Question

我正在创建一个绘图应用程序，我想知道如何实现橡皮擦工具。我不想让我的橡皮擦工具绘制白色，因为我想让用户更改背景颜色。而且，是否可以设定刷子的硬度？如果是，请告诉我如何。

谢谢

这是我到目前为止所做的：

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    lastPoint = [touch locationInView:self.view];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    CGPoint currentPoint = [touch locationInView:self.view];
    UIGraphicsBeginImageContext(self.view.frame.size);
    [drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 10);
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 1.0);
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    lastPoint = currentPoint;
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 10);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 1.0);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

lastPoint = currentPoint;
}
- (IBAction)clear:(id)sender {
drawImage.image = nil;
}

Answer 1

好的，这就是我为橡皮擦工具所做的事情：
我添加这行代码：
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);

所以代码将是这样的：

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];

// I add this
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);

CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), sizeSlider.value);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);

CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}

Answer 2

我已经制作了涂料应用程序，它可以在iTunes“Easy Doodle”应用程序上找到。橡皮擦没有特殊的逻辑。只需获取背景图像的RGB值并将其传递给

CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),R value,G value,B value, 1.0);

根据所选的背景图片。

Answer 3

好的，所以我一直在寻找一个如何创建橡皮擦一周的解决方案，我不得不改变我看待它的方式因为无论我多少次尝试擦除它会消除背景图像也是。

然而，最后我找到了一个适合我的解决方案（在那里我可以擦除油漆并且仍然感觉背景图像没有被触及或擦除）并且希望它能帮助其他人。所以这里......

1）在UIView中创建2个图像视图 2）使用您想要的背景图像设置两个图像视图... 3）我创建了一个分段控件来确定用户是否想要擦除 4）选择分段控制时添加以下功能..

  func drawLineForRubber(fromPoint: CGPoint, toPoint: CGPoint) {

    // 1
    UIGraphicsBeginImageContext(view.frame.size)
    let context = UIGraphicsGetCurrentContext()
    mainImageView.image?.drawInRect(CGRect(x: 0, y: 0, width: view.frame.size.width, height: view.frame.size.height))

    // 2
    CGContextMoveToPoint(context, fromPoint.x, fromPoint.y)
    CGContextAddLineToPoint(context, toPoint.x, toPoint.y)

    // 3
    CGContextSetBlendMode(context, CGBlendMode.Clear)
    CGContextSetLineCap(context, CGLineCap.Round)
    CGContextSetLineWidth(context, 10.0)
    //this line is very important as it paints the screen clear
    CGContextSetRGBStrokeColor(context, red, green, blue, 0.0)
    CGContextSetBlendMode(context, CGBlendMode.Clear)

    // 4
    CGContextStrokePath(context)

    // 5
    mainImageView.image = UIGraphicsGetImageFromCurrentImageContext()
    mainImageView.alpha = opacity
    UIGraphicsEndImageContext()

}

正如您将看到有一条线将CGContextSetRGBStrokeColor设置为值0.0，这是重要的原因，当用户正在擦除绘画时，他正在从顶部imageview中删除油漆透明的颜色。但是，由于在其下方有另一个图像视图，因此感觉看起来就像是在不影响背景图像的情况下被擦掉。

相反它被擦掉了，但背后的图像视图，使它看起来像它没有。当您想要导出图像时（您可以通过多种方式进行操作，但我使用了以下内容）您已使用背景图像进行绘制，只需将两个图像视图组合为第一个imageview将有你画的油漆和第二个imageview将具有您想要的原始背景图像。

    func share() {

    let layer = UIApplication.sharedApplication().keyWindow!.layer
    let scale = UIScreen.mainScreen().scale
    UIGraphicsBeginImageContextWithOptions(layer.frame.size, false, scale); // reconsider size property for your screenshot

    layer.renderInContext(UIGraphicsGetCurrentContext()!)
    let screenshot = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()


    UIGraphicsBeginImageContext(mainImageView.bounds.size)
    mainImageView.image?.drawInRect(CGRect(x: 0, y: 0,
        width: mainImageView.frame.size.width, height: mainImageView.frame.size.height))

    UIGraphicsEndImageContext()

    let activity = UIActivityViewController(activityItems: [screenshot], applicationActivities: nil)
    presentViewController(activity, animated: true, completion: nil)
}

希望这有助于其他人一路走来......男人花了我很多时间来解决它=）

在iOS中为paint应用程序制作橡皮擦工具

3 个答案: