uiimageview 上的透明度应显示图像 [重复]答案

【问题标题】：transparency on uiimageview should show image [duplicate]uiimageview 上的透明度应显示图像 [重复]
【发布时间】：2012-09-08 10:01:00
【问题描述】：

可能重复：
How to draw a transparent stroke (or anyway clear part of an image) on the iPhone

我有一个透明层的 uiimage 视图如果我们触摸那个透明层，应该擦除部分透明层并显示它的背面..我该怎么做....？提前致谢

【问题讨论】：

What have you tried?
UIImage * backgroundImage = [UIImage imageNamed:@"images.jpeg"]; CALayer* aLayer = [CALayer 层]; CGFloat nativeWidth = CGImageGetWidth(backgroundImage.CGImage); CGFloat nativeHeight = CGImageGetHeight(backgroundImage.CGImage); CGRect startFrame = CGRectMake(0.0, 0.0, nativeWidth, nativeHeight); aLayer.contents = (id)backgroundImage.CGImage; aLayer.frame = startFrame; [self.view.layer addSublayer:aLayer]; - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { ;
@pammu 你想从源图像中删除所选图像的位吗？
我有一个图像，上面有一个覆盖图像，当我删除覆盖时，它应该显示图像的一部分

标签： iphone objective-c uiimageview

【解决方案1】：

据我了解，您想通过触摸来擦除图像的一部分... 是对的吗？

试试这个代码，通过触摸移动部分图像来擦除......

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    lastTouch = [touch locationInView:canvasView];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    currentTouch = [touch locationInView:canvasView];

    CGFloat brushSize = 35;
    CGColorRef strokeColor = [UIColor whiteColor].CGColor;

    UIGraphicsBeginImageContext(scratchView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [canvasView.image drawInRect:CGRectMake(0, 0, canvasView.frame.size.width, canvasView.frame.size.height)];
    CGContextSetLineCap(context, kCGLineCapRound);
    CGContextSetLineWidth(context, brushSize);
    CGContextSetStrokeColorWithColor(context, strokeColor);
    CGContextSetBlendMode(context, kCGBlendModeClear);
    CGContextBeginPath(context);
    CGContextMoveToPoint(context, lastTouch.x, lastTouch.y);
    CGContextAddLineToPoint(context, currentTouch.x, currentTouch.y);
    CGContextStrokePath(context);
    canvasView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    lastTouch = [touch locationInView:canvasView];
}

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

}

希望对你有帮助....

【讨论】：