Qt 5.11 | Qt Widgets | Plug & Paint Extra Filters Example | extrafiltersplugin.cpp Example File

Qt 5.11.3 Reference Documentation

# extrafiltersplugin.cpp Example File

tools/plugandpaint/plugins/extrafilters/extrafiltersplugin.cpp

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      #include "extrafiltersplugin.h"

      #include <QtWidgets>

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

      QStringList ExtraFiltersPlugin::filters() const
      {
          return {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) {
                      QRgb 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) {
                      QRgb 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) {
                              QRgb p1 = original.pixel(x, y);
                              QRgb p2 = original.pixel(x, y + 1);
                              QRgb p3 = original.pixel(x, y - 1);
                              QRgb p4 = original.pixel(x + 1, y);
                              QRgb 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) {
                          QRgb 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;
      }