擦除UIImageView

Question

如何通过在手指上滑动手指来擦除前面UIImage上的内容，并显示UIView背面的UIImage。

我在- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event中使用了以下代码来删除正面图像：

-(void)eraseDrawingContents
{
    UIGraphicsBeginImageContext(frontImage.frame.size);
    [frontImage.image drawInRect:CGRectMake(0, 0, frontImage.frame.size.width, frontImage.frame.size.height)];

    CGContextSaveGState(UIGraphicsGetCurrentContext());
    CGContextSetShouldAntialias(UIGraphicsGetCurrentContext(), YES);
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 25.0);
    CGContextSetShadowWithColor(UIGraphicsGetCurrentContext(), CGSizeMake(0, 0), 50, [[UIColor whiteColor]CGColor]);

    CGMutablePathRef path = CGPathCreateMutable();
    CGPathMoveToPoint(path, nil, lastPoint.x, lastPoint.y);
    CGPathAddLineToPoint(path, nil, currentPoint.x, currentPoint.y);
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(), kCGBlendModeClear);
    CGContextAddPath(UIGraphicsGetCurrentContext(), path);
    CGContextStrokePath(UIGraphicsGetCurrentContext());

    frontImage.image = UIGraphicsGetImageFromCurrentImageContext();
    CGContextRestoreGState(UIGraphicsGetCurrentContext());
    UIGraphicsEndImageContext();

    lastPoint = currentPoint;
}

我实现了以下输出。

但我需要像这样的输出。

我们如何实现此功能？

请帮帮我。

Answer 1

试试这个

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{


    UITouch *touch = [touches anyObject];
    CGPoint location = [touch locationInView:self.view];


   self.imgView.image = [self.imgView.image eraseImageAtPoint:location inImageView:self.imgView  fromEraser:eraserImg];



}



- (UIImage *)eraseImageAtPoint: (CGPoint)point inImageView: (UIImageView *)imgView fromEraser: (UIImage *)eraser
{
    UIGraphicsBeginImageContext(imgView.frame.size);

    [self drawInRect:CGRectMake(0, 0, imgView.frame.size.width, imgView.frame.size.height)];

    [eraser drawAtPoint:point blendMode:kCGBlendModeDestinationOut alpha:1.0];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return image;

}

并使用下面的图像作为橡皮擦，这将非常适合您。

此代码正在我的工作结果中给出以下结果：

Answer 2

您可以通过混合两个图像来实现此目的

下面有很多简单的方法，你也可以使用GPUImage ..

只需要将两个图像与所需的输出混合。

将两张图片相互混合..

混合更多你可以尝试

**kCGBlendModeOverlay,kCGBlendModeSoftLight,kCGBlendModeColorDodge,etc**

在 CGBlendMode 参数下面的函数..还有很多选项都有超过两个图像并合并..（即使使用直播相机也可以这样做）

-(UIImage *)blenimagwithimage:(NSString *)imagename mode:(CGBlendMode)kmode with:(float)opeticy
    {
        processedimage=nil;
        UIImage *inputImage;
        inputImage = [UIImage imageNamed:imagename];
        UIGraphicsBeginImageContext(originalImage.size);
        [originalImage drawInRect:CGRectMake(0.0, 0.0, originalImage.size.width, originalImage.size.height)];
        [inputImage drawInRect:CGRectMake(0.0, 0.0, originalImage.size.width, originalImage.size.height) blendMode:kmode alpha:opeticy];
        UIImage *layeredImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        return layeredImage;
    }

Answer 3

检查此sample code

它提供了这样的功能