QGraphicsView 实现图片裁剪功能

本教程实现了图片显示、滚轮放大缩小图片、鼠标中键移动图片、画框裁剪图片功能。

界面程序

from PyQt5.QtCore import QSize, Qt, QRect
from PyQt5.QtGui import QColor
from PyQt5.QtWidgets import QApplication, QDialog, QGridLayout, QPushButton, QSpacerItem, QSizePolicy

try:
    from .graphics import GraphicsView, GraphicsPixmapItem
except:
    from graphics import GraphicsView, GraphicsPixmapItem


class Form(QDialog):
    def __init__(self):
        super(Form, self).__init__()
        self.resize(1024, 768)

        self.picture = r'test.png'
        self.init_ui()
        # 视图背景颜色
        self.graphicsView.setBackgroundBrush(QColor(28, 31, 34))
        self.graphicsView.save_signal.connect(self.pushButton_save.setEnabled)
        self.pushButton_cut.clicked.connect(self.pushButton_cut_clicked)
        self.pushButton_save.clicked.connect(self.pushButton_save_clicked)
        # image_item = GraphicsPolygonItem()
        # image_item.setFlag(QGraphicsItem.ItemIsMovable)
        # self.scene.addItem(image_item)

    def init_ui(self):
        self.gridLayout = QGridLayout(self)
        self.pushButton_cut = QPushButton('cut', self)
        self.pushButton_cut.setCheckable(True)
        self.pushButton_cut.setMaximumSize(QSize(100, 16777215))
        self.gridLayout.addWidget(self.pushButton_cut, 0, 0, 1, 1)
        self.pushButton_save = QPushButton('save', self)
        self.pushButton_save.setEnabled(False)
        self.gridLayout.addWidget(self.pushButton_save, 1, 0, 1, 1)
        spacerItem = QSpacerItem(20, 549, QSizePolicy.Minimum, QSizePolicy.Expanding)
        self.gridLayout.addItem(spacerItem, 2, 0, 1, 1)
        self.graphicsView = GraphicsView(self.picture, self)
        self.graphicsView.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.graphicsView.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
        self.gridLayout.addWidget(self.graphicsView, 0, 1, 3, 1)

    def pushButton_cut_clicked(self):
        if self.graphicsView.image_item.is_start_cut:
            self.graphicsView.image_item.is_start_cut = False
            self.graphicsView.image_item.setCursor(Qt.ArrowCursor)  # 箭头光标
        else:
            self.graphicsView.image_item.is_start_cut = True
            self.graphicsView.image_item.setCursor(Qt.CrossCursor)  # 十字光标

    def pushButton_save_clicked(self):
        rect = QRect(self.graphicsView.image_item.start_point.toPoint(),
                     self.graphicsView.image_item.end_point.toPoint())
        new_pixmap = self.graphicsView.image_item.pixmap().copy(rect)
        new_pixmap.save(r'test.png')


if __name__ == '__main__':
    import sys

    app = QApplication(sys.argv)
    form = Form()
    form.show()
    app.exec_()

重构QGraphicsView和QGraphicsPixmapItem

from PyQt5.QtCore import QRectF, Qt, pyqtSignal
from PyQt5.QtGui import QColor, QPixmap, QPen
from PyQt5.QtWidgets import QGraphicsView, QGraphicsPixmapItem, QGraphicsScene, QGraphicsItem


class GraphicsView(QGraphicsView):
    save_signal = pyqtSignal(bool)

    def __init__(self, picture, parent=None):
        super(GraphicsView, self).__init__(parent)

        # 设置放大缩小时跟随鼠标
        self.setTransformationAnchor(QGraphicsView.AnchorUnderMouse)
        self.setResizeAnchor(QGraphicsView.AnchorUnderMouse)

        self.scene = QGraphicsScene()
        self.setScene(self.scene)

        self.image_item = GraphicsPixmapItem(QPixmap(picture))
        self.image_item.setFlag(QGraphicsItem.ItemIsMovable)
        self.scene.addItem(self.image_item)

        size = self.image_item.pixmap().size()
        # 调整图片在中间
        self.image_item.setPos(-size.width() / 2, -size.height() / 2)
        self.scale(0.1, 0.1)

    def wheelEvent(self, event):
        '''滚轮事件'''
        zoomInFactor = 1.25
        zoomOutFactor = 1 / zoomInFactor

        if event.angleDelta().y() > 0:
            zoomFactor = zoomInFactor
        else:
            zoomFactor = zoomOutFactor

        self.scale(zoomFactor, zoomFactor)

    def mouseReleaseEvent(self, event):
        '''鼠标释放事件'''
        # print(self.image_item.is_finish_cut, self.image_item.is_start_cut)
        if self.image_item.is_finish_cut:
            self.save_signal.emit(True)
        else:
            self.save_signal.emit(False)


class GraphicsPixmapItem(QGraphicsPixmapItem):
    save_signal = pyqtSignal(bool)

    def __init__(self, picture, parent=None):
        super(GraphicsPixmapItem, self).__init__(parent)

        self.setPixmap(picture)
        self.is_start_cut = False
        self.current_point = None
        self.is_finish_cut = False

    def mouseMoveEvent(self, event):
        '''鼠标移动事件'''
        self.current_point = event.pos()
        if not self.is_start_cut or self.is_midbutton:
            self.moveBy(self.current_point.x() - self.start_point.x(),
                        self.current_point.y() - self.start_point.y())
            self.is_finish_cut = False
        self.update()

    def mousePressEvent(self, event):
        '''鼠标按压事件'''
        super(GraphicsPixmapItem, self).mousePressEvent(event)
        self.start_point = event.pos()
        self.current_point = None
        self.is_finish_cut = False
        if event.button() == Qt.MidButton:
            self.is_midbutton = True
            self.update()
        else:
            self.is_midbutton = False
            self.update()

    def paint(self, painter, QStyleOptionGraphicsItem, QWidget):
        super(GraphicsPixmapItem, self).paint(painter, QStyleOptionGraphicsItem, QWidget)
        if self.is_start_cut and not self.is_midbutton:
            # print(self.start_point, self.current_point)
            pen = QPen(Qt.DashLine)
            pen.setColor(QColor(0, 150, 0, 70))
            pen.setWidth(3)
            painter.setPen(pen)
            painter.setBrush(QColor(0, 0, 255, 70))
            if not self.current_point:
                return
            painter.drawRect(QRectF(self.start_point, self.current_point))
            self.end_point = self.current_point
            self.is_finish_cut = True

成果