ios - 使用 PanGestureRecognizer 裁剪 UIImageView 内 UIImage 的右侧

Question

我正在尝试“裁剪”imageView 内的图像。裁剪的含义:如果用户向左平移，则图片将从右侧向左侧裁剪。因此，当用户平移到右侧时，图片将完全显示，如果用户平移到最左侧，图片将不可见。

我尝试了以下方法:

@IBAction func handlePanGesture(recognizer: UIPanGestureRecognizer) {
    let translation = recognizer.translationInView(containerView)

    // Resize the image View
    let image = imageView.image!
    let hasAlpha = false
    let scale: CGFloat = 0.0

    let newRect = CGRectMake(0, 0, image.size.width - translation.x, image.size.height)
    UIGraphicsBeginImageContextWithOptions(newRect.size, !hasAlpha, scale)
    image.drawAtPoint(CGPointMake(-newRect.origin.x, -newRect.origin.y))
    let croppedImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    imageView.image = croppedImage

    recognizer.setTranslation(CGPointZero, inView: containerView)
}

这样的作品。查看 gif here (目前这仅适用于左图像)。

有人能指出我正确的方向吗？为什么图像高度不保持不变，是因为 contentMode 设置为“Aspect Fit”吗？为什么只有向左平移时才调整大小？ Here is a screenshot imageView的配置

感谢您的任何提示。

Answer 1

我按照以下方式解决了它。

我将解释并发布下面的代码。首先，我调整了图像大小以适合 imageView。这样我就可以将 contentMode 设置为 .Left。其次，我保留了该图像的两份副本。因此，一张图片可以从右向左裁剪，一张图片可以在用户从左向右平移时反转。 我上面的裁剪功能不起作用，所以我用 CGImageCreateWithImageInRect(_:_:) 裁剪它们。

这是适合我的 UIPanGestureRecognizer 代码:

@IBAction func handlePanGesture(recognizer: UIPanGestureRecognizer) {
    let translation = recognizer.translationInView(containerView)
    let imageLeft = googleImageView.image!
    let imageRef = CGImageCreateCopy(initiallyScaledImage?.CGImage)
    let imageRight = UIImage(CGImage: imageRef!, scale: (initiallyScaledImage?.scale)!, orientation: (initiallyScaledImage?.imageOrientation)!)

    if translation.x < 0 {
        let scale = imageLeft.scale
        let newRect = CGRectMake(0, 0, (imageLeft.size.width + translation.x) * scale, imageLeft.size.height * scale)
        let imageRef = CGImageCreateWithImageInRect(imageLeft.CGImage, newRect)

        if let croppedImage = imageRef {
            googleImageView.image = UIImage(CGImage: croppedImage, scale: scale, orientation: imageLeft.imageOrientation)
        }
    } else if translation.x > 0 {
        // Get the rect from above, add translation, set new picture
        let scale = imageRight.scale
        let newRect = CGRectMake(0, 0, (imageLeft.size.width + translation.x) * scale, imageRight.size.height * scale)
        let imageRef = CGImageCreateWithImageInRect(imageRight.CGImage, newRect)

        if let uncroppedImage = imageRef {
            googleImageView.image = UIImage(CGImage: uncroppedImage, scale: scale, orientation: imageRight.imageOrientation)
        }
    }

    recognizer.setTranslation(CGPointZero, inView: containerView)
}