事实证明，在qt_mac_toQImage的Qt 5.15实现中使用的许多私有Qt内容适用于除了尝试对QImage进行CoreGraphics渲染之外的情况。一旦我将所有这些部分取出并简化，将CGImageRef转换为QImage或QPixmap的方法就相当简单了：

CGBitmapInfo CGBitmapInfoForQImage(const QImage &image)
{
    CGBitmapInfo bitmapInfo = kCGImageAlphaNone;
    
    switch (image.format()) {
        case QImage::Format_ARGB32:
            bitmapInfo = kCGImageAlphaFirst | kCGBitmapByteOrder32Host;
            break;
        case QImage::Format_RGB32:
            bitmapInfo = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host;
            break;
        case QImage::Format_RGBA8888_Premultiplied:
            bitmapInfo = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big;
            break;
        case QImage::Format_RGBA8888:
            bitmapInfo = kCGImageAlphaLast | kCGBitmapByteOrder32Big;
            break;
        case QImage::Format_RGBX8888:
            bitmapInfo = kCGImageAlphaNoneSkipLast | kCGBitmapByteOrder32Big;
            break;
        case QImage::Format_ARGB32_Premultiplied:
            bitmapInfo = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host;
            break;
        default:
            break;
    }
    
    return bitmapInfo;
}

QImage CGImageToQImage(CGImageRef cgImage)
{
    const size_t width = CGImageGetWidth(cgImage);
    const size_t height = CGImageGetHeight(cgImage);
    QImage image(width, height, QImage::Format_ARGB32_Premultiplied);
    image.fill(Qt::transparent);
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
    CGContextRef context = CGBitmapContextCreate((void *)image.bits(), image.width(), image.height(), 8,
                                                 image.bytesPerLine(), colorSpace, CGBitmapInfoForQImage(image));

    // Scale the context so that painting happens in device-independent pixels
    const qreal devicePixelRatio = image.devicePixelRatio();
    CGContextScaleCTM(context, devicePixelRatio, devicePixelRatio);
    
    CGRect rect = CGRectMake(0, 0, width, height);
    CGContextDrawImage(context, rect, cgImage);
    
    CFRelease(colorSpace);
    CFRelease(context);
    
    return image;
}

一旦您将CGImageRef转换为QImage，使用QPixmap::convertFromImage将其转换为QPixmap就很简单了。