Question

我正在尝试制作贴纸申请表。其中一项功能是擦除贴纸。

我能够擦除图像但是如何降低橡皮擦的强度呢？

目前在touchesMoved函数上，

我正在使用此代码：

UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:selectedFrame.imageView];

//erase part
UIGraphicsBeginImageContextWithOptions(selectedFrame.imageView.frame.size, NO, 0);
[selectedFrame.imageView.image drawInRect:CGRectMake(0, 0, selectedFrame.imageView.frame.size.width, selectedFrame.imageView.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(),5);
CGContextClearRect (UIGraphicsGetCurrentContext(), CGRectMake(lastPoint.x, lastPoint.y, 5, 5));
selectedFrame.imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;

这确实可以正确地擦除图像，但我想降低橡皮擦强度，因此它不会移除所有触摸的图像，但会略微降低图像的不透明度。附图如下：当前工作功能输出 - http://cloudart.com.au/projects/appscreenshots/Erased_image.png

所需的功能输出 - http://cloudart.com.au/projects/appscreenshots/app.png

基本上需要管理橡皮擦强度。任何帮助，将不胜感激。

Answer 1

代码中的2行可以更改您的橡皮擦大小

橡皮擦尺寸设置为5像素，在以下2行中进行任何更改，用给定行中的尺寸替换5。

CGContextSetLineWidth(UIGraphicsGetCurrentContext(),5);
CGContextClearRect (UIGraphicsGetCurrentContext(), CGRectMake(lastPoint.x, lastPoint.y, 5, 5));

Answer 2

感谢您的投入，但最终这对我有用 -

    UIGraphicsBeginImageContextWithOptions(selectedFrame.imageView.frame.size, NO, 0);
    [selectedFrame.imageView.image drawInRect:CGRectMake(0, 0, selectedFrame.imageView.frame.size.width, selectedFrame.imageView.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(),5);
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeDestinationOut);

    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 0.0, 0.0, 0.1);
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), YES);

    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    selectedFrame.imageView.image = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

Answer 3

UIGraphicsBeginImageContext(eraseimg1.frame.size);
[eraseimg1.image drawInRect:CGRectMake(0, 0,eraseimg1.frame.size.width, eraseimg1.frame.size.height)];

CGContextSetBlendMode(UIGraphicsGetCurrentContext( ),kCGBlendModeClear);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext( ), 50);
CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(), [[UIColor clearColor] CGColor]);

CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastTouch1.x, lastTouch1.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastTouch1.x, lastTouch1.y);

CGContextStrokePath(UIGraphicsGetCurrentContext()) ;
eraseimg1.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

擦除图像目标c上的功能

3 个答案: