Qt / openGL 纹理无法正常工作
Qt / openGL textures not working correctly
我在使用 openGL 纹理时遇到 python3 / qt5 / openGL 的奇怪行为。
在两个单独的 windows 中打开两个 QOpenGLWidgets 会导致两个 Widget 之间的 openGL 纹理混合 - 在第一个 widget 中更改纹理会导致在第二个 widget 中更改纹理。尽管它们应该有不同的 openGL 上下文..!
提供了演示此问题的代码（见下文）- 请先尝试，然后再提出解决方案。代码简洁地演示了两种情况：
1) 创建两个共享相同 parent Widget
的 QOpenGLWidget
- 工作正常 - 没有 "texture mixing"
2) 创建两个没有 parents
的 QOpenGLWidgets
- 小部件作为单独打开 windows
- Qt/OpenGL 系统搞乱了 OpenGL 纹理：改变第一个 window 中的纹理，意外地改变了第二个 window 的纹理！
（记得调整大小/点击第二个 window 看到这个）
为了修复案例 (2)，我还尝试强制两个小部件共享相同的 OpenGLContext .. 但没有成功。
http://doc.qt.io/qt-5/qopenglwidget.html
表示如下：
Creating extra QOpenGLContext instances that share resources like textures with the QOpenGLWidget's context is also possible. 'Simply' pass the pointer returned from context() to QOpenGLContext::setShareContext() before calling QOpenGLContext::create()
是的，我可以实例化自定义 QOpenGLContext 以进行共享，但是无法强制 QOpenGLWidget 使用该自定义上下文：QOpenGLWidget 在某处（哪里？）自动实例化 QOpenGLContext ..我只能在 initializeGL 中访问它（ "self.context()")，但此时上下文的“.create()”方法已被调用..！ .. 因此无法在任何地方填充我的自定义 QOpenGLContext。
我还尝试了以下方法：我们创建了一个 class 变量
glcontext=None
在小部件的（请首先查看下面的完整示例）initializeGL 方法中，我正在尝试这样做：
if (VideoImageWidget.glcontext==None):
print("VideoImageWidget: initializeGL: creating context for sharing")
VideoImageWidget.glcontext=QtGui.QOpenGLContext()
ok=VideoImageWidget.glcontext.create()
print("VideoImageWidget: initializeGL: created context for sharing",VideoImageWidget.glcontext,ok)
context=self.context()
print("VideoImageWidget: initializeGL: automatically created context:",context)
context.setShareContext(VideoImageWidget.glcontext)
ok=context.create() # must call this ..
print("VideoImageWidget: initializeGL: recreated my context:",ok)
但这不起作用.. VideoImageWidget 不再显示任何图像。
这是一团糟！非常感谢帮助！
相关：
Is it possible to use the same OpenGL context between top-level windows in Qt?
How to share OpenGL context or data?
演示程序：
import sys
import time
from PyQt5 import QtWidgets, QtCore, QtGui # Qt5
from OpenGL.GL import *
from PIL import Image
"""
Demonstrating a bug (?) in QOpenGLWidget / Qt OpenGL insfrastructure :
You need:
* to have two tiff images ("base.tif" and "2.tif") in the same directory
* to remove/install some libraries:
sudo apt-get install python3-pyqt5 pip3
sudo apt-get remove python3-opengl # we want the most recent version of the opengl bindings
sudo pip3 install PyOpenGL PyOpenGL_accelerate
sudo pip3 install imutils
Usage:
* look for the tag "TOGGLE HERE" below to switch between nested QWidgets / individual windows
* run program with
python3 context_test.py
What's going on here?
* Press the button a few times : a new image appears to the first widget
* The image should appear only to the first widget
* .. but it appears in both widgets if we set "nested=False", i.e. when the widgets constitute individual windows
* .. confirm this by clicking / resizing the second window after clicking the button a few times
Why this happens?
* Qt creates some sort of "top-level" (?) opengl context that is referring to the same texture ids = bug ?
