basictoolsplugin.cpp Example File

  /****************************************************************************
  **
  ** Copyright (C) 2016 The Qt Company Ltd.
  ** Contact: https://www.qt.io/licensing/
  **
  ** This file is part of the examples of the Qt Toolkit.
  **
  ** $QT_BEGIN_LICENSE:BSD$
  ** Commercial License Usage
  ** Licensees holding valid commercial Qt licenses may use this file in
  ** accordance with the commercial license agreement provided with the
  ** Software or, alternatively, in accordance with the terms contained in
  ** a written agreement between you and The Qt Company. For licensing terms
  ** and conditions see https://www.qt.io/terms-conditions. For further
  ** information use the contact form at https://www.qt.io/contact-us.
  **
  ** BSD License Usage
  ** Alternatively, you may use this file under the terms of the BSD license
  ** as follows:
  **
  ** "Redistribution and use in source and binary forms, with or without
  ** modification, are permitted provided that the following conditions are
  ** met:
  **   * Redistributions of source code must retain the above copyright
  **     notice, this list of conditions and the following disclaimer.
  **   * Redistributions in binary form must reproduce the above copyright
  **     notice, this list of conditions and the following disclaimer in
  **     the documentation and/or other materials provided with the
  **     distribution.
  **   * Neither the name of The Qt Company Ltd nor the names of its
  **     contributors may be used to endorse or promote products derived
  **     from this software without specific prior written permission.
  **
  **
  ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
  **
  ** $QT_END_LICENSE$
  **
  ****************************************************************************/

  #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;
  }