Hello ImageDev

This first example, also presented in the Getting Started section of the Reference Guide, briefly introduces how to open an image from a file and apply two consecutive image processing algorithms on it.

The initial image is a grayscale image that appears almost totally gray when opened with a basic image viewer.

<b>Figure 1.</b> Default display of the initial image

Figure 1. Default display of the initial image

The reason of this aspect is the poor contrast of the image. Almost all pixel intensities are 128 or 129 which are basically displayed in a same neutral gray. A few sparse pixels have the value 0 (black) or 255 (white).

The first step of this example applies the RescaleIntensity algorithm in Percentile mode. This algorithm consists of expanding the image dynamics from two input values to the output range [0, 255].

The first input value is taken from the first intensity of the cumulated histogram representing at least 2% of all data. It falls on 128.
The second input value is taken from the first intensity of the cumulated histogram representing at least 98% of all data. It falls on 129.

Then, when applying the normalization, all pixels having an intensity lower than or equal to 128 are set to 0 and pixels having an intensity greater than or equal to 129 are set to 255.

You can notice that the syntax to invoke this first algorithm is the function mode. The algorithm is executed in a single instruction.

<b>Figure 2.</b> Result of the image normalization

Figure 2. Result of the image normalization

The magic happens and we can now read the text. The image still contains some salt noise which corresponds to the 255 values from the initial image.

To remove the white spots, the example applies a median filter which is an efficient filter for removing impulse noise.

The syntax used to apply this second algorithm is the class mode. The syntax change here serves the purpose of demonstrating the options of both class and function programming using ImageDev. This step also could be launched with a single instruction like in the previous step.

<b>Figure 3.</b> Final image after median filter denoising

Figure 3. Final image after median filter denoising

Notes:

In Python, the imshow method displays ImageDev images in a window. You can remove the comment symbol in front of each 'imagedev.imshow' instruction to visualize the result images.
This example also shows how to properly catch exceptions. The catch section is run when an error occurs in the try section. In this case the program ends properly with an error message instead of causing a crash. To force the program to pass inside the catch function you can:
- Rename or move the password.dat file to cause an exception when invoking the Init function.
- Change the intensityOutputRange of the rescaleIntensity methode to [10, 65535] to cause an inconstancy between the output range and the output type (8-bit).

#include <ImageDev/ImageDev.h>
#include <ioformat/IOFormat.h>
#include <iolink/view/ImageViewProvider.h>

using namespace imagedev;
using namespace ioformat;
using namespace iolink;

int
main()
{
    try
    {
        // ImageDev library initialization
        if ( imagedev::isInitialized() == false )
            imagedev::init();

        // Open a tif file
        auto imageInput = readImage( std::string( IMAGEDEVDATA_IMAGES_FOLDER ) + "hello_imagedev.tif" );

        // Apply a normalization of its graylevels using function coding style
        auto imageNorm = rescaleIntensity( imageInput,
                                           RescaleIntensity::OutputType::SAME_AS_INPUT,
                                           RescaleIntensity::RangeMode::PERCENTILE,
                                           { 2, 98 },
                                           { 0, 255 },
                                           { 0, 255 } );

        // Save the normalized image as a png file
        writeView( imageNorm, R"(T01_01_norm.png)" );

        // Apply a median filter processing using class coding style
        MedianFilter2d processMedian;
        processMedian.setInputImage( imageNorm );
        processMedian.setKernelMode( MedianFilter2d::KernelMode::DISK );
        processMedian.setKernelRadius( 1 );
        processMedian.execute();
        auto imageMedian = processMedian.outputImage();

        // Save the resulting image as a png file
        writeView( processMedian.outputImage(), R"(T01_01_output.png)" );

        // ImageDev library finalization
        imagedev::finish();
    }
    catch ( imagedev::Exception& error )
    {
        // Print potential exception in the standard output
        std::cerr << "HelloImageDev exception: " << error.what() << std::endl;
        return -1;
    }

    return 0;
}

using System;
using ImageDev;
using IOLink;
using IOFormat;

namespace T01_01_HelloImageDev
{
    class Program
    {
        static void Main( string[] args )
        {
            try
            {
                // Initialize the ImageDev library if not done
                if ( Initialization.IsInitialized() == false )
                    Initialization.Init();

                // Open a tif file
                ImageView imageInput = ViewIO.ReadImage( @"Data/images/hello_imagedev.tif" );

                // Apply a normalization of its graylevels using function coding style
                ImageView imageNorm = Processing.RescaleIntensity( imageInput,
                                                                   RescaleIntensity.OutputType.SAME_AS_INPUT,
                                                                   RescaleIntensity.RangeMode.PERCENTILE,
                                                                   new double[] { 2, 98 },
                                                                   new double[] { 0, 255 },
                                                                   new double[] { 10, 255 } );
                ViewIO.WriteView( imageNorm, @"T01_01_norm.png" );

                // Apply a median filter processing using class coding style
                MedianFilter2d processMedian = new MedianFilter2d {
                    inputImage = imageNorm,
                    kernelMode = MedianFilter2d.KernelMode.DISK,
                    kernelRadius = 1,
                };
                processMedian.Execute();
                var imageMedian = processMedian.outputImage;

                // Notify the garbage collector that the intermediate image can be freed
                imageNorm.Dispose();

                // Save the resulting image as a png file
                ViewIO.WriteView( imageMedian, @"T01_01_output.png" );

                // ImageDev library finalization
                Initialization.Finish();
            }
            catch ( Exception error )
            {
                // Print potential exception in the standard output
                System.Console.WriteLine("HelloImageDev exception: " + error.ToString() );
                System.Environment.Exit( -1 );
            }
        }
    }
}

import imagedev
import imagedev_data
import ioformat

try:
  # Initialize the ImageDev library if not done
  if (imagedev.is_initialized() == False): imagedev.init()

  # Open and display a tif file
  image_input = ioformat.read_image(imagedev_data.get_image_path("hello_imagedev.tif"))
  #imagedev.imshow(image_input, False)

  # Apply a normalization of its graylevels using function coding style
  image_norm = imagedev.rescale_intensity(image_input, range_mode=imagedev.RescaleIntensity.RangeMode.PERCENTILE)

  # Display and save the normalized image as a png file
  #imagedev.imshow(image_norm, False)
  ioformat.write_view(image_norm, "T01_01_norm.png")

  # Apply a median filter processing using class coding style
  process_median = imagedev.MedianFilter2d()
  process_median.input_image = image_norm
  process_median.kernel_mode = imagedev.MedianFilter2d.KernelMode.DISK
  process_median.kernel_radius = 1
  process_median.execute()
  im_median = process_median.output_image

  # Display and save the resulting image as a png file
  #imagedev.imshow(im_median)
  ioformat.write_view(im_median, "T01_01_output.png")

  # ImageDev library finalization
  imagedev.finish()
except Exception as error:
  # Print potential exception in the standard output
  print("HelloImageDev exception: " + str(error))

See also