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## Lab: Exponential Contrast Enhancement

[Exercises] [Workspace]

Purpose: The purpose of this lab is to experiment with a technique of image contrast enhancement achieved by applying exponential colormaps to images. This technique is useful for increasing contrast in bright images.

Activities:

1. Visualize the original over-bright image.

   1. Read and display the $DIP/data/cells-tissue-saturate.kdf image using the operators User defined and Display Image.

      1. Glyphs:Input/Output:Data Files:User defined
      2. Glyphs:Visualization:Non-Interactive Display:Display Image

   2. Calculate the histogram and plot it using the Histogram and Display 2D Plot operators.

      1. Glyphs:Data Manip:Histogram Operators:Histogram
      2. Glyphs:Visualization:Plot Display:Display 2D Plot

2. Visualize the exponential color table.

   1. Print the contents of the $DIP/data/exp-256-lut.kdf color table using the operator Print Data and File Viewer. Set the Print Data parameters so that "Map Indexing" and "Map Data" are selected.

      1. Glyphs:Input/Output:Data Files:User defined
      2. Glyphs:Input/Output:Information:Print Data
      3. Glyphs:Input/Output:Information:File Viewer

   2. Visualize the color table by plotting its values. Transfer the data from the map segment to the value segment using the Copy to Value operator, and plot it using the Display 2D Plot operator.

      1. Glyphs:Data Manip:Segment Operators:Copy to Value
      2. Glyphs:Visualization:Plot Display:Display 2D Plot

3. This experiment shows three ways of enhancing the image using the exponential colormap.

   1. Use the operator Display Image to display the $DIP/data/cells-tissue-saturate.kdf image. Connect the colormap file to the last entry of the Display Image operator ("Colormap Image").

      1. Glyphs:Visualization:Non-Interactive Display:Display Image

   2. Insert the color table in the image file using the operator Insert Segments. Insert the value segment of the $DIP/data/cells-tissue-saturate.kdf file with the color table file. Display it with Display Image.

      1. Glyphs:Data Manip:Segment Operators:Insert Segments
      2. Glyphs:Visualization:Non-Interactive Display:Display Image

   3. Use the image generated in the Part 3-B, and explicitly map the data through the colormap using the operator Map Data. Calculate and plot the histogram of this image and compare it with the original image histogram.

      1. Glyphs:Data Manip:Map Operators:Map Data
      2. Glyphs:Visualization:Non-Interactive Display:Display Image
      3. Glyphs:Data Manip:Histogram Operators:Histogram
      4. Glyphs:Visualization:Plot Display:Display 2D Plot

Exercises

1. Use the operator Data Object Info to see the differences in the file contents of methods 2 and 3 above.

   Glyphs:Input/Output:Information:Data Object Info

   Glyphs:Input/Output:Information:File Viewer

Khoros Workspace
Execute the visual program c4s8contrast-exp.wk