[Insight-users] Multiresolution turns my images into black images: PNG 16 bits

[Luis Ibanez]

Hi Adolfo,

Your problem is totally unrelated to the
multiresolution pyramid.

What happens is that you are saving images as
PNG files with 16bits but those images have
a dynamic range of only 8 bits.  Since most
viewers do not normalize the images, the image
*looks* black on the screen even though the
information is in there.

You have several options

1) convert the output images to 8 bits
    before saving it, making sure that you
    declare the ImageFileWriter to be of
    type Image<unsigned char,2>

2) fill the 16bits dynamic range by using
    the RescaleIntensityImageFilter

3) Don't use PNG for saving the images but
    a format like MetaImage

4) For viewing images use the ImageViewer
    application available in
    InsightApplications/ImageViewer



Regards,


   Luis


----------------------------
Adolfo González Uzábal wrote:
> Hello everybody there!
> 
> I'm just starting working with the MultiresolutionPyramidFilter in ITK 1.4
> 
> I read a .png image, put it into a multiresolution pyramid, 
> update it and try to get written the output images.
> 
> But the images are totally black.
> 
> I've tried the following:
> .- Recover the input of the pyramid and get it written. 
> OK. I got the image as I had put it.
> .- Change the Schedule for resolutions. 
> OK. The output sizes changes accordingly to the new schedule.
> .- In the forum I've seen some advice from Ms.Ng, about pixel types. I've tried 
> with uchar, uint and float with no good results.
> 
> I suppose I've missed any step in the generation process.
> 
> You can find the main part of my source attached (I've leave out some try/catch 
> structs just to be clearer).
> 
> Any suggestion or advice will be truly appreciated.
> 
> Best wishes!
> Adolfo G.U.
> 
> -------------------------------------
> typedef unsigned char PixelType;
> const unsigned int Dimension = 2;
> const unsigned int numberOfLevels = 2;
> typedef itk::Image< PixelType, Dimension >    ImageType;
> 	
> typedef itk::ImageFileReader< ImageType >  ReaderType;
> typedef itk::ImageFileWriter< ImageType >  WriterType;
> typedef itk::PNGImageIO ImageIOPNGType;
> 	  
> ReaderType::Pointer reader = ReaderType::New();
> WriterType::Pointer writer = WriterType::New();
> ImageIOPNGType::Pointer pngIO = ImageIOPNGType::New();
> 	
> const char * inputFilename  = "./Files/Circle.png";
> const char * outputFilename = "./Files/outputOriginal.png";
> 	
> reader->SetImageIO(pngIO);
> reader->SetFileName( inputFilename  );
> 
> typedef itk::MultiResolutionPyramidImageFilter<
> 			ImageType,
> 			ImageType > FixedImagePyramidType;
> 	  
> FixedImagePyramidType::Pointer myPyramid = 
>                              FixedImagePyramidType::New();
> 
> myPyramid->SetNumberOfLevels(numberOfLevels );
> myPyramid->SetInput(reader->GetOutput() ); 
> myPyramid->Update();
> 
> writer->SetInput( myPyramid->GetInput(0) );
> writer->SetFileName( "./Files/inputExtracted.png" );
> writer->Update(); // here everything goes properly
> 	
> for (int i = 0; i < myPyramid->GetNumberOfOutputs(); i++)
> {
> char tempFilename[50];
> sprintf( tempFilename, "./Files/outputResolution%d.png", i );
> 	
> writer->SetInput( myPyramid->GetOutput(i) );
> writer->SetFileName( tempFilename);
> writer->Update(); // ...but there I got only black images
> }
> 
>