尝试将图像从 QThread 发送到 PyQt 中的主线程或其他线程

Question

我试图在主线程中显示来自另一个线程的图像，甚至可能是一个新线程。问题是我无法让图像显示在其他任何地方。我正在使用线程 _thread 下载图像，因此它不会冻结 gui，但我似乎无法使用 QImage 或 QPixmap 正确地将其从那里取出。
我知道如何在信号中使用字符串等，如下例所示，但我不确定如何正确发送信号中的图像。我曾尝试使用请求来获取图像 url 并将其发送到有效的主服务器，但我无法在主服务器中获取字符串，然后也只能快速下载它。由于暂时冻结了 GUI，这也不是一个好的选择。

此代码是一个示例，它表明我可以完成所有工作并在我想要但不希望的情况下在 main 中下载图像。

import urllib2
from PyQt4 import QtGui
from PyQt4.QtCore import QThread, pyqtSignal
from PyQt4.QtGui import QApplication, QPixmap
import sys

class MainWindow(QtGui.QWidget):
    def __init__(self):
        super(self.__class__, self).__init__()
        layout = QtGui.QVBoxLayout(self)
        self._Button = QtGui.QPushButton()
        self._Button.setObjectName("_Button")
        self.line_edit = QtGui.QLineEdit()
        self.line_edit.setObjectName("line_edit")
        self.txt_box = QtGui.QTextEdit()
        self.txt_box.setObjectName("txt_Box")
        self.img_label = QtGui.QLabel()
        self.img_label.setObjectName("img_label")
        layout.addWidget(self._Button)
        layout.addWidget(self.line_edit)
        layout.addWidget(self.img_label)
        layout.addWidget(self.txt_box)

        self.pixmap = QPixmap()
        self._thread = test_thread()
        self._Button.clicked.connect(self.start_thread)
        self.get_Text = self._thread.test_Signal.connect(self.line_edit.setText)

        self.urls = 'https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_120x44dp.png'
        data = urllib2.urlopen(self.urls).read()
        self.pixmap.loadFromData(data)
        self.img_label.setPixmap(self.pixmap)

    def start_thread(self):
        self._thread.start()
        self._thread.test_Signal.connect(self.txt_box.setText)


class test_thread(QThread):
    test_Signal = pyqtSignal(str)
    def __init__(self):
        super(test_thread, self).__init__()

    def run(self):
        string = 'This is a test string.'
        self.test_Signal.emit(string)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec_())

这段代码显示了我想要做的更多事情。

import urllib2
from PyQt4 import QtGui
from PyQt4.QtCore import QThread, pyqtSignal
from PyQt4.QtGui import QApplication, QPixmap
import sys

class MainWindow(QtGui.QWidget):
    def __init__(self):
        super(self.__class__, self).__init__()
        layout = QtGui.QVBoxLayout(self)
        self._Button = QtGui.QPushButton()
        self._Button.setObjectName("_Button")
        self.line_edit = QtGui.QLineEdit()
        self.line_edit.setObjectName("line_edit")
        self.txt_box = QtGui.QTextEdit()
        self.txt_box.setObjectName("txt_Box")
        self.img_label = QtGui.QLabel()
        self.img_label.setObjectName("img_label")
        layout.addWidget(self._Button)
        layout.addWidget(self.line_edit)
        layout.addWidget(self.img_label)
        layout.addWidget(self.txt_box)

        self.pixmap = QPixmap()
        self._thread = test_thread()
        self._Button.clicked.connect(self.start_thread)
        self.get_Text = self._thread.test_Signal.connect(self.line_edit.setText)

    "...Send signal here and show image. EX:"
    "...self._thread.image_Signal.connect(self.img_label.setPixmap)...."
    "...or...."
    def show_image_here(self):
        "....Send image here after downloaded in thread...."

    def start_thread(self):
        self._thread.start()
        self._thread.test_Signal.connect(self.txt_box.setText)

class test_thread(QThread):
    test_Signal = pyqtSignal(str)

