[vtkusers] How to read and display a JPEG image

[Elvis Dowson]

Hi,
         I found out that I had to set the ColorWindow and ColorLevel  
to make the image appear as follows:

	// Map 2D image file
	imageMapper = vtkImageMapper::New();
		imageMapper->SetInput(imageReader->GetOutput());
		imageMapper->SetColorWindow(255);
		imageMapper->SetColorLevel(127.5);

Could someone please tell me why this is required? What is the effect  
of Color Window and Color Level on the image? I know that when it  
comes to medical imaging, with DICOM images there is a concept of  
window level and window width, used primarily for selectively  
displaying bone and tissue, but I don't know why you have Color Window  
and Color Level here for an image mapper.

Best regards,

Elvis Dowson

On Oct 3, 2008, at 8:02 PM, Elvis Dowson wrote:

> Hi,
>         I took a look at vtkActor2D, etc. The documentation is not  
> that helpful in figuring out what is going wrong. I think I have  
> used all the required methods in vtkActor2D, if you look at the code  
> below, such as using a JPEG reader, using an image mapper to prepare  
> the interface with vtkActor2D. But it still doesn't work.
>
> For the moment, I don't want to use vtkTextureActor2D, since I don't  
> want to mess around with scaling or altering the geometric  
> properties of the 2D map that I am importing. The underlying image  
> is a 2D map, so I want it to be preserved with it's original  
> properties.
>
> Could someone help me get this to work with vtkActor2D ?
>
> Best regards,
>
> Elvis
>
> 	// Declare object instance variables
> 	vtkJPEGReader* imageReader;
> 	vtkImageMapper* imageMapper;
> 	vtkActor2D* mapActor;		
> 	
> 	// Initialize objects
> 	imageReader = NULL;
> 	imageMapper = NULL;
> 	mapActor = NULL;
> 		
> 	// Read 2D image file
> 	imageReader = vtkJPEGReader::New();
> 		imageReader->SetFileName("/Users/elvis/Project/C4I/Source/cxx/ 
> vtkRendererMultiLayer/Dubai.A2003285.0655.250m.jpg");
> 		imageReader->Update();
> 	
> 	// Map 2D image file
> 	imageMapper = vtkImageMapper::New();
> 		imageMapper->SetInput(imageReader->GetOutput());	
>
> 	// Actor in scene
> 	mapActor = vtkActor2D::New();
> 		mapActor->SetLayerNumber(0);
> 		mapActor->SetMapper(imageMapper);			
>
> 	// Add Actor to renderer
> 	ren->AddActor2D(mapActor);

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