- Qt 5.5
- Qt Widgets
- Scribble Example
- scribblearea.cpp Example File
- Qt 5.5.1 Reference Documentation

# scribblearea.cpp Example File

widgets/scribble/scribblearea.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** 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.
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    **
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    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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    #include <QtWidgets>
    #ifndef QT_NO_PRINTER
    #include <QPrinter>
    #include <QPrintDialog>
    #endif

    #include "scribblearea.h"

    ScribbleArea::ScribbleArea(QWidget *parent)
        : QWidget(parent)
    {
        setAttribute(Qt::WA_StaticContents);
        modified = false;
        scribbling = false;
        myPenWidth = 1;
        myPenColor = Qt::blue;
    }

    bool ScribbleArea::openImage(const QString &fileName)
    {
        QImage loadedImage;
        if (!loadedImage.load(fileName))
            return false;

        QSize newSize = loadedImage.size().expandedTo(size());
        resizeImage(&loadedImage, newSize);
        image = loadedImage;
        modified = false;
        update();
        return true;
    }

    bool ScribbleArea::saveImage(const QString &fileName, const char *fileFormat)
    {
        QImage visibleImage = image;
        resizeImage(&visibleImage, size());

        if (visibleImage.save(fileName, fileFormat)) {
            modified = false;
            return true;
        } else {
            return false;
        }
    }

    void ScribbleArea::setPenColor(const QColor &newColor)
    {
        myPenColor = newColor;
    }

    void ScribbleArea::setPenWidth(int newWidth)
    {
        myPenWidth = newWidth;
    }

    void ScribbleArea::clearImage()
    {
        image.fill(qRgb(255, 255, 255));
        modified = true;
        update();
    }

    void ScribbleArea::mousePressEvent(QMouseEvent *event)
    {
        if (event->button() == Qt::LeftButton) {
            lastPoint = event->pos();
            scribbling = true;
        }
    }

    void ScribbleArea::mouseMoveEvent(QMouseEvent *event)
    {
        if ((event->buttons() & Qt::LeftButton) && scribbling)
            drawLineTo(event->pos());
    }

    void ScribbleArea::mouseReleaseEvent(QMouseEvent *event)
    {
        if (event->button() == Qt::LeftButton && scribbling) {
            drawLineTo(event->pos());
            scribbling = false;
        }
    }

    void ScribbleArea::paintEvent(QPaintEvent *event)
    {
        QPainter painter(this);
        QRect dirtyRect = event->rect();
        painter.drawImage(dirtyRect, image, dirtyRect);
    }

    void ScribbleArea::resizeEvent(QResizeEvent *event)
    {
        if (width() > image.width() || height() > image.height()) {
            int newWidth = qMax(width() + 128, image.width());
            int newHeight = qMax(height() + 128, image.height());
            resizeImage(&image, QSize(newWidth, newHeight));
            update();
        }
        QWidget::resizeEvent(event);
    }

    void ScribbleArea::drawLineTo(const QPoint &endPoint)
    {
        QPainter painter(&image);
        painter.setPen(QPen(myPenColor, myPenWidth, Qt::SolidLine, Qt::RoundCap,
                            Qt::RoundJoin));
        painter.drawLine(lastPoint, endPoint);
        modified = true;

        int rad = (myPenWidth / 2) + 2;
        update(QRect(lastPoint, endPoint).normalized()
                                         .adjusted(-rad, -rad, +rad, +rad));
        lastPoint = endPoint;
    }

    void ScribbleArea::resizeImage(QImage *image, const QSize &newSize)
    {
        if (image->size() == newSize)
            return;

        QImage newImage(newSize, QImage::Format_RGB32);
        newImage.fill(qRgb(255, 255, 255));
        QPainter painter(&newImage);
        painter.drawImage(QPoint(0, 0), *image);
        *image = newImage;
    }

    void ScribbleArea::print()
    {
    #if !defined(QT_NO_PRINTER) && !defined(QT_NO_PRINTDIALOG)
        QPrinter printer(QPrinter::HighResolution);

        QPrintDialog printDialog(&printer, this);
        if (printDialog.exec() == QDialog::Accepted) {
            QPainter painter(&printer);
            QRect rect = painter.viewport();
            QSize size = image.size();
            size.scale(rect.size(), Qt::KeepAspectRatio);
            painter.setViewport(rect.x(), rect.y(), size.width(), size.height());
            painter.setWindow(image.rect());
            painter.drawImage(0, 0, image);
        }
    #endif // QT_NO_PRINTER
    }