qt实现头像上传功能

想必大家都使用过qt的自定义头像功能吧，那么图1应该不会陌生，本片文章我就是要模拟一个这样的功能，虽然没有这么强大的效果，但是能够满足一定的需求。

图1 qq上传图片

首先在讲解功能之前，我先给出一片文章，QT实现的类似QQ的头像选择框，这篇文章也是讲解头像上传功能的，而我自己的代码是从这个demo中优化而来，不仅对代码进行了重构，而且处理了快速拖动时，边框消失的问题。使用事件和双缓冲来尽量减少重新绘制的几率。接下里我会一步一步进行讲解，怎么实现图片自定义截取功能。
一、概要
首选，我给出4个类，并给出他们的解释
1、PicturePreviewPanel：图标展示框，控件基类
2、BackgroundWidget：阴影窗口，是PicturePreviewPanel子类
3、CutShape：交互图形基类，实现了拖拽和放大缩小功能
4、CutRound：圆形剪贴，父类为CutShape，实现父类的paintInit接口重绘
5、CutRectangle：矩形剪贴，父类为CutShape，实现父类的paintInit接口重绘
二、详情
理解了上述5个类之后，接下来我分别讲解下类的头文件和重要的实现接口，其中自定义图形类也可以自己在扩充
头文件代码如下，有部分注释，代码应该不难理解，开发过程中只需要声明PicturePreviewPanel类，并调用期LoadPicture接口就可以加载图片，并进行图片剪切

 #include <QWidget>

 class QLabel;

 enum ShapeType
 {
     Rect,//矩形
     Round,//圆形
 };

 //剪贴图基类 实现了基本的交互功能，并绘制了部分图案，主要的团绘制在子类实现，通过实现paintInit接口
 class CutShape : public QWidget
 {
 public:
     CutShape(QWidget * parent = nullptr);
     ~CutShape();

 public:
     QPainterPath CutRegion();

 protected:
     //QWidget
     virtual void mousePressEvent(QMouseEvent *) Q_DECL_OVERRIDE;
     virtual void mouseMoveEvent(QMouseEvent *) Q_DECL_OVERRIDE;
     virtual void mouseReleaseEvent(QMouseEvent *) Q_DECL_OVERRIDE;
     virtual void resizeEvent(QResizeEvent *) Q_DECL_OVERRIDE;
     virtual void paintEvent(QPaintEvent *) Q_DECL_OVERRIDE;

     virtual bool paintInit(QPaintEvent *, QPaintDevice *) = ;
     virtual QPainterPath Region(){ return QPainterPath(); };

 protected:
     ShapeType m_Type;
     bool m_MouseDown = false;
     bool m_IsMoving = false;
     bool m_IsFirst = true;
     int border = ;

 private:
     QRect getResizeGem(QRect oldgeo, QPoint mousePoint, bool & ignore);

 private:
     bool m_EnableRepaint = true;
     bool m_Left = false;
     bool m_Right = false;
     bool m_Bottom = false;
     bool m_Top = false;
     QPoint m_startPoint;
     QPoint m_old_pos;
     QLabel * m_Label;
     QPixmap m_BufferPix;
 };

 class CutRectangle : public CutShape
 {
 public:
     CutRectangle(QWidget * parent = nullptr);
     ~CutRectangle();

 protected:
     //CutShape
     virtual bool paintInit(QPaintEvent *, QPaintDevice *) Q_DECL_OVERRIDE;
     virtual QPainterPath Region() Q_DECL_OVERRIDE;
 };

 class CutRound : public CutShape
 {
 public:
     CutRound(QWidget * parent = nullptr);
     ~CutRound();

 protected:
     //CutShape
     virtual bool paintInit(QPaintEvent *, QPaintDevice *) Q_DECL_OVERRIDE;
     virtual QPainterPath Region() Q_DECL_OVERRIDE;

 private:
 };

 class BackgroundWidget : public QWidget
 {
 public:
     BackgroundWidget(QWidget * parent = nullptr, ShapeType type = Round);
     ~BackgroundWidget();

 public:
     void PictureLoadFinished();

 protected:
     virtual void paintEvent(QPaintEvent *) Q_DECL_OVERRIDE;

 private:
     ShapeType m_Type;
     CutShape * m_CutShape = nullptr;
 };

 class PicturePreviewPanel : public QWidget
 {
     Q_OBJECT

 public:
     PicturePreviewPanel(QWidget * parent = nullptr);
     ~PicturePreviewPanel();

 public:
     void LoadPicture(const QString & filepath);//加载图片

 protected:
     virtual bool eventFilter(QObject *, QEvent *) Q_DECL_OVERRIDE;

 private:
     void InitializeUI();
     void LoadPicture_p();

 private:
     QString m_PicturePath;
     QLabel * m_PictureContainer = nullptr;
     BackgroundWidget * m_BgWidget = nullptr;
 };