This code is licensed under the do-with-it-whatever-you-want license, written by Sampsa Riikonen, 2017
"""
def getImg(fname):
im =QtGui.QImage(fname)
im =im.convertToFormat(QtGui.QImage.Format_RGB888)
ix =im.width()
iy =im.height()
ptr=im.bits()
ptr.setsize(im.byteCount())
return ptr.asstring(), ix, iy
class VideoImageWidget(QtWidgets.QOpenGLWidget): # http://doc.qt.io/qt-5/qopenglwidget.html # Qt5
def __init__(self,parent=None):
super().__init__(parent=parent)
self.parent=parent
self.baseimage, self.ix, self.iy =getImg("base.tif")
self.gl_format=GL_RGB
self.ratio =1
self.picratio =1
def changeTexture(self,image,ix,iy):
glBindTexture(GL_TEXTURE_2D, self.tex) # this is the texture we will manipulate
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexImage2D(GL_TEXTURE_2D, 0, self.gl_format, ix, iy, 0, self.gl_format, GL_UNSIGNED_BYTE, image) # load bitmap to texture
self.picratio=self.iy/self.ix
def resetTexture(self):
self.changeTexture(self.baseimage,self.ix,self.iy)
def initializeGL(self):
# "This function should set up any required OpenGL resources and state"
glEnable(GL_TEXTURE_2D)
self.tex = glGenTextures(1) # create a new texture
# https://www.khronos.org/opengles/sdk/docs/man/xhtml/glGenTextures.xml
# "it is guaranteed that none of the returned names was in use immediately before the call"
print("VideoImageWidget: glGenTextures returned:",self.tex)
self.resetTexture()
def paintGL(self):
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) # Clear The Screen And The Depth Buffer
glLoadIdentity() # Reset The View
glBindTexture(GL_TEXTURE_2D, self.tex) # this is the texture we will manipulate
glBegin(GL_QUADS)
dz=0
r=self.ratio/self.picratio # screen h/w // picture h/w
if (r<1): # screen wider than image
dy=1
dx=r
elif (r>1): # screen taller than image
dx=1
dy=1/r
else:
dx=1
dy=1
glTexCoord2f(0.0, 0.0); glVertex3f(-dx, dy, dz)
glTexCoord2f(1.0, 0.0); glVertex3f( dx, dy, dz)
glTexCoord2f(1.0, 1.0); glVertex3f( dx,-dy, dz)
glTexCoord2f(0.0, 1.0); glVertex3f(-dx,-dy, dz)
glEnd()
def resizeGL(self, width, height):
"""Called upon window resizing: reinitialize the viewport.
"""
glViewport(0, 0, width, height)
glLoadIdentity()
glOrtho(-1, 1, 1, -1, -1, 1)
self.ratio=height/width
@QtCore.pyqtSlot(object)
def frameReceived(self,frame):
buf =frame[0]
width =frame[1]
height=frame[2]
print("VideoImageWidget updating with frame",width,height)
self.changeTexture(buf,width,height)
self.update()
class MyGui(QtWidgets.QMainWindow):
f1 = QtCore.pyqtSignal(object)
f2 = QtCore.pyqtSignal(object)
def __init__(self,parent=None):
super().__init__(parent)
self.cw=QtWidgets.QWidget(self)
self.setCentralWidget(self.cw)
self.lay = QtWidgets.QVBoxLayout(self.cw)
self.b = QtWidgets.QPushButton("Send frame",self.cw)
# *** TOGGLE HERE ***
# nested=True # *** widgets sitting in the QMainWindow
nested=False # *** individual windows
self.lay.addWidget(self.b)
if (nested):
self.v1 = VideoImageWidget(parent=self.cw)
self.v2 = VideoImageWidget(parent=self.cw)
self.lay.addWidget(self.v1)
self.lay.addWidget(self.v2)
else:
self.v1 = VideoImageWidget(parent=None)
self.v2 = VideoImageWidget(parent=None)
self.v1.show()
self.v2.show()
self.b.clicked. connect(self.clicked)
self.f1. connect(self.v1.frameReceived)
self.newimage, self.ix, self.iy =getImg("2.tif")
@QtCore.pyqtSlot()
def clicked(self):
print("emitting frame")
self.f1.emit([self.newimage, self.ix, self.iy]) # update _only_ the first VideoImageWidget
if (__name__=="__main__"):
app=QtWidgets.QApplication([])
# *** Set this to apply context sharing ***
# app.setAttribute(QtCore.Qt.AA_ShareOpenGLContexts)
"""
.. but that does not work for textures
See the last comment on this post:
"I've realised that this does not solve the problem in the question, as it does not actually share the context, but enables sharing of a subset of resources .."
That is said also in the qt docs, but in an extremely implicit way..
http://doc.qt.io/qt-5/qopenglwidget.html
"Creating extra QOpenGLContext instances that share resources like textures .. "
"""
print("OpenGL context sharing status:",app.testAttribute(QtCore.Qt.AA_ShareOpenGLContexts))
mg=MyGui()
mg.show()
app.exec_()
我找到了修复示例的方法，但我不知道它是否是 "correct" 解决方案，因为我对 OpenGL 几乎一无所知（也许这有帮助）。
不管怎样，我所做的就是这样：
@QtCore.pyqtSlot(object)
def frameReceived(self, frame):
self.makeCurrent()
...
根据 makeCurrent 的文档：
It is not necessary to call this function in most cases, because it is
called automatically before invoking paintGL().
所以问题似乎是：这里提到的 "other cases" 是什么，它们有什么不同...
