====== RP → Contrast ======

This module implements methods to apply contrast enhancement on the selected bands of a raster.

Input:
  * One [[wiki:designimplementation:raster|Raster]]
  * A vector of band indices where the contrast will be applied.

The available methods in TerraLib are:
  * [[#Linear]]
  * [[#Histogram Equalization]]
  * [[#Set Mean and Std]]

Dependencies: [[wiki:designimplementation:raster|Raster]]

===== Linear =====

The user defines a new minimum and maximum values for the pixels in the image. The algorithm then applies a linear function over the pixels using this 2 values.

{{:wiki:designimplementation:rp:linear-contrast.png?600|}}

==== Example of use ====

To create an image with a linear contrast, the following parameters are necessary:
<code c++>
// ... (set input data)

// link specific parameters with chosen implementation
te::rp::Contrast::InputParameters contInputParameters;
contInputParameters.m_type = te::rp::Contrast::InputParameters::LinearContrastT;
contInputParameters.m_lCMinInput.push_back(100);
contInputParameters.m_lCMaxInput.push_back(200);
contInputParameters.m_inRasterPtr = rin;
for (unsigned b = 0; b < rin->getNumberOfBands(); b++)
  contInputParameters.m_inRasterBands.push_back(b);

// ... (set output data and start algorithm)
</code>

===== Histogram Equalization =====

Using this method, the histogram of the image will be equalized automatically.

==== Example of use ====

To create an image with an equalization of histogram contrast, the following parameters are necessary:
<code c++>
// ... (set input data)

// link specific parameters with chosen implementation
te::rp::Contrast::InputParameters contInputParameters;
contInputParameters.m_type = te::rp::Contrast::InputParameters::HistogramEqualizationContrastT;
contInputParameters.m_hECMaxInput.push_back(255); // set this parameter to normalize raster [0, 255]
contInputParameters.m_inRasterPtr = rin;
for (unsigned b = 0; b < rin->getNumberOfBands(); b++)
  contInputParameters.m_inRasterBands.push_back(b);

// ... (set output data and start algorithm)
</code>

===== Set Mean and Std =====

The contrasted image will have a predefined mean and standard deviation, defined by the user.

==== Example of use ====

To create an image with a predefined mean and standard deviation, the following parameters are necessary:
<code c++>
// ... (set input data)

// link specific parameters with chosen implementation
te::rp::Contrast::InputParameters contInputParameters;
contInputParameters.m_type = te::rp::Contrast::InputParameters::SetMeanAndStdContrastT;
contInputParameters.m_inRasterPtr = rin;
for (unsigned b = 0; b < rin->getNumberOfBands(); b++)
{
  contInputParameters.m_inRasterBands.push_back(b);
  contInputParameters.m_sMASCMeanInput.push_back(127);
  contInputParameters.m_sMASCStdInput.push_back(100);
}

// ... (set output data and start algorithm)
</code>

====== From theory to practice ======

The following code shows how to create an image with linear contrast:

<code c++>
// open input raster
std::map<std::string, std::string> rinfo;
rinfo["URI"] = "input.tif";
te::rst::Raster* rin = te::rst::RasterFactory::open(rinfo);

// link specific parameters with chosen implementation
te::rp::Contrast::InputParameters contInputParameters;
contInputParameters.m_type = te::rp::Contrast::InputParameters::LinearContrastT;
contInputParameters.m_inRasterPtr = rin;
for (unsigned b = 0; b < rin->getNumberOfBands(); b++)
{
  contInputParameters.m_inRasterBands.push_back(b);
  contInputParameters.m_lCMinInput.push_back(100);
  contInputParameters.m_lCMaxInput.push_back(200);
}

// set output raster for linear contrast
std::map<std::string, std::string> orinfo;
orinfo["URI"] = "output-linear-contrast.tif";

te::rp::Contrast::OutputParameters contOutputParameters;
contOutputParameters.m_createdOutRasterInfo = orinfo;
contOutputParameters.m_createdOutRasterDSType = "GDAL";

// execute the algorithm
te::rp::Contrast continstance;
bool initok = continstance.initialize(contInputParameters);
if (initok)
  continstance.execute(contOutputParameters);

// clean up
delete rin;
</code>