1. 需求
主要为以下需求：
- 标注框的拖拽生成
- 标注框的拖拽移动
- 标注框的拖拽缩放
- 标注框外双击自动销毁
2. 基本思路
维护一个标注框的坐标列表。主要通过创建该标注框的起始点坐标和终点坐标，实现标注框的拖拽生成；通过更新该列表，实现拖拽移动和缩放；通过置空该列表，实现双击销毁。
3. 实现
参考博客《PYQT5实现矩形框的拖动和改变大小（简易版文本框的实现）》
本代码中的图片地址img = QPixmap('./3.png')需自行更新。
from PyQt5.QtWidgets import QWidget, QApplication, QLabel
from PyQt5.QtCore import QRect, Qt
from PyQt5.QtGui import QImage, QPixmap, QPainter, QPen
import cv2
import sys
class MyLabel(QLabel):
#x0 = 0
#y0 = 0
#x1 = 0
#y1 = 0
flag = False # 是否按下鼠标
move = False # 是否进行拖拽整体移动
biggerLeft = False # 是否进行拖拽放大缩小，坐标点在标注框的左边
biggerRight = False # 是否进行拖拽放大缩小，坐标点在标注框的右边
biggerButton = False # 是否进行拖拽放大缩小，坐标点在标注框的下边
biggerTop = False # 是否进行拖拽放大缩小，坐标点在标注框的上边
rect = [] # 标注框的起始点坐标和终点坐标，形如 [start_x, start_y, end_x, end_y]
# 鼠标双击事件
def mouseDoubleClickEvent(self, event):
self.rect = []
print("双击事件发生！")
self.update()
#鼠标单击事件
def mousePressEvent(self,event):
self.flag = True
#self.x0 = event.x()
#self.y0 = event.y()
if self.rect:
# 此时已经存在标注框，再点击，则为拖拽整体移动或者放大缩小
# 整体移动：当点击坐标位于标注框内，则说明为整体移动
# 放大缩小：当点击坐标位于标注框的四条边上，则说明为放大缩小
# 框的左上角和右下角
topleft_x = min(self.rect[0], self.rect[2])
topleft_y = min(self.rect[1], self.rect[3])
buttonright_x = max(self.rect[0], self.rect[2])
buttonright_y = max(self.rect[1], self.rect[3])
# 整体移动的判定：点坐标在左上角和右下角之间
if (event.x() > topleft_x + 5) and (event.x() < buttonright_x - 5) and (event.y() > topleft_y+ 5) and (event.y() < buttonright_y - 5):
print("判定为整体移动")
self.move = True
self.preMousePosition = event.pos()
# 放大缩小的判定：点坐标在框的四条边上
# 上边，下边、左边、右边
# 当点坐标在标注框的左边时
if (event.x() > topleft_x - 5) and (event.x() < topleft_x + 5) and (event.y() > topleft_y) and (event.y() < buttonright_y):
print("判定为放大缩小，点坐标在标注框的左边上")
self.biggerLeft = True
self.preMousePosition = event.pos()
# 当点坐标在标注框的右边时
if (event.x() > buttonright_x - 5) and (event.x() < buttonright_x + 5) and (event.y() > topleft_y) and (event.y() < buttonright_y):
print("判定为放大缩小，点坐标在标注框的右边上")
self.biggerRight = True
self.preMousePosition = event.pos()
# 当点坐标在标注框的下边时
if (event.x() > topleft_x) and (event.x() < buttonright_x) and (event.y() > buttonright_y - 5) and (event.y() < buttonright_y + 5):
print("判定为放大缩小，点坐标在标注框的下边上")
self.biggerButton = True
self.preMousePosition = event.pos()
# 当点坐标在标注框的上边时
if (event.x() > topleft_x) and (event.x() < buttonright_x) and (event.y() > topleft_y - 5) and (event.y() < topleft_y + 5):
print("判定为放大缩小，点坐标在标注框的上边上")
self.biggerTop = True
self.preMousePosition = event.pos()
else:
# 如果当前没有标注框，则说明点击后开始拖拽生成标注框
# 此时，没有整体移动和放大缩小
self.move = False
self.biggerLeft = False
self.biggerRight = False
self.biggerButton = False
self.biggerTop = False
self.rect = [event.x(), event.y(), event.x(), event.y()]
#鼠标释放事件
def mouseReleaseEvent(self,event):
self.flag = False
self.biggerLeft = False
self.biggerRight = False
self.biggerButton = False
self.biggerTop = False
