将项目打印为pdf

要了解绘画是什么样的，您必须了解QGraphicsScene::render()方法的工作原理：

void QGraphicsScene::render(QPainter *painter, const QRectF &target = QRectF(), const QRectF &source = QRectF(), Qt::AspectRatioMode aspectRatioMode = Qt::KeepAspectRatio)

Renders the source rect from scene into target, using painter. This function is useful for capturing the contents of the scene onto a paint device, such as a QImage (e.g., to take a screenshot), or for printing with QPrinter. For example:

QGraphicsScene scene;
scene.addItem(...
...
QPrinter printer(QPrinter::HighResolution);
printer.setPaperSize(QPrinter::A4);

QPainter painter(&printer);
scene.render(&painter);

If source is a null rect, this function will use sceneRect() to determine what to render. If target is a null rect, the dimensions of painter's paint device will be used.

The source rect contents will be transformed according to aspectRatioMode to fit into the target rect. By default, the aspect ratio is kept, and source is scaled to fit in target.

See also QGraphicsView::render().

在您的情况下，如果未传递源，则将复制整个sceneRect（0、0、1230、650）并将其绘制在pdf页面上，如果大小不匹配，则将缩放大小。因此，从上面可以看出，如果要打印项目，则必须将其在场景中占据的空间作为源传递，并隐藏其他项目，而目标是要绘制的位置，这涉及到计算新的根据上一个项目的打印位置。

考虑到上述情况，可能的解决方法如下：

import random

from PyQt5 import QtCore, QtGui, QtWidgets


class Gui(QtWidgets.QDialog):
    def __init__(self, parent=None):
        super(Gui, self).__init__(parent)
        self.resize(1280, 720)
        self.scene = QtWidgets.QGraphicsScene(
            0, 0, self.width() - 50, self.height() - 70
        )
        self.scene.setBackgroundBrush(QtGui.QBrush(QtCore.Qt.white))
        self.canvas = QtWidgets.QGraphicsView(self.scene)
        mainLayout = QtWidgets.QGridLayout(self)
        mainLayout.addWidget(self.canvas)

    @property
    def circleList(self):
        return [
            item
            for item in self.scene.items()
            if isinstance(item, QtWidgets.QGraphicsEllipseItem)
        ]

    def newCircle(self):
        self.scene.addEllipse(
            random.randint(100, 400),
            random.randint(100, 400),
            50 + random.random() * 200,
            50 + random.random() * 200,
        )

    def generateReport(self):
        printer = QtGui.QPdfWriter("Output.pdf")
        printer.setPageSize(QtGui.QPagedPaintDevice.A4)
        printer.setResolution(100)
        painter = QtGui.QPainter(printer)
        delta = 20
        f = painter.font()
        f.setPixelSize(delta)
        painter.setFont(f)
        # hide all items
        last_states = []
        for item in self.scene.items():
            last_states.append(item.isVisible())
            item.setVisible(False)

        target = QtCore.QRectF(0, 0, printer.width(), 0)

        for i, item in enumerate(self.circleList):
            item.setVisible(True)
            source = item.mapToScene(item.boundingRect()).boundingRect()
            target.setHeight(source.height())
            if target.bottom() > printer.height():
                printer.newPage()
                target.moveTop(0)
            self.scene.render(painter, target, source)
            f = painter.font()
            f.setPixelSize(delta)
            painter.drawText(
                QtCore.QRectF(
                    target.bottomLeft(), QtCore.QSizeF(printer.width(), delta + 5)
                ),
                "test",
            )
            item.setVisible(False)
            target.setTop(target.bottom() + delta + 20)
        # restore visibility
        for item, state in zip(self.scene.items(), last_states):
            item.setVisible(state)
        painter.end()


if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    w = Gui()
    for _ in range(200):
        w.newCircle()
    w.generateReport()
    w.show()
    sys.exit(app.exec_())