    "....Example image signal...."
    "....image_Signal = pyqtSignal()...."

    def __init__(self):
        super(test_thread, self).__init__()
        self.pixmap = QPixmap()

    def run(self):
        string = 'This is a test string.'
        self.test_Signal.emit(string)

        self.urls = 'https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_120x44dp.png'
        data = urllib2.urlopen(self.urls).read()
        self.pixmap.loadFromData(data)
        "....Not sure what to do here...."

if __name__ == '__main__':
    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec_())

有人可以帮帮我吗？谢谢。

Answer 1

又看了看，我发现了这个帖子PySide threading and http downloading

我希望我能早点找到它，因为我在发布之前做了很多搜索。回复该主题的人reclosedev 也在 cmets 中发布了这个：
https://pastebin.com/b4MD5jKh
这极大地帮助我更好地理解了一些事情。我使用了他的代码并稍加修改以适应我的需求，它非常适合我想做的事情。
这是我使用原始示例的完整工作代码，供任何可能发现它有用的人使用。

import urllib2
from PyQt4 import QtGui, QtCore
from PyQt4.QtCore import QThread, pyqtSignal
from PyQt4.QtGui import QApplication
import sys

class MainWindow(QtGui.QWidget):
    def __init__(self):
        super(self.__class__, self).__init__()
        layout = QtGui.QVBoxLayout(self)
        self._Button = QtGui.QPushButton()
        self._Button.setObjectName("_Button")
        self.line_edit = QtGui.QLineEdit()
        self.line_edit.setObjectName("line_edit")
        self.txt_box = QtGui.QTextEdit()
        self.txt_box.setObjectName("txt_Box")
        self.img_label = QtGui.QLabel()
        self.img_label.setObjectName("img_label")
        self.imagepreview = ImagePreview()
        layout.addWidget(self._Button)
        layout.addWidget(self.line_edit)
        layout.addWidget(self.img_label)
        layout.addWidget(self.txt_box)
        layout.addWidget(self.imagepreview)

        self._thread = test_thread()
        self._Button.clicked.connect(self.start_thread)
        self._Button.clicked.connect(self.imagepreview.startDownload)
        self.get_Text = self._thread.test_Signal.connect(self.line_edit.setText)

    def start_thread(self):
        self._thread.start()
        self._thread.test_Signal.connect(self.txt_box.setText)


class test_thread(QThread):
    test_Signal = pyqtSignal(str)

    def __init__(self):
        super(test_thread, self).__init__()

    def run(self):
        string = 'This is a test string.'
        self.test_Signal.emit(string)


class DownloadThread(QtCore.QThread):
    data_downloaded = pyqtSignal()

    def __init__(self, url):
        QtCore.QThread.__init__(self)
        self.url = url
        self._data = None

    def run(self):
        self._data = urllib2.urlopen(self.url).read()
        self.data_downloaded.emit()

    def get_data(self):
        return self._data


class ImagePreview(QtGui.QWidget):
    def __init__(self, parent=None):
        super(ImagePreview, self).__init__(parent)
        self.setMinimumSize(50, 50)
        self.pixmap = None

    def paintEvent(self, paintEvent):
        painter = QtGui.QPainter(self)
        if (self.pixmap):
            painter.drawPixmap(0, 0, self.pixmap)

    def startDownload(self):
        self.download_thread = DownloadThread('https://www.google.com/images/branding/googlelogo/2x/googlelogo_color_120x44dp.png')
        self.download_thread.start()
        self.download_thread.data_downloaded.connect(self.ondownloadFinished)

    def ondownloadFinished(self):
        self.paintImage()
        print("download finished")

    def paintImage(self):
        print("Painting")
        pixmap = QtGui.QPixmap()
        pixmap.loadFromData(self.download_thread.get_data())
        self.setPixmap(pixmap)

    def setPixmap(self, pixmap):
        self.pixmap = pixmap
        self.setMinimumSize(pixmap.width(), pixmap.height())
        self.update()

if __name__ == '__main__':
    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec_())