將widget存成圖檔

#include <QApplication>
#include <QLabel>
#include <QTextCodec>
#include <QRgb>

int main(int argc, char *argv[]) {
  QApplication app(argc, argv);

  QTextCodec *codec = QTextCodec::codecForName("Big5-ETen");

  QLabel *label = new QLabel;
  label->setText(codec->toUnicode("<center><h1>Qt4 學習筆記</h1>~yycking.blogspot.com</center>"));

  label->setStyleSheet("QLabel { background-color: white; }");
  label->adjustSize();

  label->show();

  QImage image = QPixmap::grabWidget(label).toImage();
  image = image.convertToFormat(QImage::Format_Indexed8);

  QVector<QRgb> indexs=image.colorTable();
  for (int i = 0; i < indexs.size(); ++i) {
      int r=qRed(indexs[i]);
      int g=qGreen(indexs[i]);
      int b=qBlue(indexs[i]);
      int a=qGray(indexs[i]);
      indexs[i]=qRgba(r,g,b,255-a);
   }

  image.setColorTable(indexs);
  image.save("somefile.PNG");

  return app.exec();
}

這個方法只簡易的將Gray代替alpha而已的圖