size.width, size.height, 8, bitmapBytesPerRow, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaNoneSkipFirst);
    return YES;
}
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    [self drawToCache:touch];
    [self setNeedsDisplay];
}
- (void) drawToCache:(UITouch*)touch {
    hue += 0.005;
    if(hue > 1.0) hue = 0.0;
    UIColor *color = [UIColor colorWithHue:hue saturation:0.7 brightness:1.0 alpha:1.0];
    CGContextSetStrokeColorWithColor(cacheContext, [color CGColor]);
    CGContextSetLineCap(cacheContext, kCGLineCapRound);
    CGContextSetLineWidth(cacheContext, 15);
    CGPoint lastPoint = [touch previousLocationInView:self];
    CGPoint newPoint = [touch locationInView:self];
    CGContextMoveToPoint(cacheContext, lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(cacheContext, newPoint.x, newPoint.y);
    CGContextStrokePath(cacheContext);
    CGRect dirtyPoint1 = CGRectMake(lastPoint.x-10, lastPoint.y-10, 20, 20);
    CGRect dirtyPoint2 = CGRectMake(newPoint.x-10, newPoint.y-10, 20, 20);
    [self setNeedsDisplayInRect:CGRectUnion(dirtyPoint1, dirtyPoint2)];
}


// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
    // Drawing code
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGImageRef cacheImage = CGBitmapContextCreateImage(cacheContext);
    CGContextDrawImage(context, self.bounds, cacheImage);
    CGImageRelease(cacheImage);

}

在视图控制器代码中:

 PaintView *paint = [[PaintView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:paint];
    [paint release];

Answer 1

in touchesmoved…为橡皮擦设置一个开关，并按如下方式更改代码:

if(togleEraser == NO)
{
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 1.0);
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x,         currentPoint.y);
}
else
{
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 20);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1, 0, 0, 10);
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextClearRect (UIGraphicsGetCurrentContext(), CGRectMake(lastPoint.x, lastPoint.y, 50, 50));
}