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

        /****************************************************************************
        **
        ** Copyright (C) 2005-2005 Trolltech AS. All rights reserved.
        **
        ** This file is part of the documentation of the Qt Toolkit.
        **
        ** This file may be used under the terms of the GNU General Public
    ** License version 2.0 as published by the Free Software Foundation
    ** and appearing in the file LICENSE.GPL included in the packaging of
    ** this file.  Please review the following information to ensure GNU
    ** General Public Licensing requirements will be met:
    ** http://www.trolltech.com/products/qt/opensource.html
    **
    ** If you are unsure which license is appropriate for your use, please
    ** review the following information:
    ** http://www.trolltech.com/products/qt/licensing.html or contact the
    ** sales department at sales@trolltech.com.
        **
        ** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        **
        ****************************************************************************/

        #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_PLUGIN(ExtraFiltersPlugin)