ITK/Examples/SimpleOperations/Transparency

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This example demonstrates how to assign transparency to pixels in an image. It then writes the result to a tif file for inspection and verification.

(I don't think QuickView can handle this example - the transparency would be lost).

Transparency.cxx

#include "itkImage.h"
#include "itkImageFileWriter.h"
#include "itkImageRegionIterator.h"
#include "itkTIFFImageIO.h"
#include "itkRGBAPixel.h"
 
int main(int argc, char *argv[])
{
  std::string outputFilename;
  if(argc > 1)
    {
    outputFilename = argv[1];
    }
  else
    {
    outputFilename = "test.tif";
    }
 
  typedef itk::RGBAPixel<unsigned char> PixelType;
  typedef itk::Image< PixelType, 2>  ImageType;
 
  ImageType::RegionType region;
  ImageType::IndexType start;
  start[0] = 0;
  start[1] = 0;
 
  ImageType::SizeType size;
  size[0] = 200;
  size[1] = 300;
 
  region.SetSize(size);
  region.SetIndex(start);
 
  ImageType::Pointer image = ImageType::New();
  image->SetRegions(region);
  image->Allocate();
 
  itk::ImageRegionIterator<ImageType> imageIterator(image,region);
 
  while(!imageIterator.IsAtEnd())
    {
    ImageType::PixelType pixel = imageIterator.Get();
 
    if(imageIterator.GetIndex()[0] > 100)
      {
      pixel.SetRed(0);
      pixel.SetGreen(255);
      pixel.SetBlue(0);
      //pixel.SetAlpha(255); // invisible
      pixel.SetAlpha(122);
      }
    else
      {
      pixel.SetRed(255);
      pixel.SetGreen(0);
      pixel.SetBlue(0);
      pixel.SetAlpha(0.5);
      }
    imageIterator.Set(pixel);
 
    ++imageIterator;
  }
 
  typedef  itk::ImageFileWriter< ImageType  > WriterType;
  typedef  itk::TIFFImageIO TIFFIOType;
  WriterType::Pointer writer = WriterType::New();
  TIFFIOType::Pointer tiffIO = TIFFIOType::New();
  tiffIO->SetPixelType(itk::ImageIOBase::RGBA);
  writer->SetFileName(outputFilename);
  writer->SetInput(image);
  writer->SetImageIO(tiffIO);
  writer->Update();
 
  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.9.5)
 
project(Transparency)
 
find_package(ITK REQUIRED)
include(${ITK_USE_FILE})
if (ITKVtkGlue_LOADED)
  find_package(VTK REQUIRED)
  include(${VTK_USE_FILE})
endif()
 
add_executable(Transparency MACOSX_BUNDLE Transparency.cxx)
 
if( "${ITK_VERSION_MAJOR}" LESS 4 )
  target_link_libraries(Transparency ITKReview ${ITK_LIBRARIES})
else( "${ITK_VERSION_MAJOR}" LESS 4 )
  target_link_libraries(Transparency ${ITK_LIBRARIES})
endif( "${ITK_VERSION_MAJOR}" LESS 4 )

Download and Build Transparency

Click here to download Transparency and its CMakeLists.txt file. Once the tarball Transparency.tar has been downloaded and extracted,

cd Transparency/build
  • If ITK is installed:
cmake ..
  • If ITK is not installed but compiled on your system, you will need to specify the path to your ITK build:
cmake -DITK_DIR:PATH=/home/me/itk_build ..

Build the project:

make

and run it:

./Transparency

WINDOWS USERS PLEASE NOTE: Be sure to add the ITK bin directory to your path. This will resolve the ITK dll's at run time.

Building All of the Examples

Many of the examples in the ITK Wiki Examples Collection require VTK. You can build all of the the examples by following these instructions. If you are a new VTK user, you may want to try the Superbuild which will build a proper ITK and VTK.

ItkVtkGlue

ITK >= 4

For examples that use QuickView (which depends on VTK), you must have built ITK with Module_ITKVtkGlue=ON.

ITK < 4

Some of the ITK Examples require VTK to display the images. If you download the entire ITK Wiki Examples Collection, the ItkVtkGlue directory will be included and configured. If you wish to just build a few examples, then you will need to download ItkVtkGlue and build it. When you run cmake it will ask you to specify the location of the ItkVtkGlue binary directory.