我在使用 openGL 纹理时遇到 python3 / qt5 / openGL 的奇怪行为。
在两个单独的 windows 中打开两个 QOpenGLWidgets 会导致两个 Widget 之间的 openGL 纹理混合 - 在第一个 widget 中更改纹理会导致在第二个 widget 中更改纹理。尽管它们应该有不同的 openGL 上下文..!
提供了演示此问题的代码（见下文）- 请先尝试，然后再提出解决方案。代码简洁地演示了两种情况：
1) 创建两个共享相同 parent Widget
的 QOpenGLWidget- 工作正常 - 没有 "texture mixing"
2) 创建两个没有 parents
的 QOpenGLWidgets- 小部件作为单独打开 windows
- Qt/OpenGL 系统搞乱了 OpenGL 纹理：改变第一个 window 中的纹理，意外地改变了第二个 window 的纹理！ （记得调整大小/点击第二个 window 看到这个）
为了修复案例 (2)，我还尝试强制两个小部件共享相同的 OpenGLContext .. 但没有成功。
http://doc.qt.io/qt-5/qopenglwidget.html
表示如下：
Creating extra QOpenGLContext instances that share resources like textures with the QOpenGLWidget's context is also possible. 'Simply' pass the pointer returned from context() to QOpenGLContext::setShareContext() before calling QOpenGLContext::create()
是的，我可以实例化自定义 QOpenGLContext 以进行共享，但是无法强制 QOpenGLWidget 使用该自定义上下文：QOpenGLWidget 在某处（哪里？）自动实例化 QOpenGLContext ..我只能在 initializeGL 中访问它（ "self.context()")，但此时上下文的“.create()”方法已被调用..！ .. 因此无法在任何地方填充我的自定义 QOpenGLContext。
我还尝试了以下方法：我们创建了一个 class 变量
glcontext=None
在小部件的（请首先查看下面的完整示例）initializeGL 方法中，我正在尝试这样做：
if (VideoImageWidget.glcontext==None):
print("VideoImageWidget: initializeGL: creating context for sharing")
VideoImageWidget.glcontext=QtGui.QOpenGLContext()
ok=VideoImageWidget.glcontext.create()
print("VideoImageWidget: initializeGL: created context for sharing",VideoImageWidget.glcontext,ok)
context=self.context()
print("VideoImageWidget: initializeGL: automatically created context:",context)
context.setShareContext(VideoImageWidget.glcontext)
ok=context.create() # must call this ..
print("VideoImageWidget: initializeGL: recreated my context:",ok)
但这不起作用.. VideoImageWidget 不再显示任何图像。
这是一团糟！非常感谢帮助！
相关：
Is it possible to use the same OpenGL context between top-level windows in Qt?
How to share OpenGL context or data?
演示程序：
import sys
import time
from PyQt5 import QtWidgets, QtCore, QtGui # Qt5
from OpenGL.GL import *
from PIL import Image
"""
Demonstrating a bug (?) in QOpenGLWidget / Qt OpenGL insfrastructure :
You need:
* to have two tiff images ("base.tif" and "2.tif") in the same directory
* to remove/install some libraries:
sudo apt-get install python3-pyqt5 pip3
sudo apt-get remove python3-opengl # we want the most recent version of the opengl bindings
sudo pip3 install PyOpenGL PyOpenGL_accelerate
sudo pip3 install imutils
Usage:
* look for the tag "TOGGLE HERE" below to switch between nested QWidgets / individual windows
* run program with
python3 context_test.py
What's going on here?
* Press the button a few times : a new image appears to the first widget
* The image should appear only to the first widget
* .. but it appears in both widgets if we set "nested=False", i.e. when the widgets constitute individual windows
* .. confirm this by clicking / resizing the second window after clicking the button a few times
Why this happens?
* Qt creates some sort of "top-level" (?) opengl context that is referring to the same texture ids = bug ?
