PyQt/PySide中QPdfView子类化以支持交互式矩形绘制教程

# 定义绘图状态常量
FREE_STATE = 1        # 自由状态，未进行任何绘图操作
BUILDING_SQUARE = 2   # 正在绘制矩形
BEGIN_SIDE_EDIT = 3   # 正在编辑矩形的起始边（通常是左边）
END_SIDE_EDIT = 4     # 正在编辑矩形的结束边（通常是右边）

from PyQt5.QtWidgets import QMainWindow, QApplication, QVBoxLayout, QWidget
from PyQt5.QtPdfWidgets import QPdfView
from PyQt5.QtPdf import QPdfDocument
from PyQt5.QtCore import QPoint, QRect, QUrl
from PyQt5.QtGui import QPainter, QColor, QPen
import sys

# ... (FREE_STATE, BUILDING_SQUARE等定义)

class CustomQPdfView(QPdfView):
    def __init__(self, parent=None):
        super().__init__(parent)

        # 初始化矩形绘制的起始点和结束点
        self.begin = QPoint()
        self.end = QPoint()

        # 初始化绘图状态为自由状态
        self.state = FREE_STATE

        # 设置矩形绘制的画笔：半透明红色，宽度为2
        self.pen = QPen(QColor(255, 0, 0, 150)) 
        self.pen.setWidth(2)

        # 可选：设置组件的初始几何尺寸，如果需要的话
        # self.setGeometry(30, 30, 600, 400) 

    def paintEvent(self, event):
        super().paintEvent(event) # 首先调用父类的paintEvent，绘制PDF内容

        # 创建一个QPainter，作用于QPdfView的视口
        painter = QPainter(self.viewport())
        painter.setPen(self.pen)

        # 绘制矩形，如果起始点和结束点有效
        if not self.begin.isNull() and not self.end.isNull():
            # .normalized()确保QRect的top-left和bottom-right坐标是正确的，
            # 无论用户从哪个方向拖动鼠标
            painter.drawRect(QRect(self.begin, self.end).normalized())

    def mousePressEvent(self, event):
        # 如果已经存在一个矩形，判断是否点击到其边缘进行编辑
        if not self.begin.isNull() and not self.end.isNull():
            p = event.pos()
            rect = QRect(self.begin, self.end).normalized()

            # 检查是否接近矩形的左边或右边，提供3像素的容差
            if abs(rect.left() - p.x()) <= 3 and rect.top() <= p.y() <= rect.bottom():
                self.state = BEGIN_SIDE_EDIT
                return
            elif abs(rect.right() - p.x()) <= 3 and rect.top() <= p.y() <= rect.bottom():
                self.state = END_SIDE_EDIT
                return

        # 如果不是编辑现有矩形，则开始绘制新矩形
        self.state = BUILDING_SQUARE
        self.begin = event.pos()
        self.end = event.pos()
        # 注意：这里不需要立即调用repaint，因为mouseMoveEvent会处理后续的刷新

    def apply_event(self, event):
        if self.state == BUILDING_SQUARE:
            self.end = event.pos()
        elif self.state == BEGIN_SIDE_EDIT:
            # 仅修改x坐标以调整左边
            self.begin.setX(event.x())
        elif self.state == END_SIDE_EDIT:
            # 仅修改x坐标以调整右边
            self.end.setX(event.x())

    def mouseMoveEvent(self, event):
        if self.state != FREE_STATE: # 只有在绘