子类化QWidget

源码：

iconeditor.h

#ifndef ICONEDITOR_H

#define ICONEDITOR_H



#include <QColor>

#include <QImage>

#include <QWidget>



class IconEditor : public QWidget

{

    Q_OBJECT


　　//Q_PROPERTY()宏来设置属性
    Q_PROPERTY(QColor penColor READ penColor WRITE setPenColor)

    Q_PROPERTY(QImage iconImage READ iconImage WRITE setIconImage)

    Q_PROPERTY(int zoomFactor READ zoomFactor WRITE setZoomFactor)



public:

    IconEditor(QWidget *parent = 0);



    void setPenColor(const QColor &newColor);

    QColor penColor() const { return curColor; }

    void setZoomFactor(int newZoom);

    int zoomFactor() const { return zoom; }

    void setIconImage(const QImage &newImage);

    QImage iconImage() const { return image; }

    QSize sizeHint() const;



protected:

    void mousePressEvent(QMouseEvent *event);

    void mouseMoveEvent(QMouseEvent *event);

    void paintEvent(QPaintEvent *event);



private:

    void setImagePixel(const QPoint &pos, bool opaque);

    QRect pixelRect(int i, int j) const;



    QColor curColor;

    QImage image;

    int zoom;

};



#endif

 iconeditor.cpp

#include <QtGui>



#include "iconeditor.h"



IconEditor::IconEditor(QWidget *parent)

    : QWidget(parent)

{

    setAttribute(Qt::WA_StaticContents);

    setSizePolicy(QSizePolicy::Minimum, QSizePolicy::Minimum);



    curColor = Qt::black;

    zoom = 8;  //缩放因子

    image = QImage(16, 16, QImage::Format_ARGB32);   //16*16的像素大小和32位的ARGB
    image.fill(qRgba(0, 0, 0, 0));

}



void IconEditor::setPenColor(const QColor &newColor)

{

    curColor = newColor;

}



void IconEditor::setZoomFactor(int newZoom)

{

    if (newZoom < 1)

        newZoom = 1;



    if (newZoom != zoom) {

        zoom = newZoom;

        update();

        updateGeometry();

    }

}



void IconEditor::setIconImage(const QImage &newImage)

{

    if (newImage != image) {

        image = newImage.convertToFormat(QImage::Format_ARGB32);

        update();

        updateGeometry();

    }

}



QSize IconEditor::sizeHint() const

{

    QSize size = zoom * image.size();

    if (zoom >= 3)

        size += QSize(1, 1);

    return size;

}



void IconEditor::mousePressEvent(QMouseEvent *event)

{

    if (event->button() == Qt::LeftButton) {

        setImagePixel(event->pos(), true);

    } else if (event->button() == Qt::RightButton) {

        setImagePixel(event->pos(), false);

    }

}



void IconEditor::mouseMoveEvent(QMouseEvent *event)

{

    if (event->buttons() & Qt::LeftButton) {

        setImagePixel(event->pos(), true);

    } else if (event->buttons() & Qt::RightButton) {

        setImagePixel(event->pos(), false);

    }

}



void IconEditor::paintEvent(QPaintEvent *event)

{

    QPainter painter(this);



    if (zoom >= 3) {

        painter.setPen(palette().foreground().color());

        for (int i = 0; i <= image.width(); ++i)

            painter.drawLine(zoom * i, 0,

                             zoom * i, zoom * image.height());

        for (int j = 0; j <= image.height(); ++j)

            painter.drawLine(0, zoom * j,

                             zoom * image.width(), zoom * j);

    }



    for (int i = 0; i < image.width(); ++i) {

        for (int j = 0; j < image.height(); ++j) {

            QRect rect = pixelRect(i, j);

            if (!event->region().intersect(rect).isEmpty()) {

                QColor color = QColor::fromRgba(image.pixel(i, j));

                if (color.alpha() < 255)

                    painter.fillRect(rect, Qt::white);

                painter.fillRect(rect, color);

            }

        }

    }

}



void IconEditor::setImagePixel(const QPoint &pos, bool opaque)

{

    int i = pos.x() / zoom;

    int j = pos.y() / zoom;



    if (image.rect().contains(i, j)) {

        if (opaque) {

            image.setPixel(i, j, penColor().rgba());

        } else {

            image.setPixel(i, j, qRgba(0, 0, 0, 0));

        }



        update(pixelRect(i, j));

    }

}



QRect IconEditor::pixelRect(int i, int j) const

{

    if (zoom >= 3) {

        return QRect(zoom * i + 1, zoom * j + 1, zoom - 1, zoom - 1);

    } else {

        return QRect(zoom * i, zoom * j, zoom, zoom);

    }

}

main.c

#include <QApplication>



#include "iconeditor.h"



int main(int argc, char *argv[])

{

    QApplication app(argc, argv);

    IconEditor iconEditor;

    iconEditor.setWindowTitle(QObject::tr("Icon Editor"));

    iconEditor.setIconImage(QImage(":/images/mouse.png"));

    iconEditor.show();

    return app.exec();

}

 

附加小知识：

1：一个具有32位色深的图像分别对每一个像素各使用8位来存储它的红绿蓝分量，剩余的8位存储这个像素的alpha分量(即不透明度)

  如： QRgb red = qRgba(255, 0,0,255);  或 QRgb red = 0xFFFF0000;

2：Qt提供来俩种存储颜色的类型：QRgb和QColor

3：QPainter::drawLine() 例：painter.drawLine(x1,y1,x2,y2);

4：每一个窗口部件都会配备一个调色板，由它来确定做什么事应该使用什么颜色

5：QWidget::palette()函数可用返回窗口部件的调色板，它是一个QPalette型对象

6：QRect(x ,y , width, height);