Python+PyQt5製作一個圖片檢視器

# coding:utf-8
import sys

from PyQt5.QtCore import QRect, QRectF, QSize, Qt
from PyQt5.QtGui import QPainter, QPixmap, QWheelEvent
from PyQt5.QtWidgets import (QApplication, QGraphicsItem, QGraphicsPixmapItem,
                             QGraphicsScene, QGraphicsView)


class ImageViewer(QGraphicsView):
    """ 圖片檢視器 """

    def __init__(self, parent=None):
        super().__init__(parent=parent)
        self.zoomInTimes = 0
        self.maxZoomInTimes = 22

        # 建立場景
        self.graphicsScene = QGraphicsScene()

        # 圖片
        self.pixmap = QPixmap(r'D:hzz圖片硝子硝子 (2).jpg')
        self.pixmapItem = QGraphicsPixmapItem(self.pixmap)
        self.displayedImageSize = QSize(0, 0)

        # 初始化小部件
        self.__initWidget()

    def __initWidget(self):
        """ 初始化小部件 """
        self.resize(1200, 900)

        # 隱藏卷軸
        self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)

        # 以滑鼠所在位置為錨點進行縮放
        self.setTransformationAnchor(self.AnchorUnderMouse)

        # 平滑縮放
        self.pixmapItem.setTransformationMode(Qt.SmoothTransformation)
        self.setRenderHints(QPainter.Antialiasing |
                            QPainter.SmoothPixmapTransform)

        # 設定場景
        self.graphicsScene.addItem(self.pixmapItem)
        self.setScene(self.graphicsScene)

    def wheelEvent(self, e: QWheelEvent):
        """ 捲動滑鼠滾輪縮放圖片 """
        if e.angleDelta().y() > 0:
            self.zoomIn()
        else:
            self.zoomOut()

    def resizeEvent(self, e):
        """ 縮放圖片 """
        super().resizeEvent(e)

        if self.zoomInTimes > 0:
            return

        # 調整圖片大小
        ratio = self.__getScaleRatio()
        self.displayedImageSize = self.pixmap.size()*ratio
        if ratio < 1:
            self.fitInView(self.pixmapItem, Qt.KeepAspectRatio)
        else:
            self.resetTransform()

    def setImage(self, imagePath: str):
        """ 設定顯示的圖片 """
        self.resetTransform()

        # 重新整理圖片
        self.pixmap = QPixmap(imagePath)
        self.pixmapItem.setPixmap(self.pixmap)

        # 調整圖片大小
        self.setSceneRect(QRectF(self.pixmap.rect()))
        ratio = self.__getScaleRatio()
        self.displayedImageSize = self.pixmap.size()*ratio
        if ratio < 1:
            self.fitInView(self.pixmapItem, Qt.KeepAspectRatio)

    def resetTransform(self):
        """ 重置變換 """
        super().resetTransform()
        self.zoomInTimes = 0
        self.__setDragEnabled(False)

    def __isEnableDrag(self):
        """ 根據圖片的尺寸決定是否啟動拖拽功能 """
        v = self.verticalScrollBar().maximum() > 0
        h = self.horizontalScrollBar().maximum() > 0
        return v or h

    def __setDragEnabled(self, isEnabled: bool):
        """ 設定拖拽是否啟動 """
        self.setDragMode(
            self.ScrollHandDrag if isEnabled else self.NoDrag)

    def __getScaleRatio(self):
        """ 獲取顯示的影象和原始影象的縮放比例 """
        if self.pixmap.isNull():
            return 1

        pw = self.pixmap.width()
        ph = self.pixmap.height()
        rw = min(1, self.width()/pw)
        rh = min(1, self.height()/ph)
        return min(rw, rh)

    def fitInView(self, item: QGraphicsItem, mode=Qt.KeepAspectRatio):
        """ 縮放場景使其適應視窗大小 """
        super().fitInView(item, mode)
        self.displayedImageSize = self.__getScaleRatio()*self.pixmap.size()
        self.zoomInTimes = 0

    def zoomIn(self, viewAnchor=QGraphicsView.AnchorUnderMouse):
        """ 放大影象 """
        if self.zoomInTimes == self.maxZoomInTimes:
            return

        self.setTransformationAnchor(viewAnchor)

        self.zoomInTimes += 1
        self.scale(1.1, 1.1)
        self.__setDragEnabled(self.__isEnableDrag())

        # 還原 anchor
        self.setTransformationAnchor(self.AnchorUnderMouse)

    def zoomOut(self, viewAnchor=QGraphicsView.AnchorUnderMouse):
        """ 縮小影象 """
        if self.zoomInTimes == 0 and not self.__isEnableDrag():
            return

        self.setTransformationAnchor(viewAnchor)

        self.zoomInTimes -= 1

        # 原始影象的大小
        pw = self.pixmap.width()
        ph = self.pixmap.height()

        # 實際顯示的影象寬度
        w = self.displayedImageSize.width()*1.1**self.zoomInTimes
        h = self.displayedImageSize.height()*1.1**self.zoomInTimes

        if pw > self.width() or ph > self.height():
            # 在視窗尺寸小於原始影象時禁止繼續縮小影象比視窗還小
            if w <= self.width() and h <= self.height():
                self.fitInView(self.pixmapItem)
            else:
                self.scale(1/1.1, 1/1.1)
        else:
            # 在視窗尺寸大於影象時不允許縮小的比原始影象小
            if w <= pw:
                self.resetTransform()
            else:
                self.scale(1/1.1, 1/1.1)

        self.__setDragEnabled(self.__isEnableDrag())

        # 還原 anchor
        self.setTransformationAnchor(self.AnchorUnderMouse)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = ImageViewer()
    w.show()
    sys.exit(app.exec_())