使用PyQt的QLabel组件实现选定目标框功能的方法示例

from PyQt5.QtWidgets import QLabel
from PyQt5.QtCore import Qt,QRect
from PyQt5.QtGui import QPainter,QPen

class Label(QLabel):
  x0=0
  y0=0
  x1=0
  y1=0
  open_mouse_flag=False
  select_roi_flag=False
  draw_roi_flag=False
  clear_flag=False
  rect = QRect()

  #按下鼠标
  def mousePressEvent(self, event):
    if self.open_mouse_flag is True:
      self.select_roi_flag=True
      self.x0=event.x()
      self.y0=event.y()

  #释放鼠标
  def mouseReleaseEvent(self, event):
    self.select_roi_flag=False

  #移动鼠标
  def mouseMoveEvent(self, event):
    if self.select_roi_flag is True:
      self.x1=event.x()
      self.y1=event.y()
      if self.draw_roi_flag is True:
        self.update()

  #绘制事件
  def paintEvent(self,event):
    super().paintEvent(event)
    painter = QPainter(self)
    painter.setPen(QPen(Qt.red, 5, Qt.SolidLine))
    if self.clear_flag is True:
      self.x0=0
      self.y0=0
      self.x1=0
      self.y1=0
    self.rect = QRect(self.x0, self.y0, abs(self.x1 - self.x0), abs(self.y1 - self.y0))
    painter.drawRect(self.rect)
    self.update()   

# 清除label对象的绘制内容
def clear_label(self):
  self.label_show.clear_flag = True
  self.label_show.clear()

# 重写键盘事件
def keyPressEvent(self, QKeyEvent):
  if self.open_keyboard_flag is True:         # 当键盘事件为真的是才有键盘事件监控
    if QKeyEvent.key() == Qt.Key_S:
      self.label_show.setCursor(Qt.CrossCursor)  # 切换游标为十字型
      self.label_show.open_mouse_flag = True
      self.label_show.draw_roi_flag = True
    if QKeyEvent.key() == Qt.Key_Q:         # 按下'q'键键盘监控关闭
      self.label_show.unsetCursor()
      self.label_show.draw_roi_flag = False
      self.label_show.open_mouse_flag = False
      self.open_keyboard_flag = False