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# extrafiltersplugin.cpp Example File
tools/plugandpaintplugins/extrafilters/extrafiltersplugin.cpp

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     #include <QtGui>

     #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::getInteger(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::getInteger(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;
     }

     Q_EXPORT_PLUGIN2(pnp_extrafilters, ExtraFiltersPlugin)