如何将 UIImage 旋转 90 度？

我有一个UIImage那是UIImageOrientationUp（纵向）我想逆时针旋转 90 度（横向）。我不想使用CGAffineTransform。我想要的像素UIImage实际转移位置。我正在使用一段代码（如下所示），最初旨在调整UIImage去做这个。我将目标大小设置为当前大小UIImage但我收到错误：

（错误）：CGBitmapContextCreate：无效数据字节/行：对于 8 个整数位/组件、3 个组件、kCGImageAlphaPremultipliedLast，应至少为 1708。

（顺便说一句，每当我提供较小的尺寸作为目标尺寸时，我都不会收到错误）。我怎样才能旋转我的UIImage逆时针 90 度仅使用核心图形功能，同时保留当前尺寸？

-(UIImage*)reverseImageByScalingToSize:(CGSize)targetSize:(UIImage*)anImage
{
    UIImage* sourceImage = anImage; 
    CGFloat targetWidth = targetSize.height;
    CGFloat targetHeight = targetSize.width;

    CGImageRef imageRef = [sourceImage CGImage];
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);

    if (bitmapInfo == kCGImageAlphaNone) {
        bitmapInfo = kCGImageAlphaNoneSkipLast;
    }

    CGContextRef bitmap;

    if (sourceImage.imageOrientation == UIImageOrientationUp || sourceImage.imageOrientation == UIImageOrientationDown) {
        bitmap = CGBitmapContextCreate(NULL, targetHeight, targetWidth, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

    } else {


        bitmap = CGBitmapContextCreate(NULL, targetWidth, targetHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

    }       


    if (sourceImage.imageOrientation == UIImageOrientationRight) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -targetHeight);

    } else if (sourceImage.imageOrientation == UIImageOrientationLeft) {
        CGContextRotateCTM (bitmap, radians(-90));
        CGContextTranslateCTM (bitmap, -targetWidth, 0);

    } else if (sourceImage.imageOrientation == UIImageOrientationDown) {
        // NOTHING
    } else if (sourceImage.imageOrientation == UIImageOrientationUp) {
        CGContextRotateCTM (bitmap, radians(90));
        CGContextTranslateCTM (bitmap, 0, -targetHeight);
    }

    CGContextDrawImage(bitmap, CGRectMake(0, 0, targetWidth, targetHeight), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage* newImage = [UIImage imageWithCGImage:ref];

    CGContextRelease(bitmap);
    CGImageRelease(ref);

    return newImage; 
}

我相信最简单的方法（也是线程安全的）是：

//assume that the image is loaded in landscape mode from disk
UIImage * landscapeImage = [UIImage imageNamed:imgname];
UIImage * portraitImage = [[UIImage alloc] initWithCGImage: landscapeImage.CGImage
                                                     scale: 1.0
                                               orientation: UIImageOrientationRight];

注：如脑件说这只会修改图像的方向数据 - 像素数据不变。对于某些应用程序来说，这可能还不够。

或者用斯威夫特：

guard
    let landscapeImage = UIImage(named: "imgname"),
    let landscapeCGImage = landscapeImage.cgImage
else { return }
let portraitImage = UIImage(cgImage: landscapeCGImage, scale: landscapeImage.scale, orientation: .right)