ColorFilterHistogram.cpp

/******************************************************************************************************
 * (C) 2014 markummitchell@github.com. This file is part of Engauge Digitizer, which is released      *
 * under GNU General Public License version 2 (GPLv2) or (at your option) any later version. See file *
 * LICENSE or go to gnu.org/licenses for details. Distribution requires prior written permission.     *
 ******************************************************************************************************/
 
#include "ColorFilter.h"
#include "ColorFilterHistogram.h"
#include "EngaugeAssert.h"
#include <QImage>
 
ColorFilterHistogram::ColorFilterHistogram()
{
}
 
int ColorFilterHistogram::binFromPixel (const ColorFilter &filter,
                                        ColorFilterMode colorFilterMode,
                                        const QColor &pixel,
                                        const QRgb &rgbBackground) const
{
  // Instead of mapping from s=0 through 1 to bin=0 through HISTOGRAM_BINS-1, we
  // map it to bin=1 through HISTOGRAM_BINS-2 so first and last bin are zero. The
  // result is a peak at the start or end is complete and easier to read
  double s = filter.pixelToZeroToOneOrMinusOne (colorFilterMode,
                                                pixel,
                                                rgbBackground);
  ENGAUGE_ASSERT (s <= 1.0);
 
  int bin = -1;
 
  if (s >= 0) {
 
    bin = FIRST_NON_EMPTY_BIN_AT_START () + s * (LAST_NON_EMPTY_BIN_AT_END () - FIRST_NON_EMPTY_BIN_AT_START ());
 
  }
 
  return bin;
}
 
void ColorFilterHistogram::generate (const ColorFilter &filter,
                                     double histogramBins [],
                                     ColorFilterMode colorFilterMode,
                                     const QImage &image,
                                     int &maxBinCount) const
{
  // Initialize histogram bins
  int bin;
  for (bin = 0; bin < HISTOGRAM_BINS (); bin++) {
    histogramBins [bin] = 0;
  }
 
  QRgb rgbBackground = filter.marginColor(&image);
 
  // Populate histogram bins
  maxBinCount = 0;
  for (int x = 0; x < image.width(); x++) {
    for (int y = 0; y < image.height(); y++) {
 
      QColor pixel (image.pixel (x, y));
      int bin = binFromPixel (filter,
                              colorFilterMode,
                              pixel,
                              rgbBackground);
      if (bin >= 0) {
 
        ENGAUGE_ASSERT ((FIRST_NON_EMPTY_BIN_AT_START () <= bin) &&
                        (LAST_NON_EMPTY_BIN_AT_END () >= bin));
        ++(histogramBins [bin]);
 
        if (histogramBins [bin] > maxBinCount) {
          maxBinCount = histogramBins [bin];
        }
      }
    }
  }
}
 
int ColorFilterHistogram::valueFromBin (const ColorFilter &filter,
                                        ColorFilterMode colorFilterMode,
                                        int bin)
{
  // Just do everything in binFromPixel backwards
  double s = (double) (bin - FIRST_NON_EMPTY_BIN_AT_START ()) / (double) (LAST_NON_EMPTY_BIN_AT_END () - FIRST_NON_EMPTY_BIN_AT_START ());
  s = qMin (qMax (s, 0.0), 1.0);
 
  return filter.zeroToOneToValue (colorFilterMode,
                                  s);
}