graphics_view_zoom.py

# -*- coding: utf-8 -*-

import sys
import os
import os.path

from PySide2 import QtCore, QtGui, QtWidgets
from PySide2.QtUiTools import QUiLoader

ZOOM_MIN = -0.5
ZOOM_MAX = 2


class UISample(QtWidgets.QDialog):

    def __init__(self, parent=None):

        super(UISample, self).__init__((parent))

        self.view = NodeView()
        layout  = QtWidgets.QVBoxLayout()
        self.setLayout(layout)
        layout.addWidget(self.view)

        self.scene = NodeScene()
        self.view.setScene(self.scene)

        item = self.scene.addEllipse(150, 150, 200, 100)
        item.setBrush(QtGui.QBrush(QtGui.QColor('pink')))


class NodeView(QtWidgets.QGraphicsView):

    def __init__(self, parent=None):
        super(NodeView, self).__init__(parent)

    def wheelEvent(self, e):
        delta = e.delta()
        adjust = (delta / 120) * 0.1
        self.set_zoom(adjust)

    def set_zoom(self, value):

        scale = 0.0
        # 今のズーム率 指定外にはならないようにする
        zoom = self.get_zoom()
        if ZOOM_MIN >= zoom:
            if value < 0.0:
                return
        if ZOOM_MAX <= zoom:
            if value > 0.0:
                return
        scale = 0.9 if value < 0.0 else 1.1
        self.scale(scale, scale)

    def get_zoom(self):
        transform = self.transform()
        cur_scale = (transform.m11(), transform.m22())
        return float('{:0.2f}'.format(cur_scale[0] - 1.0))


class NodeScene(QtWidgets.QGraphicsScene):

    sel_item = None

    def __init__(self, parent=None):
        super(NodeScene, self).__init__(parent)

    def mousePressEvent(self, e):
        if e.button() == QtCore.Qt.LeftButton:
            self.sel_item = self.itemAt(e.scenePos(), QtGui.QTransform())
            self.mouse_pos = e.scenePos()

    def mouseMoveEvent(self, e):
        if self.sel_item is not None:
            cur = e.scenePos()
            val = cur - self.mouse_pos
            self.sel_item.moveBy(val.x(),val.y())
            self.mouse_pos = cur

    def viewer(self):
        return self.views()[0] if self.views() else None

    def mouseReleaseEvent(self, e):
        self.mouse_pos = None
        self.sel_item = None


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    a = UISample()
    a.show()
    sys.exit(app.exec_())