之前分享了如何用QtPy和Dynamsoft Barcode Reader创建一个简单的桌面应用， 通过加载一张图片来识别条形码。这篇文章要分享如何加上摄像头的支持做实时扫码。

如何用Python和PyQt代码显示Camera视频流

要获取视频流，最简单的方法就是用OpenCV：

pip install opencv-python
用OpenCV来显示视频流的代码很简单，只需要一个无限循环：

import cv2
vc = cv2.VideoCapture(0)
while True:
rval, frame = vc.read()
cv2.imshow("Camera View", frame)
现在要解决的问题就是把OpenCV获取的视频帧数据通过Qt的Widget显示出来。在Qt中，不能使用循环，要用timer：

def init(self):

Create a timer.

    self.timer = QTimer()
    self.timer.timeout.connect(self.nextFrameSlot)

def nextFrameSlot(self):
rval, frame = self.vc.read()
frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
image = QImage(frame, frame.shape[1], frame.shape[0], QImage.Format_RGB888)
pixmap = QPixmap.fromImage(image)
self.label.setPixmap(pixmap)

    results = dbr.decodeBuffer(frame, 0x3FF | 0x2000000 | 0x4000000 | 0x8000000 | 0x10000000)
    out = ‘‘
    index = 0
    for result in results:
        out += "Index: " + str(index) + "\n"
        out += "Barcode format: " + result[0] + ‘\n‘
        out += "Barcode value: " + result[1] + ‘\n‘
        out += ‘-----------------------------------\n‘
        index += 1

    self.results.setText(out)

这里注意下要把颜色空间从BGR转成RGB再放到QImage中。

创建一个QHBoxLayout来放置两个button：

button_layout = QHBoxLayout()

btnCamera = QPushButton("Open camera")
btnCamera.clicked.connect(self.openCamera)
button_layout.addWidget(btnCamera)

btnCamera = QPushButton("Stop camera")
btnCamera.clicked.connect(self.stopCamera)
button_layout.addWidget(btnCamera)

layout.addLayout(button_layout)
点击button之后触发和停止timer：

def openCamera(self):
self.vc = cv2.VideoCapture(0)

vc.set(5, 30) #set FPS

    self.vc.set(3, 640) #set width
    self.vc.set(4, 480) #set height

    if not self.vc.isOpened():
        msgBox = QMessageBox()
        msgBox.setText("Failed to open camera.")
        msgBox.exec_()
        return

    self.timer.start(1000./24)

def stopCamera(self):
self.timer.stop()
监听关闭事件：

def closeEvent(self, event):

    msg = "Close the app?"
    reply = QMessageBox.question(self, ‘Message‘,
                    msg, QMessageBox.Yes, QMessageBox.No)

    if reply == QMessageBox.Yes:
        event.accept()
        self.stopCamera()
    else:
        event.ignore()

最后运行效果：

原文地址：http://blog.51cto.com/14009535/2348452