绘制油漆后添加橡皮擦工具答案

【问题标题】：Add eraser tool after draw paint绘制油漆后添加橡皮擦工具
【发布时间】：2013-04-03 11:43:23
【问题描述】：

我有绘画应用程序。当我单击按钮时，它会启动绘画视图，而不是用户可以绘画。在我回来然后单击按钮后，paintview 将不会重置。绘制疼痛后如何在按钮单击中重置视图。

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];

【问题讨论】：

最简单的方法是删除视图并重新创建它。
在您的问题中添加一些代码，您的问题不清楚...重置您的视图取决于您编写的让用户在该视图上绘画的代码

标签： iphone canvas uiview core-graphics paint

【解决方案1】：

触摸移动,,, 为橡皮擦做一个切换并更改代码如下。

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));
}

【讨论】：