如何加载图像并根据它的方向 exif 数据旋转它并使用 UIImageOrientationUp exif 数据保存它

Question

如何加载图像并根据它的orientationexif数据进行旋转并使用UIImageOrientationUpexif数据（或没有任何方向exif数据）保存它，以便不处理exif方向数据的软件将正确显示图片？

Answer 1

加载图片就这么简单：

UIImage *image = [UIImage imageNamed:@"NameOfImageHere"];

或者如果你有图像数据：

NSData *imageData = [[NSData alloc] init];
UIImage *image = [UIImage imageWithData: imageData];

以下方法将帮助您使用UIImage中的exif数据修复方向

- (UIImage *)imageByFixingOrientation {

    UIImage *image = self;

    if (image.imageOrientation == UIImageOrientationUp) return image;

    CGAffineTransform transform = CGAffineTransformIdentity;

    switch (image.imageOrientation) {
        case UIImageOrientationDown:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, image.size.height);
            transform = CGAffineTransformRotate(transform, M_PI);
            break;

        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, 0);
            transform = CGAffineTransformRotate(transform, M_PI_2);
            break;

        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, 0, image.size.height);
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            break;
        case UIImageOrientationUp:
        case UIImageOrientationUpMirrored:
            break;
    }

    switch (image.imageOrientation) {
        case UIImageOrientationUpMirrored:
        case UIImageOrientationDownMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.width, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;

        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRightMirrored:
            transform = CGAffineTransformTranslate(transform, image.size.height, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
            break;
        case UIImageOrientationUp:
        case UIImageOrientationDown:
        case UIImageOrientationLeft:
        case UIImageOrientationRight:
            break;
    }

    // Now we draw the underlying CGImage into a new context, applying the transform
    // calculated above.
    CGContextRef ctx = CGBitmapContextCreate(NULL, image.size.width, image.size.height,
                                             CGImageGetBitsPerComponent(image.CGImage), 0,
                                             CGImageGetColorSpace(image.CGImage),
                                             CGImageGetBitmapInfo(image.CGImage));
    CGContextConcatCTM(ctx, transform);
    switch (image.imageOrientation) {
        case UIImageOrientationLeft:
        case UIImageOrientationLeftMirrored:
        case UIImageOrientationRight:
        case UIImageOrientationRightMirrored:
            CGContextDrawImage(ctx, CGRectMake(0,0,image.size.height,image.size.width), image.CGImage);
            break;

        default:
            CGContextDrawImage(ctx, CGRectMake(0,0,image.size.width,image.size.height), image.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);
    return img;
}

Answer 2

Swift 4 相当于我之前的 Objective-c 方法作为扩展：

extension UIImage {

    func byFixingOrientation(andResizingImageToNewSize newSize: CGSize? = nil) -> UIImage {

        guard let cgImage = self.cgImage else { return self }

        let orientation = self.imageOrientation
        guard orientation != .up else { return UIImage(cgImage: cgImage, scale: 1, orientation: .up) }

        var transform = CGAffineTransform.identity
        let size = newSize ?? self.size

        if (orientation == .down || orientation == .downMirrored) {
            transform = transform.translatedBy(x: size.width, y: size.height)
            transform = transform.rotated(by: .pi)
        }
        else if (orientation == .left || orientation == .leftMirrored) {
            transform = transform.translatedBy(x: size.width, y: 0)
            transform = transform.rotated(by: CGFloat.pi / 2)
        }
        else if (orientation == .right || orientation == .rightMirrored) {
            transform = transform.translatedBy(x: 0, y: size.height)
            transform = transform.rotated(by: -(CGFloat.pi / 2))
        }

        if (orientation == .upMirrored || orientation == .downMirrored) {
            transform = transform.translatedBy(x: size.width, y: 0);
            transform = transform.scaledBy(x: -1, y: 1)
        }
        else if (orientation == .leftMirrored || orientation == .rightMirrored) {
            transform = transform.translatedBy(x: size.height, y: 0)
            transform = transform.scaledBy(x: -1, y: 1)
        }

        // Now we draw the underlying CGImage into a new context, applying the transform calculated above.
        guard let ctx = CGContext(data: nil, width: Int(size.width), height: Int(size.height),
                                  bitsPerComponent: cgImage.bitsPerComponent, bytesPerRow: 0,
                                  space: cgImage.colorSpace!, bitmapInfo: cgImage.bitmapInfo.rawValue)
        else {
            return UIImage(cgImage: cgImage, scale: 1, orientation: orientation)
        }

        ctx.concatenate(transform)

        // Create a new UIImage from the drawing context
        switch (orientation) {
        case .left, .leftMirrored, .right, .rightMirrored:
            ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.height, height: size.width))
        default:
            ctx.draw(cgImage, in: CGRect(x: 0, y: 0, width: size.width, height: size.height))
        }

        return UIImage(cgImage: ctx.makeImage() ?? cgImage, scale: 1, orientation: .up)
    }
}

用法-1

let newImage = image.byFixingOrientation()

Usage-2（固定方向并将图像调整为新尺寸）

let newImage = image.byFixingOrientation(andResizingImageToNewSize: CGSize(width: 200, height: 200))