PyQt5实现图片裁剪

可以使用QPixmap和QGraphicsScene来实现图片裁剪。

首先，需要在PyQt5中导入以下模块：

from PyQt5.QtWidgets import QApplication, QGraphicsScene, QGraphicsView, QGraphicsPixmapItem, QFileDialog, QGraphicsRectItem, QGraphicsItem
from PyQt5.QtGui import QPixmap, QCursor
from PyQt5.QtCore import Qt, QRectF

接着，创建一个QGraphicsScene对象并将其设置为QGraphicsView的场景：

scene = QGraphicsScene()
view = QGraphicsView(scene)

然后，使用QFileDialog打开一张图片，将其加载到QPixmap对象中，并将该对象设置为QGraphicsPixmapItem的Pixmap：

filename, _ = QFileDialog.getOpenFileName(None, "Open Image", "", "Image Files (*.png *.jpg *.bmp)")
if filename:
    pixmap = QPixmap(filename)
    pixmap_item = QGraphicsPixmapItem(pixmap)
    scene.addItem(pixmap_item)

接下来，使用QGraphicsRectItem创建一个裁剪框，并将其添加到场景中：

rect_item = QGraphicsRectItem()
rect_item.setPen(Qt.red)
rect_item.setFlags(QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable)
rect_item.setZValue(1)
scene.addItem(rect_item)

为了使裁剪框可以拖动和缩放，需要在鼠标按下事件和鼠标移动事件中添加代码：

def mousePressEvent(event):
    if event.button() == Qt.LeftButton:
        rect_item.setFlags(QGraphicsItem.ItemIsMovable)
        rect_item.setCursor(QCursor(Qt.ClosedHandCursor))
    else:
        rect_item.setFlags(QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable)
        rect_item.setCursor(QCursor(Qt.ArrowCursor))

def mouseMoveEvent(event):
    if rect_item.flags() & QGraphicsItem.ItemIsMovable:
        rect_item.setCursor(QCursor(Qt.ClosedHandCursor))
        rect = QRectF(event.scenePos(), rect_item.rect().size())
        if rect.intersects(pixmap_item.boundingRect()):
            rect_item.setRect(rect)

最后，添加一个按钮，当用户点击该按钮时，将裁剪后的图片保存到本地：

def save_image():
    rect = rect_item.rect()
    cropped_pixmap = pixmap.copy(rect.toRect())
    cropped_pixmap.save("cropped_image.png", "PNG")

button = QPushButton("Save Image")
button.clicked.connect(save_image)

完整代码如下所示：

from PyQt5.QtWidgets import QApplication, QGraphicsScene, QGraphicsView, QGraphicsPixmapItem, QFileDialog, QGraphicsRectItem, QGraphicsItem, QPushButton
from PyQt5.QtGui import QPixmap, QCursor
from PyQt5.QtCore import Qt, QRectF

app = QApplication([])
scene = QGraphicsScene()
view = QGraphicsView(scene)

filename, _ = QFileDialog.getOpenFileName(None, "Open Image", "", "Image Files (*.png *.jpg *.bmp)")
if filename:
    pixmap = QPixmap(filename)
    pixmap_item = QGraphicsPixmapItem(pixmap)
    scene.addItem(pixmap_item)
    rect_item = QGraphicsRectItem()
    rect_item.setPen(Qt.red)
    rect_item.setFlags(QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable)
    rect_item.setZValue(1)
    scene.addItem(rect_item)

def mousePressEvent(event):
    if event.button() == Qt.LeftButton:
        rect_item.setFlags(QGraphicsItem.ItemIsMovable)
        rect_item.setCursor(QCursor(Qt.ClosedHandCursor))
    else:
        rect_item.setFlags(QGraphicsItem.ItemIsMovable | QGraphicsItem.ItemIsSelectable)
        rect_item.setCursor(QCursor(Qt.ArrowCursor))

def mouseMoveEvent(event):
    if rect_item.flags() & QGraphicsItem.ItemIsMovable:
        rect_item.setCursor(QCursor(Qt.ClosedHandCursor))
        rect = QRectF(event.scenePos(), rect_item.rect().size())
        if rect.intersects(pixmap_item.boundingRect()):
            rect_item.setRect(rect)

view.mousePressEvent = mousePressEvent
view.mouseMoveEvent = mouseMoveEvent

def save_image():
    rect = rect_item.rect()
    cropped_pixmap = pixmap.copy(rect.toRect())
    cropped_pixmap.save("cropped_image.png", "PNG")

button = QPushButton("Save Image")
button.clicked.connect(save_image)

view.show()
button.show()
app.exec_()