在 QGraphicsView 中启用平移/缩放

Question

我正在使用 Python 和 QtDesigner 来显示带有叠加层的相机图像。 我的主窗口可以访问相机设置，并相应地触发相机。它通过 pyQtSlot 将每个图像发送到 QGraphicsView。

如何在此 QGraphicView 中启用缩放功能？

我已阅读答案如何在 QGraphicsView 中启用平移和缩放 它对于冻结的图片效果很好，但是当我发送下一张图像时，缩放会重置。

这是我的工作代码（因此我没有尝试实现缩放）：

from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QWidget, QGraphicsPixmapItem
from PyQt5.QtGui import QImage, QPainter, QPixmap
from PyQt5.QtCore import QRectF, pyqtSlot, Qt

class Display(QGraphicsView):
    def __init__(self, parent: QWidget = None):
        super().__init__(parent)
        self._empty = True
        self.image_qt = QImage()
        self._scene = QGraphicsScene()
        self.pic = QGraphicsPixmapItem()
        self._scene.addItem(self.pic)
        self.setScene(self._scene)
        self.setAlignment(Qt.AlignCenter)

    def hasPicture(self):
        return not self._empty

    @pyqtSlot(QImage)
    def on_image_received(self, image: QImage, scale: float, x_offset: int, y_offset: int):
        # Scale the overlay, Adjust the position
        # self.image_qt = set_calque(image, scale, x_offset, y_offset)
        # not useful for a minimal example, so skip the overlay part:
        self.image_qt = image

        # Image size
        image_width = self.image_qt.width()
        image_height = self.image_qt.height()

        # Return if we don't have an image yet
        if image_width == 0 or image_height == 0:
            return

        self._empty = False
        self.pic.setPixmap(QPixmap.fromImage(self.image_qt))
        self.fitInView(QRectF(0, 0, image_width, image_height), Qt.KeepAspectRatio)
        self.update()

Answer 1

经过几次尝试，我几乎可以正常工作了：我认为缩放没有很好地集中在鼠标位置上，但我不明白为什么。

from PyQt5.QtWidgets import QGraphicsView, QGraphicsScene, QWidget, QGraphicsPixmapItem
from PyQt5.QtGui import QImage, QPainter, QPixmap
from PyQt5.QtCore import QRectF, pyqtSlot, Qt, QPoint


class Display(QGraphicsView):
    def __init__(self, parent: QWidget = None):
        super().__init__(parent)
        self._zoom = 1
        self._pt = QPoint()
        self._empty = True
        self.image_qt = QImage()
        self._scene = QGraphicsScene()
        self.pic = QGraphicsPixmapItem()
        self._scene.addItem(self.pic)
        self.setScene(self._scene)
        self.setAlignment(Qt.AlignCenter)

    def hasPicture(self):
        return not self._empty

    def wheelEvent(self, event):
        # self.pt = self.mapToScene(event.pos()).toPoint()
        self._pt = event.pos()
        if self.hasPicture():
            if event.angleDelta().y() > 0:
                factor = 1.2
                self._zoom *= factor
            else:
                factor = 0.8
                self._zoom *= factor
            if self._zoom > 0:
                self.scale(factor, factor)

    @pyqtSlot(QImage)
    def on_image_received(self, image: QImage, scale: float, x_offset: int, y_offset: int):
        # overlay the image. Scale the overlay, Adjust its position
        self.image_qt = set_calque(image, scale, x_offset, y_offset)

        # Image size
        image_width = self.image_qt.width()
        image_height = self.image_qt.height()

        # Return if we don't have an image yet
        if image_width == 0 or image_height == 0:
            return

        self._empty = False
        self.setDragMode(QGraphicsView.ScrollHandDrag)
        self.pic.setPixmap(QPixmap.fromImage(self.image_qt))
        self.fitInView()
        self.update()

    def fitInView(self, scale=True):
        rect = QRectF(self.pic.pixmap().rect())
        if not rect.isNull():
            if not self._pt.isNull() and self._zoom > 1:
                rect.moveCenter(self._pt)
            self.setSceneRect(rect)
            if self.hasPicture():
                unity = self.transform().mapRect(QRectF(0, 0, 1, 1))
                self.scale(1 / unity.width(), 1 / unity.height())
                viewrect = self.viewport().rect()
                scenerect = self.transform().mapRect(rect)
                factor = min(viewrect.width() / scenerect.width(),
                             viewrect.height() / scenerect.height())
                factor *= self._zoom
                self.scale(factor, factor)