按住鼠标左键画框，裁切画面并局部放大，可以用来生成ROI

 1、在QtDesigner中创建ui文件，命名为crop.ui：

2、自定义脚本ImageLabel.py ：

from PySide6.QtCore import Qt, QRect, Signal, QPoint
from PySide6.QtGui import QPixmap, QPainter, QPen, QColor
from PySide6.QtWidgets import QLabelclass ImageLabel(QLabel):src_info = Signal(str)crop_info = Signal(str)show_info = Signal(str)def __init__(self, parent=None):super().__init__(parent)self.scale = 1.0  # 显示比例，其含义为当前的显示窗口的每个像素代表原始图几个像素self.src_width = 1self.src_height = 1self.showing_pixmap = QPixmap()  # 当前显示的图像内容(从原图原比例裁切而来）self.scaled_image = QPixmap()  # 当前显示的图像内容（经过缩放适应窗口的）self.scaled_image_x0 = 0  # 显示内容的x起点self.scaled_image_y0 = 0  # 显示内容的y起点self.erase = False  # 擦除已有的方框self.start_pos = QPoint()  # 鼠标起始点self.end_pos = QPoint()  # 鼠标结束点self.show_rect = QRect(0, 0, 1, 1)  # 显示窗口维度的方框self.crop_rect = QRect(0, 0, 1, 1)  # 实际像素维度的方框# 重新定义鼠标按下事件def mousePressEvent(self, event):if event.button() == Qt.LeftButton:self.start_pos = event.position().toPoint()self.erase = False# 重新定义鼠标移动事件def mouseMoveEvent(self, event):if self.start_pos:self.end_pos = event.position().toPoint()self.show_rect = QRect(self.start_pos, self.end_pos)self.update()# 重新定义鼠标松开事件def mouseReleaseEvent(self, event):if event.button() == Qt.LeftButton:self.end_pos = event.position().toPoint()self.show_rect = QRect(self.start_pos, self.end_pos)self.erase = True  # 这一行决定了松开鼠标后方框是否擦除self.normalize_rect()  # 将方框参数转成正数self.update()self.crop_image(self.showing_pixmap, self.show_rect)  # 裁切图像# 重新定义绘画事件def paintEvent(self, event):super().paintEvent(event)painter = QPainter(self)if not self.erase:  # 不擦除painter.setPen(QPen(QColor(255, 0, 0, 255), 1, Qt.SolidLine))else:  # 擦除（用透明色画一遍）painter.setPen(QPen(QColor(0, 0, 0, 0), 2, Qt.SolidLine))painter.drawRect(self.show_rect)# 将得到的方框的长宽尺寸转换成正数def normalize_rect(self):x = self.show_rect.x()y = self.show_rect.y()width = self.show_rect.width()height = self.show_rect.height()if width < 0:x += widthwidth = abs(width)if height < 0:y += heightheight = abs(height)# 最小方框self.show_rect = QRect(x, y, max(width, 3), max(height, 3))# 裁切并显示画面def crop_image(self, real_pixmap, showing_rect):  # 注意：pixmap是需要显示的真实像素维度的图像，rect是鼠标在屏幕显示维度上的方框# 将需要显示的图像进行满幅不变形缩放，并存储为显示图像self.scaled_image = real_pixmap.scaled(self.width(), self.height(), Qt.KeepAspectRatio,Qt.SmoothTransformation)# 显示倍率，含义为显示的窗口中，每像素相当于几个实际的像素self.scale = float(real_pixmap.width() / self.scaled_image.width())# 坐标变换，当在像素窗口中画方框，映射到显示图像中的相对坐标self.scaled_image_x0 = (self.width() - self.scaled_image.width()) / 2self.scaled_image_y0 = (self.height() - self.scaled_image.height()) / 2# 用以在实际像素的原图中裁切的方框self.crop_rect = QRect((showing_rect.x() - self.scaled_image_x0) * self.scale,(showing_rect.y() - self.scaled_image_y0) * self.scale,(showing_rect.width()) * self.scale,(showing_rect.height()) * self.scale)# 裁切到的用以显示的图像self.showing_pixmap = self.showing_pixmap.copy(self.crop_rect)# 再次缩放裁切到的的图像self.scaled_image = self.showing_pixmap.scaled(self.width(), self.height(), Qt.KeepAspectRatio,Qt.SmoothTransformation)  # 将需要显示的图像进行满幅不变形缩放，并存储为显示图像self.setPixmap(self.scaled_image)  # 显示图像self.setAlignment(Qt.AlignCenter)  # 居中显示# 再次计算显示倍率self.scale = self.showing_pixmap.height() / self.scaled_image.height()self.crop_info.emit(f'裁切到的尺寸：{str(self.showing_pixmap.width())} * {str(self.showing_pixmap.height())}')self.show_info.emit(f'显示像素：{str(self.scaled_image.width())} * {str(self.scaled_image.height())}，显示倍率：{self.scale}')# 初始化，设置原图像def set_src(self, pixmap):self.src_width = pixmap.width()self.src_height = pixmap.height()self.showing_pixmap = pixmap.copy()# 满幅裁切self.crop_rect = QRect(0, 0, self.width(), self.height())self.crop_image(self.showing_pixmap, self.crop_rect)self.src_info.emit(f'原图尺寸：{str(self.src_width)} * {str(self.src_height)}')

3、在QtDesigner中添加“提升为”的自定义脚本，并且将显示用的窗口提升：

4、用pyui工具将ui文件生成py文件，并编写主程序：

# encoding: utf-8from PySide6.QtCore import QObject
from PySide6.QtWidgets import QApplication, QMainWindow
from PySide6.QtGui import QPixmap, Qt
import sysimport crop_rc  # 导入需要显示的画面# 定义需要显示的画面类
class MainWindow(QMainWindow, crop_rc.Ui_MainWindow):def __init__(self):super().__init__()# 系统的初始化
def start_todo():pass# #############################主程序##################################
if __name__ == '__main__':app = QApplication(sys.argv)# #######################项目级别的定义#############################class UI(QObject):  # 将项目定义为QObject，用来管理项目级别的信号和变量# ###########__init__###############def __init__(self):super().__init__()# ########################本项目的实例化############################ui = UI()  # 项目实例化# ########################实例化画面###############################window1 = MainWindow()  # 画面实例化window1.show()  # 显示画面window1.setupUi(window1)  # 画面初始化# ###########################信号的连接和槽函数###################### “保存文件”按钮点击的槽函数def window1_btn_save_clicked():pass# “保存文件”按钮点击的连接window1.btn_save.clicked.connect(window1_btn_save_clicked)# “恢复原图”按钮点击的槽函数def window1_btn_refresh_clicked():window1.label_show.set_src(ui.src_img)    # 设置并显示原始图像# “恢复原图”按钮点击的连接window1.btn_refresh.clicked.connect(window1_btn_refresh_clicked)# 几个信息显示标签的文字更新槽和连接def src_info_changed(txt):window1.src_info.setText(txt)def crop_info_changed(txt):window1.crop_info.setText(txt)def show_info_changed(txt):window1.show_info.setText(txt)window1.label_show.src_info.connect(src_info_changed)window1.label_show.crop_info.connect(crop_info_changed)window1.label_show.show_info.connect(show_info_changed)# ###########################系统的初始化#######################start_todo()ui.src_img = QPixmap('../PYS/9.png')  # 读取和定义原图像文件window1.label_show.set_src(ui.src_img)  # 设置并显示原图像sys.exit(app.exec())