The contrast operation is used to enhance the visual quality of the image represented by a raster file. The available methods in TerraAmazon are:
Histogram Equalization: Using this method, the histogram of the image will be equalized automatically.
Linear: The user defines a new minimum and maximum value for the pixels in the image. The algorithm then applies a linear function over the pixels using those 2 values.
Log: The contrasted image will be created by using a log function.
Square: The contrasted image will be created by using a square function.
Square Root: The contrasted image will be created by using a square root function.
Mean and Standard Deviation: The contrasted image will have a predefined mean and standard deviation, defined by the user.
Decorrelation Enhancement: Uses the principal components to contrast the raster.
Click on the layer in the layer explorer and select PROCESSING → RASTER PROCESSING → CONTRAST in the main menu.
Select the type of contrast to be used, for instance: Linear.
In Raster Bands check the desired bands and set the specific parameters which will varies depending on the contrast type chosen. Double click over the cell of each parameter to make the cell editable and then change the value and press enter:
If Linear, Square, Square Root or Log: set the new value for Minimum and/or Maximum,
If Histogram Equalization: set the new value for Maximum.
If Mean and Standard Deviation: set the new value for Mean and/or Std Dev.
If Decorrelation Enhancement: none extra parameters will be necessary.
Check the Preview box to have a preview of the contrast with the parameters informed in the visualization area.
The Histogram tab presents the histogram to help in the contrast operation.
The Input histogram represents the histogram of the selected band.
The Output is as the histogram would be if the contrast was applied.
Using the mouse buttons (right button for maximum and left button for minimum) you can purchase the pixel value from the histogram, helping to define the parameters of each type of contrast.
Histogram Area: select which area will be used as reference to do the contrast: Use all image, use visible area showed in the visualization area or a new region of interest created by the user (click on the New ROI button to mark the region on the visualization area).
Repository -
Select one type of repository by
clicking on the
button to save the output layer as a file or on the
button to save it in the database.
Layer Name - inform the raster name.
Press the OK button to save the resulting contrasted raster.