This code is licensed under the do-with-it-whatever-you-want license, written by Sampsa Riikonen, 2017
"""
def getImg(fname):
im =QtGui.QImage(fname)
im =im.convertToFormat(QtGui.QImage.Format_RGB888)
ix =im.width()
iy =im.height()
ptr=im.bits()
ptr.setsize(im.byteCount())
return ptr.asstring(), ix, iy
class VideoImageWidget(QtWidgets.QOpenGLWidget): # http://doc.qt.io/qt-5/qopenglwidget.html # Qt5
def __init__(self,parent=None):
super().__init__(parent=parent)
self.parent=parent
self.baseimage, self.ix, self.iy =getImg("base.tif")
self.gl_format=GL_RGB
self.ratio =1
self.picratio =1
def changeTexture(self,image,ix,iy):
glBindTexture(GL_TEXTURE_2D, self.tex) # this is the texture we will manipulate
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR)
glTexImage2D(GL_TEXTURE_2D, 0, self.gl_format, ix, iy, 0, self.gl_format, GL_UNSIGNED_BYTE, image) # load bitmap to texture
self.picratio=self.iy/self.ix
def resetTexture(self):
self.changeTexture(self.baseimage,self.ix,self.iy)
def initializeGL(self):
# "This function should set up any required OpenGL resources and state"
glEnable(GL_TEXTURE_2D)
self.tex = glGenTextures(1) # create a new texture
# https://www.khronos.org/opengles/sdk/docs/man/xhtml/glGenTextures.xml
# "it is guaranteed that none of the returned names was in use immediately before the call"
print("VideoImageWidget: glGenTextures returned:",self.tex)
self.resetTexture()
def paintGL(self):
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) # Clear The Screen And The Depth Buffer
glLoadIdentity() # Reset The View
glBindTexture(GL_TEXTURE_2D, self.tex) # this is the texture we will manipulate
glBegin(GL_QUADS)
dz=0
r=self.ratio/self.picratio # screen h/w // picture h/w
if (r<1): # screen wider than image
dy=1
dx=r
elif (r>1): # screen taller than image
dx=1
dy=1/r
else:
dx=1
dy=1
glTexCoord2f(0.0, 0.0); glVertex3f(-dx, dy, dz)
glTexCoord2f(1.0, 0.0); glVertex3f( dx, dy, dz)
glTexCoord2f(1.0, 1.0); glVertex3f( dx,-dy, dz)
glTexCoord2f(0.0, 1.0); glVertex3f(-dx,-dy, dz)
glEnd()
def resizeGL(self, width, height):
"""Called upon window resizing: reinitialize the viewport.
"""
glViewport(0, 0, width, height)
glLoadIdentity()
glOrtho(-1, 1, 1, -1, -1, 1)
self.ratio=height/width
@QtCore.pyqtSlot(object)
def frameReceived(self,frame):
buf =frame[0]
width =frame[1]
height=frame[2]
print("VideoImageWidget updating with frame",width,height)
self.changeTexture(buf,width,height)
self.update()
class MyGui(QtWidgets.QMainWindow):
f1 = QtCore.pyqtSignal(object)
f2 = QtCore.pyqtSignal(object)
def __init__(self,parent=None):
super().__init__(parent)
self.cw=QtWidgets.QWidget(self)
self.setCentralWidget(self.cw)
self.lay = QtWidgets.QVBoxLayout(self.cw)
self.b = QtWidgets.QPushButton("Send frame",self.cw)
# *** TOGGLE HERE ***
# nested=True # *** widgets sitting in the QMainWindow
nested=False # *** individual windows
self.lay.addWidget(self.b)
if (nested):
self.v1 = VideoImageWidget(parent=self.cw)
self.v2 = VideoImageWidget(parent=self.cw)
self.lay.addWidget(self.v1)
self.lay.addWidget(self.v2)
else:
self.v1 = VideoImageWidget(parent=None)
self.v2 = VideoImageWidget(parent=None)
self.v1.show()
self.v2.show()
self.b.clicked. connect(self.clicked)
self.f1. connect(self.v1.frameReceived)
self.newimage, self.ix, self.iy =getImg("2.tif")
@QtCore.pyqtSlot()
def clicked(self):
print("emitting frame")
self.f1.emit([self.newimage, self.ix, self.iy]) # update _only_ the first VideoImageWidget
if (__name__=="__main__"):
app=QtWidgets.QApplication([])
# *** Set this to apply context sharing ***
# app.setAttribute(QtCore.Qt.AA_ShareOpenGLContexts)
"""
.. but that does not work for textures
See the last comment on this post:
"I've realised that this does not solve the problem in the question, as it does not actually share the context, but enables sharing of a subset of resources .."
That is said also in the qt docs, but in an extremely implicit way..
http://doc.qt.io/qt-5/qopenglwidget.html
"Creating extra QOpenGLContext instances that share resources like textures .. "
"""
print("OpenGL context sharing status:",app.testAttribute(QtCore.Qt.AA_ShareOpenGLContexts))
mg=MyGui()
mg.show()
app.exec_()
我找到了修复示例的方法，但我不知道它是否是 "correct" 解决方案，因为我对 OpenGL 几乎一无所知（也许这有帮助）。
不管怎样，我所做的就是这样：
@QtCore.pyqtSlot(object)
def frameReceived(self, frame):
self.makeCurrent()
...
根据 makeCurrent 的文档：
It is not necessary to call this function in most cases, because it is called automatically before invoking paintGL().
所以问题似乎是：这里提到的 "other cases" 是什么，它们有什么不同...