basictoolsplugin.cpp Example File

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 #include <QtWidgets>

 #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;
 }