Which direction is `UIImageOrientationUp`

UIImage has a good property named imageOrientation, all the images taken by iPhone/iPad is stored in physical orientation, when draw it on the view, most of the UIKit API and CoreGraphic API can recognize the orientation and render it it correct orientation. But if you need to resize the image or do some effect on the image by yourself, you need to calculate the image orientation by yourself. Thus you MUST understand which direction is UIImageOrientationUp.

The possible orientations

The UIImage header file defined the orientations as:

typedef enum {
    UIImageOrientationUp,            // default orientation
    UIImageOrientationDown,          // 180 deg rotation
    UIImageOrientationLeft,          // 90 deg CCW
    UIImageOrientationRight,         // 90 deg CW
    UIImageOrientationUpMirrored,    // as above but image mirrored along other axis. horizontal flip
    UIImageOrientationDownMirrored,  // horizontal flip
    UIImageOrientationLeftMirrored,  // vertical flip
    UIImageOrientationRightMirrored, // vertical flip
} UIImageOrientation;

Fine, it is commented, but, hmm, no so well. Could you tell me which direction is the UIImageOrientationUp?

The UP orientation

It’s not the orientation when you hold your iPhone in the normal mode. Make a guess!

OK, I know your guys are not so patient, so,

Here is the correct answer: this orientation is the UP!

The UP orientation when you take a photo on iPhone

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