Imagemagick with greyscale images and 24 bit depth - imagemagick

Question

I am using the Imagick library to work with ImageMagick in PHP. I am first reading an (JPEG) image from an external server with:
$img = new Imagick();
$img->readImage($source);
And then upload it to my Amazon S3 bucket with the following code:
$s3 = new AmazonS3();
$s3->create_object(BUCKET, $destination_path, array(
'body' => $img->getImageBlob(),
'length' => $img->getImageSize(),
'acl' => AmazonS3::ACL_PUBLIC,
'contentType' => 'image/jpeg'
));
Everything seems to be working fine, the files appear in my storage bucket and I can view them in my browser. However, when handling greyscale images, ImageMagick converts the image from 24 bit depth to 8 bit depth. I would like them to keep their 24 bit depth, how could I achieve this? I've tried the following, without success:
$img->setImageType(imagick::IMGTYPE_TRUECOLOR);
For colorized images, everything works fine, images keep their 24 bit depth.
Edit:
It seems that ImageMagick changes the image type from 6 (truecolor) to 2 (greyscale). Trying to overwrite this does not work, as tested with the following code:
$img = new Imagick();
$img->readImage($source);
$img->setImageType(6);
echo $img->getImageType();
which outputs 2

Answer 1

Use setType() before you load the image. So:
$img = new Imagick();
$img->setType(6); //or use imagick::IMGTYPE_TRUECOLOR instead of 6
$img->loadImage($source);
This will output an image with truecolor, even if the loaded picture uses graycolors only.