little tips of painter.drawRect in Qt

一个QImage或QPixmap新建变量时，第一次填充图片时设置的宽高正常（fill），其后的绘制操作（draw）则会在绘制的矩形底边和右边加上painter.pen().width()

在下面代码17行设置端点查看内存可以直观看到只在右边和底边++

// 1.  生成掩码图
    const int width = 32;
    const int height = 20;
    QImage maskImg(width, height, QImage::Format_Mono);
    QPainter maskPainter(&maskImg);
    //
    maskPainter.setPen(QPen(Qt::white, 0));
    maskPainter.setBrush(Qt::white);
    maskPainter.drawRect(0, 0, width, height);
    maskPainter.setPen(QPen(Qt::black, 0));
    maskPainter.setBrush(Qt::black);
    maskPainter.drawRect(16, -16, width, height);
    maskPainter.setPen(QPen(Qt::black, 0));
    maskPainter.setBrush(Qt::black);
    maskPainter.drawRect(16, 16, 2, 3);

    maskImg.save("/home/lt47/Desktop/ORIGIN.jpg");
    qDebug() << maskImg.byteCount();
    qDebug() << maskImg.bytesPerLine();
    QRgb b = maskImg.pixel(16,20);
    qDebug() << qRed(b) << qGreen(b) << qBlue(b);
    QRgb ww = maskImg.pixel(15,20);
    qDebug() << qRed(ww) << qGreen(ww) << qBlue(ww);