Logarithm Contrast Enhancement
Building the Cantata Workspace
1. Contrast Enhancement using explicitly the log function
- Read and display the $DIP/data/myelin.viff image using the
operators
User defined and
Display Image.
- Apply the
Logarithm operator the the image and display the result using the
Display Image operator. The resultant image has a much better contrast
in the dark areas.
- You can notice that the pixels values of the previous image
are of type float varying from 0 to log(1+255) which is approximately
2.4. Use the operator
Normalize to convert the image to pixels of type unsigned byte varying
from 0 to 255.
2. Contrast Enhancement using a logarithmic color table
User the colormap file $DIP/data/log-256-lut.viff.
Print its data using the operator
Print Data with the
parameters Map Indexing and Map Data selected.
This experiment shows three ways of enhancing the image using the logarithm
colormap.
- Use the operator
Display Image to display the myelin.viff image. Connect the
colormap file to the last entry of the
Display Image operator (Colormap Image).
- Insert the colortable in the image file using the operator
Insert Segments.
Insert the Value segment of myelin.viff file with the
colortable file. Display it with
Display Image.
- Use the image generated in the previous method and explicitly
map the data through the colormap using the operator
Map Data.
Exercises
- Explain the differences using the three methods of using the
colortable. Use the operator
Data Object Info
to see the differences in the file contents of methods 2 and 3.
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