上述头文件，如果觉得麻烦了也可以不具体细看接口，只要理解了标题1下边的5个类的作用就可以了。下边我分别说下交互图形类、背景色类和显示图片类(即控件基类)这三者直接的一些关系，具体如下：

1、CutShape剪贴图基类 实现了基本的交互功能，并绘制了部分图案，主要的绘制在子类实现，通过实现paintInit接口，该接口在剪切图街基类重新绘制时调用，代码如下：

 void CutShape::paintEvent(QPaintEvent * event)
 {
     QPainter paint;
     if (m_EnableRepaint && paintInit(event, &m_BufferPix))
     {
         m_EnableRepaint = false;
         qDebug() << "event->type()" << event->type();
         m_BufferPix = QPixmap(size());
         m_BufferPix.fill(Qt::transparent);

         paint.begin(&m_BufferPix);
         QPen pen0;
         pen0.setColor(QColor(, , , ));
         pen0.setWidth();
         paint.setPen(pen0);
         paint.drawRect(border, border, width() - border * , width() - border * );

         QPen pen;
         QVector<qreal> dashes;
         qreal space = ;
         dashes <<  << space <<  << space;
         pen.setDashPattern(dashes);
         pen.setColor(Qt::white);

         paint.setPen(pen);
         int x_pos = (int)width() / 3.0;
         int y_pos = (int)height() / 3.0;
         paint.drawLine(x_pos, border, x_pos, height() -  * border);
         paint.drawLine( * x_pos, border,  * x_pos, height() -  * border);
         paint.drawLine(border, y_pos, width() -  * border, y_pos);
         paint.drawLine(border,  * y_pos, width() -  * border,  * y_pos);
         paint.end();
     }
     paint.begin(this);
     paint.drawPixmap(rect(), m_BufferPix);
     paint.end();
 }

上边是主要的绘制过程，关于剪切图形的交互功能，我给出具体的大姨妈，就不仔细讲解功能了，代码有些长，如下：

 void CutShape::mousePressEvent(QMouseEvent * event)
 {
     m_startPoint = event->pos();
     m_MouseDown = event->button() == Qt::LeftButton;
 }

 void CutShape::mouseMoveEvent(QMouseEvent * event)
 {
     QPoint dragPoint = event->pos();
     if (!parentWidget()->rect().contains(mapToParent(dragPoint)))
     {
         return;
     }
     int x = event->x();
     int y = event->y();
     if (m_MouseDown)
     {
         if (m_Left == false && m_Right == false
             && m_Bottom == false && m_Top == false)
         {
             QPoint p = QPoint((pos().x() + dragPoint.x() - m_startPoint.x()), (pos().y() + dragPoint.y() - m_startPoint.y()));
             QPoint dragEndge = p;
             dragEndge.setX(dragEndge.x() + rect().width());
             dragEndge.setY(dragEndge.y() + rect().height());
             p.setX(p.x() <  ?  : p.x());
             p.setX(dragEndge.x() > parentWidget()->width() ? parentWidget()->width() - rect().width() : p.x());
             p.setY(p.y() <  ?  : p.y());
             p.setY(dragEndge.y() > parentWidget()->height() ? parentWidget()->height() - rect().height() : p.y());
             move(p);
         }
         else
         {
             bool ignore = false;
             QRect g = getResizeGem(geometry(), dragPoint, ignore);
             if (parentWidget()->rect().contains(g))
                 setGeometry(g);
             if (ignore == false)
             {
                 m_startPoint = QPoint(!m_Right ? m_startPoint.x() : event->x(), !m_Bottom ? m_startPoint.y() : event->y());
             }
         }
     }
     else
     {
         QRect r = rect();
         m_Left = qAbs(x - r.left()) < ;
         m_Right = qAbs(x - r.right()) < ;
         m_Bottom = qAbs(y - r.bottom()) < ;
         m_Top = qAbs(y - r.top()) < ;
         bool lorr = m_Left | m_Right;
         bool torb = m_Top | m_Bottom;
         if (lorr && torb)
         {
             if ((m_Left && m_Top) || (m_Right && m_Bottom))
             {
                 setCursor(Qt::SizeFDiagCursor);
             }
             else
                 setCursor(Qt::SizeBDiagCursor);
         }
         else if (lorr)
             setCursor(Qt::SizeHorCursor);
         else if (torb)
             setCursor(Qt::SizeVerCursor);
         else
         {
             setCursor(Qt::SizeAllCursor);
             m_Bottom = m_Left = m_Right = m_Top = false;
         }
     }
 }

 void CutShape::mouseReleaseEvent(QMouseEvent * event)
 {
     m_MouseDown = false;
 }

 void CutShape::resizeEvent(QResizeEvent *event)
 {
     m_EnableRepaint = true;
     update();

