extrafiltersplugin.cpp Example File

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  #include <QtWidgets>

  #include <math.h>
  #include <stdlib.h>

  #include "extrafiltersplugin.h"

  QStringList ExtraFiltersPlugin::filters() const
  {
      return QStringList() << tr("Flip Horizontally") << tr("Flip Vertically")
                           << tr("Smudge...") << tr("Threshold...");
  }

  QImage ExtraFiltersPlugin::filterImage(const QString &filter,
                                         const QImage &image, QWidget *parent)
  {
      QImage original = image.convertToFormat(QImage::Format_RGB32);
      QImage result = original;

      if (filter == tr("Flip Horizontally")) {
          for (int y = 0; y < original.height(); ++y) {
              for (int x = 0; x < original.width(); ++x) {
                  int pixel = original.pixel(original.width() - x - 1, y);
                  result.setPixel(x, y, pixel);
              }
          }
      } else if (filter == tr("Flip Vertically")) {
          for (int y = 0; y < original.height(); ++y) {
              for (int x = 0; x < original.width(); ++x) {
                  int pixel = original.pixel(x, original.height() - y - 1);
                  result.setPixel(x, y, pixel);
              }
          }
      } else if (filter == tr("Smudge...")) {
          bool ok;
          int numIters = QInputDialog::getInt(parent, tr("Smudge Filter"),
                                      tr("Enter number of iterations:"),
                                      5, 1, 20, 1, &ok);
          if (ok) {
              for (int i = 0; i < numIters; ++i) {
                  for (int y = 1; y < original.height() - 1; ++y) {
                      for (int x = 1; x < original.width() - 1; ++x) {
                          int p1 = original.pixel(x, y);
                          int p2 = original.pixel(x, y + 1);
                          int p3 = original.pixel(x, y - 1);
                          int p4 = original.pixel(x + 1, y);
                          int p5 = original.pixel(x - 1, y);

                          int red = (qRed(p1) + qRed(p2) + qRed(p3) + qRed(p4)
                                     + qRed(p5)) / 5;
                          int green = (qGreen(p1) + qGreen(p2) + qGreen(p3)
                                       + qGreen(p4) + qGreen(p5)) / 5;
                          int blue = (qBlue(p1) + qBlue(p2) + qBlue(p3)
                                      + qBlue(p4) + qBlue(p5)) / 5;
                          int alpha = (qAlpha(p1) + qAlpha(p2) + qAlpha(p3)
                                       + qAlpha(p4) + qAlpha(p5)) / 5;

                          result.setPixel(x, y, qRgba(red, green, blue, alpha));
                      }
                  }
              }
          }
      } else if (filter == tr("Threshold...")) {
          bool ok;
          int threshold = QInputDialog::getInt(parent, tr("Threshold Filter"),
                                                   tr("Enter threshold:"),
                                                   10, 1, 256, 1, &ok);
          if (ok) {
              int factor = 256 / threshold;
              for (int y = 0; y < original.height(); ++y) {
                  for (int x = 0; x < original.width(); ++x) {
                      int pixel = original.pixel(x, y);
                      result.setPixel(x, y, qRgba(qRed(pixel) / factor * factor,
                                                  qGreen(pixel) / factor * factor,
                                                  qBlue(pixel) / factor * factor,
                                                  qAlpha(pixel)));
                  }
              }
          }
      }
      return result;
  }