Re: Problem with reading raw 16bit RGB data

On Mon, 9 Nov 2015, Manuel Koch wrote:

> I try to extract 16bit image from RAW camera image [1] using libraw.
>
> The output of libraw is described as 16bit plain bitmap of RGB values.
> See http://www.libraw.org/docs/API-CXX-eng.html#dcraw_make_mem_image.
>
> Somehow I’m unable to create an Magick::Image() instance of this extracted 16bit RGB bitmap data using the following code :
>
> // „image“ is a structure returned from libraw containing the data of the extracted image
> Magick::Blob blob( image->data, image->data_size ); // „data_size“ is 61011696
> Magick::Image img;
> img.size( Magick::Geometry(image->width,image->height) ); // „width“ is 3908, „height“ is 2602
> img.depth( image->bits ); // „bits“ is 16
> img.magick( "RGB" );
> img.read( blob );
>
> After read() the call to isValid() returns true.
> Saving this image to a file succeeds, but results in unrecognizable image waste !?

Since these are 16-bit values, the bytes in each value could be stored 
in big-endian or little-endian format.  GraphicsMagick likely defaults 
to big-endian.  If the data is in little-endian format (like x86 
Intel), then you should add a request for LSBEndian endianness.

For example

   img.endian(LSBEndian);

Bob
-- 
Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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