[Insight-users] how can I convert the image type

[Zachary Pincus]

Hello,

Displaying 16-bit (i.e. "unsigned short") greyscale files causes some 
viewers trouble -- especially PNG files (which are more rarely seen in 
the 16-bit variety.)

First, try adjusting the brightness/contrast in your viewer. It might 
be that the useful values of your image are all in the 8-bit range, and 
the viewer did not automatically scale the image properly. (Looking at 
an image with pixels in the range 0-255 when the viewer is trying to 
show some scaled version of all the values from 0-65535 generally 
produces screen output that looks "black.")

Alternately, it might be that your PNG viewer just breaks totally on 
16-bit files... this happens with some viewers. You could try saving 
the output as a TIFF and using a program that's good at reading 16-bit 
TIFFs (The Adobe Photoshop family is works, if you have access to it. 
The ImageMagick "display" tool, if you've got a UNIX-ish system, is 
also good.)

Finally, just try reading and writing the images as 8-bit for your 
test. All viewers deal with 8-bit images fine. This would involve 
changing the following:
>  typedef unsigned short PixelType;
to
>  typedef unsigned char PixelType;

Also, note that in general you do not have to explicitly set the 
writer's IO type (e.g. the "pngIO") -- it is usually automatically 
detected from the file name you set.

Zach Pincus

Department of Biochemistry and Program in Biomedical Informatics
Stanford University School of Medicine



On Jul 1, 2004, at 12:03 AM, Guorong Wu wrote:

> hello:
>      I want to convert one type of image to another type, for example, 
> I will convert RatLungSlice1.mha to RatLungSlice.png. I write a simple 
> program as follows but it doesn't work. The output is all black. I 
> guess it is wrong to simply link the imagefilereader and 
> imagefilewriter without doing anything. Can you tell me what work I 
> should do or which section I shuold refer to the document of  
> ITKSoftwareGuide? Thanks.
>
> #include "itkImageFileReader.h"
> #include "itkImageFileWriter.h"
> #include "itkImage.h"
> #include "itkPNGImageIO.h"
> main(int argc, char **argv)
> {
> 	typedef unsigned short PixelType;
> 	const unsigned int Dimension=2;
> 	typedef itk::Image<PixelType, Dimension> ImageType;
> 	typedef itk::ImageFileReader<ImageType> ReaderType;
> 	typedef itk::ImageFileWriter<ImageType> WriterType;
> 	typedef itk::PNGImageIO ImageIOType;
> 	ReaderType::Pointer reader=ReaderType::New();
> 	WriterType::Pointer writer=WriterType::New();
> 	ImageIOType::Pointer pngIO=ImageIOType::New();
> 	//const char *InputFilename=argv[1];
> 	//const char *OutputFilename=argv[2];
> 	reader->SetFileName("RatLungSlice1.mha);
> 	writer->SetFileName("RatLungSlice1.png");
> 	writer->SetInput(reader->GetOutput());
> 	writer->SetImageIO(pngIO);
> 	writer->Update();
> 	return 0;
>
> }
>  				
>
> 　　　　　　　　Guorong Wu
> 　　　　　　　　grwu at sjtu.edu.cn
> 　　　　　　　　　　2004-07-01
>
> =============================================================
> Guorong Wu	
> The Department of Computer Science and Technology
> Shanghai Jiao Tong University
> 1954 Huashan RD
> Shanghai China
> 200030
> Tel:  +86 21 3226 1236  , 6293 2089
> =============================================================
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