     QWidget::resizeEvent(event);
 }

 QRect CutShape::getResizeGem(QRect oldgeo, QPoint mousePoint, bool & ignore)
 {
     QRect g = oldgeo;
     bool lorr = m_Left | m_Right;
     bool torb = m_Top | m_Bottom;
     int dx = mousePoint.x() - m_startPoint.x();
     int dy = mousePoint.y() - m_startPoint.y();
     ignore = false;
     if (lorr && torb)
     {
         int maxLen = qMax(qAbs(dx), qAbs(dy));
         if (m_Left && m_Top && dx*dy > )
         {
             g.setLeft(dx >  ? g.left() + maxLen : g.left() - maxLen);
             g.setTop(dy >  ? g.top() + maxLen : g.top() - maxLen);
         }
         else if (m_Right && m_Top && dx * dy < )
         {
             g.setRight(dx >  ? g.right() + maxLen : g.right() - maxLen);
             g.setTop(dy >  ? g.top() + maxLen : g.top() - maxLen);
         }
         else if (m_Right && m_Bottom)
         {
             if (dx * dy > )
             {
                 g.setRight(dx >  ? g.right() + maxLen : g.right() - maxLen);
                 g.setBottom(dy >  ? g.bottom() + maxLen : g.bottom() - maxLen);
             }
             else if (dx ==  && dy !=
                 /*|| dx != 0 && dy == 0*/)
             {
                 ignore = true;
             }
         }
         else if (m_Left && m_Bottom && dx*dy < )
         {
             g.setLeft(dx >  ? g.left() + maxLen : g.left() - maxLen);
             g.setBottom(dy >  ? g.bottom() + maxLen : g.bottom() - maxLen);
         }

         return g;
     }
     else if (lorr)
     {
         if (m_Left)
             g.setLeft(g.left() + dx);
         if (m_Right)
             g.setRight(g.right() + dx);
         int len = g.width() - oldgeo.width();
         int intHight = (int)len / 2.0;

         g.setTop(g.top() - intHight);
         g.setBottom(g.bottom() + len - intHight);
     }
     else if (torb)
     {
         if (m_Bottom)
             g.setBottom(g.bottom() + dy);
         if (m_Top)
             g.setTop(g.top() + dy);
         int dheigt = g.height() - oldgeo.height();
         int intWidth = (int)dheigt / 2.0;

         g.setLeft(g.left() - intWidth);
         g.setRight(g.right() + dheigt - intWidth);
     }
     else
     {
         ignore = true;
     }
     return g;
 }

2、BackgroundWidget背景色窗口，该窗口作为剪切窗口的父类窗口，但是没有布局，目的就是可以让剪切窗口自由的移动，并保持在背景色窗口之上，当背景色窗口重新绘制的时候，只绘制除剪切窗口以外的部分。这样就实现了剪切窗口是透明的但是其余部分都是半透明的，代码如下：

 void BackgroundWidget::paintEvent(QPaintEvent *)
 {
     QPainterPath painterPath;
     QPainterPath p;
     p.addRect(x(), y(), rect().width(), rect().height());
     if (m_CutShape)
     {
         painterPath.addPath(m_CutShape->CutRegion().translated(m_CutShape->pos()));
     }
     QPainterPath drawPath = p.subtracted(painterPath);

     QPainter paint(this);
     paint.setOpacity(0.5);
     paint.fillPath(drawPath, QBrush(Qt::black));
 }

3、PicturePreviewPanel图片上传控件基类，当图片加载后，需要重置背景色窗口的大小，以便覆盖到图片之上，代码如下：

 bool PicturePreviewPanel::eventFilter(QObject * watched, QEvent * event)
 {
     if (watched == m_PictureContainer)
     {
         if (event->type() == QEvent::Resize)
         {
             LoadPicture_p();
             if (m_BgWidget)
             {
                 m_BgWidget->resize(m_PictureContainer->size());
             }
         }
     }
     return QWidget::eventFilter(watched, event);
 }

之所以需要重新加载图片是，放置图片因为拖拉而失真，图片的加载的加载代码如下：

 void PicturePreviewPanel::LoadPicture_p()
 {
     QPixmap picture;
     picture.load(m_PicturePath);
     if (!picture.isNull())
     {
         picture = picture.scaled(m_PictureContainer->width(), m_PictureContainer->height());
         m_PictureContainer->setPixmap(picture);
         m_BgWidget->PictureLoadFinished();
     }
 }

好了，有了上边的代码之后，这个图片上传空间的基本交互功能就完成了，点击保存截取图片，可以使用剪贴图基类的CutRegion方法获取剪贴的路径，并保存成指定图片格式。效果如图2所示

图2 效果展示

实例代码下载：http://download.csdn.net/detail/qq_30392343/9581238

如果您觉得文章不错，不妨给个打赏，写作不易，感谢各位的支持。您的支持是我最大的动力，谢谢！！！ 

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奋斗中的无名小卒。。。