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;
 }