UIImageOrientation到CIDetectorImageOrientation

Question

使用CIDetector来检测图像中的人脸，你需要根据文档指定图像方向，这意味着它与UIImageOrientation不同。谷歌为我找到了下面的功能，我试了试，但发现它似乎不正确，或者我可能遗漏了其他东西，因为有时方向是关闭的。有人知道是怎么回事吗？似乎一张照片从iDevice导出，然后导入到另一个iDevice，方向信息就会丢失/更改，从而导致一些方向不匹配。

- (int) metadataOrientationForUIImageOrientation:(UIImageOrientation)orientation
{
    switch (orientation) {
        case UIImageOrientationUp: // the picture was taken with the home button is placed right
            return 1;
        case UIImageOrientationRight: // bottom (portrait)
            return 6;
        case UIImageOrientationDown: // left
            return 3;
        case UIImageOrientationLeft: // top
            return 8;
        default:
            return 1;
    }
}

Answer 1

为了涵盖它们，并且不使用幻数赋值( CGImagePropertyOrientation的原始值可能会在未来发生变化，但这不太可能……这仍然是一个很好的实践)您应该包含ImageIO框架并使用实际的常量：

#import <ImageIO/ImageIO.h>
- (CGImagePropertyOrientation)CGImagePropertyOrientation:(UIImageOrientation)orientation
{
    switch (orientation) {
        case UIImageOrientationUp:
            return kCGImagePropertyOrientationUp;
        case UIImageOrientationUpMirrored:
            return kCGImagePropertyOrientationUpMirrored;
        case UIImageOrientationDown:
            return kCGImagePropertyOrientationDown;
        case UIImageOrientationDownMirrored:
            return kCGImagePropertyOrientationDownMirrored;
        case UIImageOrientationLeftMirrored:
            return kCGImagePropertyOrientationLeftMirrored;
        case UIImageOrientationRight:
            return kCGImagePropertyOrientationRight;
        case UIImageOrientationRightMirrored:
            return kCGImagePropertyOrientationRightMirrored;
        case UIImageOrientationLeft:
            return kCGImagePropertyOrientationLeft;
    }
}

Answer 2

在Swift 4中

func inferOrientation(image: UIImage) -> CGImagePropertyOrientation {
  switch image.imageOrientation {
  case .up:
    return CGImagePropertyOrientation.up
  case .upMirrored:
    return CGImagePropertyOrientation.upMirrored
  case .down:
    return CGImagePropertyOrientation.down
  case .downMirrored:
    return CGImagePropertyOrientation.downMirrored
  case .left:
    return CGImagePropertyOrientation.left
  case .leftMirrored:
    return CGImagePropertyOrientation.leftMirrored
  case .right:
    return CGImagePropertyOrientation.right
  case .rightMirrored:
    return CGImagePropertyOrientation.rightMirrored
  }
}

Answer 3

Swift 4：

func convertImageOrientation(orientation: UIImageOrientation) -> CGImagePropertyOrientation  {
    let cgiOrientations : [ CGImagePropertyOrientation ] = [
        .up, .down, .left, .right, .upMirrored, .downMirrored, .leftMirrored, .rightMirrored
    ]

    return cgiOrientations[orientation.rawValue]
}