当我们使用相机拍照后，调用UIImagePickerController的delegate方法，如下代码所示：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];

}

通过UIImagePickerControllerOriginalImage这个key从info字典中可以获取到拍照后的UIImage，但如果断点查看图片，我们会发现图片是旋转了90度的。

不过如果直接使用图片，比如使用这个UIImage赋值给一个UIImageView的实例，显示出来的图片是完全没有问题的。

但如果使用这个UIImage作他用，比如上传到服务器，就会出现问题了，上传到服务器的图片也是旋转了90度的。

原因：通过UIImagePickerControllerOriginalImage这个key从info字典中可以获取到拍照后的UIImage，其imageOrientation属性默认是UIImageOrientationRight，也就是说默认就是向左侧旋转了90度的。

解决方法如下:

方法一：创建UIImagePickerController实例的时候，设置实例的一个属性allowsEditing为YES，设了这个值，拍完照片后会在照片上出现一个框框，可以对照片的裁剪编辑。在UIImagePickerController的代理方法中取照片的时候也就别用UIImagePickerControllerOriginalImage这个key来取了，而要用UIImagePickerControllerEditedImage，此时取出来的照片，它的imageOrientation是UIImageOrientationUp而不是默认的UIImageOrientationRight了。

方法二：有一个专门针对UIImage旋转这个问题的很好的Category，代码如下：

OC版本：

UIImage+fixOrientation.h

#import

@interface UIImage (fixOrientation)
- (UIImage *)fixOrientation;
@end

UIImage+fixOrientation.m

#import "UIImage+fixOrientation.h"

@implementation UIImage (fixOrientation)

- (UIImage *)fixOrientation {

    // No-op if the orientation is already correct
    if(self.imageOrientation == UIImageOrientationUp)returnself;

    // We need to calculate the proper transformation to make the image upright.
    // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
    CGAffineTransform transform = CGAffineTransformIdentity;

    switch(self.imageOrientation) {
    caseUIImageOrientationDown:
    caseUIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform,self.size.width,self.size.height);
        transform = CGAffineTransformRotate(transform, M_PI);
        break;
    caseUIImageOrientationLeft:
    caseUIImageOrientationLeftMirrored:
        transform = CGAffineTransformTranslate(transform,self.size.width,0);
        transform = CGAffineTransformRotate(transform, M_PI_2);
        break;
    caseUIImageOrientationRight:
    caseUIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform,0,self.size.height);
        transform = CGAffineTransformRotate(transform, -M_PI_2);
        break;
    }

    switch(self.imageOrientation) {
    caseUIImageOrientationUpMirrored:
    caseUIImageOrientationDownMirrored:
        transform = CGAffineTransformTranslate(transform,self.size.width,0);
        transform = CGAffineTransformScale(transform,-1,1);
        break;

    caseUIImageOrientationLeftMirrored:
    caseUIImageOrientationRightMirrored:
        transform = CGAffineTransformTranslate(transform,self.size.height,0);
        transform = CGAffineTransformScale(transform,-1,1);
        break;
    }

    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.
    CGContextRef ctx = CGBitmapContextCreate(NULL,self.size.width,self.size.height,
                                             CGImageGetBitsPerComponent(self.CGImage),0,
                                             CGImageGetColorSpace(self.CGImage),
                                             CGImageGetBitmapInfo(self.CGImage));
    CGContextConcatCTM(ctx, transform);
    switch(self.imageOrientation) {
    caseUIImageOrientationLeft:
    caseUIImageOrientationLeftMirrored:
    caseUIImageOrientationRight:
    caseUIImageOrientationRightMirrored:
        // Grr...
        CGContextDrawImage(ctx, CGRectMake(0,0,self.size.height,self.size.width),self.CGImage);
        break;

    default:
        CGContextDrawImage(ctx, CGRectMake(0,0,self.size.width,self.size.height),self.CGImage);
        break;
    }

    // And now we just create a new UIImage from the drawing context
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    UIImage *img = [UIImage imageWithCGImage:cgimg];
    CGContextRelease(ctx);
    CGImageRelease(cgimg);
    returnimg;
}
@end

Swift版本：

#importUIKit

extension UIImage {
    // 修复图片旋转
    funcfixOrientation() ->UIImage{
        if self.imageOrientation == .up{
            returnself
        }
        vartransform =CGAffineTransform.identity

        switch self.imageOrientation {
        case .down, .downMirrored:
            transform = transform.translatedBy(x:self.size.width, y:self.size.height)
            transform = transform.rotated(by: .pi)
            break

        case .left, .leftMirrored:
            transform = transform.translatedBy(x:self.size.width, y:0)
            transform = transform.rotated(by: .pi/2)
            break

        case .right, .rightMirrored:
            transform = transform.translatedBy(x:0, y:self.size.height)
            transform = transform.rotated(by: -.pi/2)
            break

        default:
            break
        }

        switch self.imageOrientation {
        case .upMirrored, .downMirrored:
            transform = transform.translatedBy(x:self.size.width, y:0)
            transform = transform.scaledBy(x:-1, y:1)
            break

        case .leftMirrored, .rightMirrored:
            transform = transform.translatedBy(x:self.size.height, y:0);
            transform = transform.scaledBy(x:-1, y:1)
            break
        default:
            break
        }

        letctx =CGContext(data:nil, width:Int(self.size.width), height:Int(self.size.height), bitsPerComponent:self.cgImage!.bitsPerComponent, bytesPerRow:0, space:self.cgImage!.colorSpace!, bitmapInfo:self.cgImage!.bitmapInfo.rawValue)
        ctx?.concatenate(transform)

        switch self.imageOrientation {
        case .left, .leftMirrored, .right, .rightMirrored:
            ctx?.draw(self.cgImage!, in:CGRect(x:CGFloat(0), y:CGFloat(0), width:CGFloat(size.height), height:CGFloat(size.width)))
            break

        default:
            ctx?.draw(self.cgImage!, in:CGRect(x:CGFloat(0), y:CGFloat(0), width:CGFloat(size.width), height:CGFloat(size.height)))
            break
        }

        letcgimg:CGImage = (ctx?.makeImage())!
        letimg = UIImage(cgImage: cgimg)

        return img
    }
}