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,self.view.frame.size.width,self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(),kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(),10);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),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,self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(),kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(),10);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(),1.0);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(),lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(),currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
- (IBAction)clear:(id)sender {
drawImage.image = nil;
}
解决方法
好的,这就是我为橡皮擦工具所做的：
我添加这行代码：
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeClear);
我添加这行代码：
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeClear);
所以代码将是这样的东西：
- (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,self.view.frame.size.height)];
// I add this
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeClear);
CGContextSetLineCap(UIGraphicsGetCurrentContext(),sizeSlider.value);
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeClear);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(),currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