self.move = False
#鼠标移动事件
def mouseMoveEvent(self,event):
start_x, start_y = self.rect[0:2]
if self.flag: # 按下鼠标，开始拖拽
# 拖拽可能有三种情况
# 情况1：在已有标注框的情况下，进行放大缩小
# 情况1.1：标注框的左边
if self.biggerLeft:
print("放大缩小：左边进行x轴方向的缩放")
differ = event.pos() - self.preMousePosition
# 更新标注框
start_x, start_y, end_x, end_y = self.rect
if start_x < end_x:
start_x += differ.x()
else:
end_x += differ.x()
self.rect = [start_x, start_y, end_x, end_y]
self.preMousePosition = event.pos()
# 情况1.2：标注框的右边
elif self.biggerRight:
print("放大缩小：右边进行x轴方向的缩放")
differ = event.pos() - self.preMousePosition
# 更新标注框
start_x, start_y, end_x, end_y = self.rect
if start_x > end_x:
start_x += differ.x()
else:
end_x += differ.x()
self.rect = [start_x, start_y, end_x, end_y]
self.preMousePosition = event.pos()
# 情况1.3：标注框的下边
elif self.biggerButton:
print("放大缩小：下边进行y轴方向的缩放")
differ = event.pos() - self.preMousePosition
# 更新标注框
start_x, start_y, end_x, end_y = self.rect
if start_y > end_y:
start_y += differ.y()
else:
end_y += differ.y()
self.rect = [start_x, start_y, end_x, end_y]
self.preMousePosition = event.pos()
# 情况1.4：标注框的上边
elif self.biggerTop:
print("放大缩小：上边进行y轴方向的缩放")
differ = event.pos() - self.preMousePosition
# 更新标注框
start_x, start_y, end_x, end_y = self.rect
if start_y < end_y:
start_y += differ.y()
else:
end_y += differ.y()
self.rect = [start_x, start_y, end_x, end_y]
self.preMousePosition = event.pos()
# 情况2：在已有标注框的情况下，进行整体移动
elif self.move:
differ = event.pos() - self.preMousePosition
# 更新标注框
start_x, start_y, end_x, end_y = self.rect
start_x, start_y = start_x + differ.x(), start_y + differ.y()
end_x, end_y = end_x + differ.x(), end_y + differ.y()
self.rect = [start_x, start_y, end_x, end_y]
self.preMousePosition = event.pos()
print("整体移动")
# 情况3：做标注框
else:
#self.x1 = event.x()
#self.y1 = event.y()
self.rect = [start_x, start_y, event.x(), event.y()]
self.update()
#绘制事件
def paintEvent(self, event):
super().paintEvent(event)
if len(self.rect) == 0: return
# rect =QRect(self.x0, self.y0, abs(self.x1-self.x0), abs(self.y1-self.y0))
# 这里换成任意方向的矩形框
# 标注框的左上角和右下角坐标
x0 = min(self.rect[0], self.rect[2])
y0 = min(self.rect[1], self.rect[3])
x1 = max(self.rect[0], self.rect[2])
y1 = max(self.rect[1], self.rect[3])
width = x1 - x0
height = y1 - y0
# 矩形
rect =QRect(x0, y0, width, height)
painter = QPainter(self)
painter.setPen(QPen(Qt.red,2,Qt.SolidLine))
painter.drawRect(rect)
class Example(QWidget):
def __init__(self):
super().__init__()
self.initUI()
def initUI(self):
self.resize(675, 500)
self.move(100,50)
self.setWindowTitle('在label中绘制矩形')
self.lb = MyLabel(self) #重定义的label
# 这里直接读取图片
img = QPixmap('./3.png')
# 往显示视频的Label里 显示QImage
self.lb.setPixmap(img)
self.lb.setCursor(Qt.CrossCursor)#图片可以绘制
self.show()
if __name__ == '__main__':
app = QApplication(sys.argv)
x = Example()
sys.exit(app.exec_())