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

Input:

• One 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: Raster

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.

To create an image with a linear contrast, the following parameters are necessary:

// ... (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)

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

To create an image with an equalization of histogram contrast, the following parameters are necessary:

// ... (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)

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

To create an image with a predefined mean and standard deviation, the following parameters are necessary:

// ... (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)

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

// 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;