像素图上的QCustomPlot绘图点

Question

我正在尝试了解QcustomPlot图层的工作原理。

我想在网格上绘制一个像素图，然后在其上方绘制交叉点。

这是我的代码：

QString file_name;
QImage image;

ui->grid->addLayer("layer1", "main"); //above "main"
ui->grid->setCurrentLayer("layer1");

QPixmap pixels = QPixmap::fromImage(blah blah);
_pixmap->setVisible(true); //_pixmap its a member field
_pixmap->setScaled(true);
_pixmap->setPixmap(pixels);

double left_x = getLeftX();
double right_x = getRightX();
double top_y = getTopY();
double bottom_y = getBottomY();

_pixmap->topLeft->setCoords(left_x, bottom_y);
_pixmap->bottomRight->setCoords(right_x, top_y);

ui->grid->layer("layer1")->replot();

ui->grid->addLayer("layer2", "layer1"); // above "layer1"
ui->grid->setCurrentLayer("layer2");

QVector<double> x;
QVector<double> y;

x.push_back(3);
y.push_back(2);

ui->grid->graph(0)->setData(x,y);

ui->grid->layer("layer2")->replot();

仅绘制像素图，如果我在注释上放置像素图replot，则仅绘制point（3,2）。

我错过了什么吗？