Plugins: 04 Process Input Data

processInputData() is called when either the process properties or the input data for your algorithm have changed by user interaction or any preceding process items. This is the place where you do the heavy lifting.

Basic concept for image processing algorithms

Delete the previous result data in order to prevent memory leaks and create a new instance for saving your algorithm's result.

// delete previous result
delete _result;
_result = new IPLImage( image->type(), width, height );

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Get the process properties which you have defined before in init()

// get properties
float threshold = getProcessPropertyDouble("threshold");

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Iterate over image planes (input channels). OpenMP can be used to distribute the processing of each plane to a different thread, which results in much faster processing on muticore CPUs.

#pragma omp parallel for
for(int planeNr=0; planeNr < nrOfPlanes; planeNr++)

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Iterate over pixel rows and columns

for(int y=0; y<height; y++)
    for(int x=0; x<width; x++)

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Access input pixels

input->plane(planeNr)->p(x, y);  // fast, unchecked
input->plane(planeNr)->cp(x, y); // zero for invalid coordinates
input->plane(planeNr)->bp(x, y); // extend border mode
input->plane(planeNr)->wp(x, y); // wrap border mode

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Write to output pixels

_result->plane(planeNr)->p(x, y) = value;

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Notify the GUI about your progress between 0 and 100%

// progress
notifyProgressEventHandler(100*progress++/maxProgress);

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