- Qt 5.5
- Qt Widgets
- Plug & Paint Basic Tools Example
- basictoolsplugin.cpp Example File
- Qt 5.5.1 Reference Documentation

# basictoolsplugin.cpp Example File

tools/plugandpaintplugins/basictools/basictoolsplugin.cpp

    /****************************************************************************
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    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
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    #include <QtWidgets>

    #include <cmath>
    #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 * std::cos(0.8 * i * Pi),
                            50 + 40 * std::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;
    }