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# basictoolsplugin.cpp Example File
tools/plugandpaintplugins/basictools/basictoolsplugin.cpp

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     #include <QtGui>

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

     #include "basictoolsplugin.h"

     const float Pi = 3.14159f;

     QStringList BasicToolsPlugin::brushes() const
     {
         return QStringList() << tr("Pencil") << tr("Air Brush")
                              << tr("Random Letters");
     }

     QRect BasicToolsPlugin::mousePress(const QString &brush, QPainter &painter,
                                        const QPoint &pos)
     {
         return mouseMove(brush, painter, pos, pos);
     }

     QRect BasicToolsPlugin::mouseMove(const QString &brush, QPainter &painter,
                                       const QPoint &oldPos, const QPoint &newPos)
     {
         painter.save();

         int rad = painter.pen().width() / 2;
         QRect boundingRect = QRect(oldPos, newPos).normalized()
                                                   .adjusted(-rad, -rad, +rad, +rad);
         QColor color = painter.pen().color();
         int thickness = painter.pen().width();
         QColor transparentColor(color.red(), color.green(), color.blue(), 0);

         if (brush == tr("Pencil")) {
             painter.drawLine(oldPos, newPos);
         } else if (brush == tr("Air Brush")) {
             int numSteps = 2 + (newPos - oldPos).manhattanLength() / 2;

             painter.setBrush(QBrush(color, Qt::Dense6Pattern));
             painter.setPen(Qt::NoPen);

             for (int i = 0; i < numSteps; ++i) {
                 int x = oldPos.x() + i * (newPos.x() - oldPos.x()) / (numSteps - 1);
                 int y = oldPos.y() + i * (newPos.y() - oldPos.y()) / (numSteps - 1);

                 painter.drawEllipse(x - (thickness / 2), y - (thickness / 2),
                                     thickness, thickness);
             }
         } else if (brush == tr("Random Letters")) {
             QChar ch('A' + (qrand() % 26));

             QFont biggerFont = painter.font();
             biggerFont.setBold(true);
             biggerFont.setPointSize(biggerFont.pointSize() + thickness);
             painter.setFont(biggerFont);

             painter.drawText(newPos, QString(ch));

             QFontMetrics metrics(painter.font());
             boundingRect = metrics.boundingRect(ch);
             boundingRect.translate(newPos);
             boundingRect.adjust(-10, -10, +10, +10);
         }
         painter.restore();
         return boundingRect;
     }

     QRect BasicToolsPlugin::mouseRelease(const QString & /* brush */,
                                          QPainter & /* painter */,
                                          const QPoint & /* pos */)
     {
         return QRect(0, 0, 0, 0);
     }

     QStringList BasicToolsPlugin::shapes() const
     {
         return QStringList() << tr("Circle") << tr("Star") << tr("Text...");
     }

     QPainterPath BasicToolsPlugin::generateShape(const QString &shape,
                                                  QWidget *parent)
     {
         QPainterPath path;

         if (shape == tr("Circle")) {
             path.addEllipse(0, 0, 50, 50);
         } else if (shape == tr("Star")) {
             path.moveTo(90, 50);
             for (int i = 1; i < 5; ++i) {
                 path.lineTo(50 + 40 * cos(0.8 * i * Pi),
                             50 + 40 * sin(0.8 * i * Pi));
             }
             path.closeSubpath();
         } else if (shape == tr("Text...")) {
             QString text = QInputDialog::getText(parent, tr("Text Shape"),
                                                  tr("Enter text:"),
                                                  QLineEdit::Normal, tr("Qt"));
             if (!text.isEmpty()) {
                 QFont timesFont("Times", 50);
                 timesFont.setStyleStrategy(QFont::ForceOutline);
                 path.addText(0, 0, timesFont, text);
             }
         }

         return path;
     }

     QStringList BasicToolsPlugin::filters() const
     {
         return QStringList() << tr("Invert Pixels") << tr("Swap RGB")
                              << tr("Grayscale");
     }

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

         if (filter == tr("Invert Pixels")) {
             result.invertPixels();
         } else if (filter == tr("Swap RGB")) {
             result = result.rgbSwapped();
         } else if (filter == tr("Grayscale")) {
             for (int y = 0; y < result.height(); ++y) {
                 for (int x = 0; x < result.width(); ++x) {
                     int pixel = result.pixel(x, y);
                     int gray = qGray(pixel);
                     int alpha = qAlpha(pixel);
                     result.setPixel(x, y, qRgba(gray, gray, gray, alpha));
                 }
             }
         }
         return result;
     }

     Q_EXPORT_PLUGIN2(pnp_basictools, BasicToolsPlugin)