我正在使用 OpenCV 進行一些影像處理，并希望使用 PyQt 小部件在我的螢屏上創建一個透明的疊加層。下面我有一個基本示例，通過信號/插槽將基本幀從 opencv 發送到 PyQt 并將其顯示在視窗上。問題是我無法使用此方法獲得透明背景，而只是黑色背景：
from PyQt5 import QtGui, QtCore
from PyQt5.QtWidgets import QWidget, QApplication, QLabel, QVBoxLayout
from PyQt5.QtGui import QPixmap
import sys
import cv2
from PyQt5.QtCore import pyqtSignal, pyqtSlot, Qt, QThread
import numpy as np
import os
class VideoThread(QThread):
change_pixmap_signal = pyqtSignal(np.ndarray)
def run(self):
img = np.zeros((500, 500, 4), dtype=np.uint8)
cv2.rectangle(img, (0, 0), (200, 200), (0, 0, 255), 2)
while True
self.change_pixmap_signal.emit(img)
class App(QWidget):
def __init__(self):
super().__init__()
self.setWindowTitle("Qt live label demo")
self.disply_width = 1920
self.display_height = 1080
# create the label that holds the image
self.image_label = QLabel(self)
self.image_label.resize(self.disply_width, self.display_height)
# create a text label
self.textLabel = QLabel('Webcam')
self.setWindowFlags(QtCore.Qt.FramelessWindowHint)
self.setAttribute(QtCore.Qt.WA_TranslucentBackground)
self.setStyleSheet("background-color:transparent;")
# create a vertical box layout and add the two labels
vbox = QVBoxLayout()
vbox.addWidget(self.image_label)
vbox.addWidget(self.textLabel)
# set the vbox layout as the widgets layout
self.setLayout(vbox)
# create the video capture thread
self.thread = VideoThread()
# connect its signal to the update_image slot
self.thread.change_pixmap_signal.connect(self.update_image)
# start the thread
self.thread.start()
@pyqtSlot(np.ndarray)
def update_image(self, cv_img):
"""Updates the image_label with a new opencv image"""
qt_img = self.convert_cv_qt(cv_img)
self.image_label.setPixmap(qt_img)
def convert_cv_qt(self, cv_img):
"""Convert from an opencv image to QPixmap"""
rgb_image = cv2.cvtColor(cv_img, cv2.COLOR_BGR2RGB)
h, w, ch = rgb_image.shape
bytes_per_line = ch * w
convert_to_Qt_format = QtGui.QImage(
rgb_image.data, w, h, bytes_per_line, QtGui.QImage.Format_RGB888)
p = convert_to_Qt_format.scaled(
self.disply_width, self.display_height, Qt.KeepAspectRatio)
return QPixmap.fromImage(p)
if __name__ == "__main__":
app = QApplication(sys.argv)
a = App()
a.show()
sys.exit(app.exec_())
如果無法將帶有 alpha 通道的幀發送到 PyQt，我想知道是否可以只發送矩形 4 點位置并使用 PyQt 繪制在螢屏上繪制矩形？我認為這需要一個 widget.update() 但我不確定在哪里呼叫它。
uj5u.com熱心網友回復：
如果您打算使用透明膠片，那么顏色和影像必須是 4 通道，在您的情況下，您將 3 通道顏色傳遞給 cv2.rectangle 方法，然后在 QImage 中使用 3 通道格式進行轉換。另一方面 cv2.rectangle 回傳繪制的影像，它不會修改輸入陣列。
def run(self):
img = np.zeros((500, 500, 4), dtype=np.uint8)
output = cv2.rectangle(img, (0, 0), (200, 200), (0, 0, 255, 255), 2)
while True:
self.change_pixmap_signal.emit(output)
QThread.msleep(1)
def convert_cv_qt(self, cv_img):
h, w, ch = cv_img.shape
bytes_per_line = ch * w
convert_to_Qt_format = QtGui.QImage(
cv_img.data, w, h, bytes_per_line, QtGui.QImage.Format_RGBA8888
)
p = convert_to_Qt_format.scaled(
self.disply_width, self.display_height, Qt.KeepAspectRatio
)
return QPixmap.fromImage(p)
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