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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 // 1.  生成掩码图 2     const int width = 32; 3     const int height = 20; 4     QImage maskImg(width, height, QImage::Format_Mono); 5     QPainter maskPainter(&maskImg); 6     // 7     maskPainter.setPen(QPen(Qt::white, 0)); 8     maskPainter.setBrush(Qt::white); 9     maskPainter.drawRect(0, 0, width, height);10     maskPainter.setPen(QPen(Qt::black, 0));11     maskPainter.setBrush(Qt::black);12     maskPainter.drawRect(16, -16, width, height);13     maskPainter.setPen(QPen(Qt::black, 0));14     maskPainter.setBrush(Qt::black);15     maskPainter.drawRect(16, 16, 2, 3);16 17     maskImg.save("/home/lt47/Desktop/ORIGIN.jpg");18     qDebug() << maskImg.byteCount();19     qDebug() << maskImg.bytesPerLine();20     QRgb b = maskImg.pixel(16,20);21     qDebug() << qRed(b) << qGreen(b) << qBlue(b);22     QRgb ww = maskImg.pixel(15,20);23     qDebug() << qRed(ww) << qGreen(ww) << qBlue(ww);

 

little tips of painter.drawRect in Qt