在QML插件的QGLWidget上渲染QImage [英] Rendering QImage on QGLWidget of QML plugin
问题描述
我想写一个从视频中读取帧的 QML插件（使用自定义小部件执行该任务，而不是QtMultimedia / Phonon），每个帧都转换为 QImage RGB888，然后显示在 QGLWidget （出于性能原因）。
I'm trying to write a QML plugin that reads frames from a video (using a custom widget to do that task, NOT QtMultimedia/Phonon), and each frame is converted to a QImage RGB888, and then displayed on a QGLWidget (for performance reasons). Right now nothing is draw to the screen and the screen stays white all the time.
很重要的一点是我已经有了所有这些工作没有 QGLWidget ，所以我知道问题是在QGLWidget上设置和绘制。
It's important to state that I already have all of this working without QGLWidget, so I know the issue is setting up and drawing on QGLWidget.
插件正在注册：
qmlRegisterType<Video>(uri,1,0,"Video");
因此视频插入。在它的构造函数上，我们有：
so Video is the main class of the plugin. On it's constructor we have:
Video::Video(QDeclarativeItem* parent)
: QDeclarativeItem(parent), d_ptr(new VideoPrivate(this))
{
setFlag(QGraphicsItem::ItemHasNoContents, false);
Q_D(Video);
QDeclarativeView* view = new QDeclarativeView;
view->setViewport(&d->canvas()); // canvas() returns a reference to my custom OpenGL Widget
}
到 canvas 对象，让我说我重载了 Video :: paint（），所以它调用 canvas.paint（），同时通过 QImage 作为参数，我不知道这是否是正确的方法，像这样的一些建议：
Before I jump to the canvas object, let me say that I overloaded Video::paint() so it calls canvas.paint() while passing QImage as parameter, I don't know if this is the right way to do it so I would like some advice on this:
void Video::paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QWidget* widget)
{
Q_UNUSED(painter);
Q_UNUSED(widget);
Q_UNUSED(option);
Q_D(Video);
// I know for sure at this point "d->image()" is valid, but I'm hiding the code for clarity
d->canvas().paint(painter, option, d->image());
}
canvas 被声明为 GLWidget canvas; ，并且此类的标题定义为：
The canvas object is declared as GLWidget canvas; and the header of this class is defined as:
class GLWidget : public QGLWidget
{
Q_OBJECT
public:
explicit GLWidget(QWidget* parent = NULL);
~GLWidget();
void paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QImage* image);
};
看起来很简单。现在， QGLWidget 的实现如下：
Seems pretty simple. Now, the implementation of QGLWidget is the following:
GLWidget::GLWidget(QWidget* parent)
: QGLWidget(QGLFormat(QGL::SampleBuffers), parent)
{
// Should I do something here?
// Maybe setAutoFillBackground(false); ???
}
GLWidget::~GLWidget()
{
}
最后：
void GLWidget::paint(QPainter* painter, const QStyleOptionGraphicsItem* option, QImage* image)
{
// I ignore painter because it comes from Video, so I create a new one:
QPainter gl_painter(this);
// Perform drawing as Qt::KeepAspectRatio
gl_painter.fillRect(QRectF(QPoint(0, 0), QSize(this->width(), this->height())), Qt::black);
QImage scaled_img = image->scaled(QSize(this->width(), this->height()), _ar, Qt::FastTransformation);
gl_painter.drawImage(qRound(this->width()/2) - qRound(scaled_img.size().width()/2),
qRound(this->height()/2) - qRound(scaled_img.size().height()/2),
scaled_img);
}
我缺少什么？
我最初问问 Qt论坛上的这个问题，但没有回复。
I originally asked this question on Qt Forum but got no replies.
推荐答案
已解决。问题是，我试图在我的插件中创建一个新的GL上下文，当我应该从加载它的应用程序检索GL上下文。
Solved. The problem was that I was trying to create a new GL context within my plugin when I should be retrieving the GL context from the application that loaded it.
a href =https://gitorious.org/peregrine/peregrine/blobs/master/qml-plugin/videooutput/qmlvideo.cpp =nofollow>此代码非常实用到理解如何完成。
This code was very helpful to understand how to accomplish that.
顺便说一句，我发现这些东西正在绘制 view 。这只是我需要执行 view-> show（），但是创建了另一个窗口，这不是我正在寻找。我在上面分享的链接有答案。
By the way, I discovered that the stuff was being draw inside view. It's just that I needed to execute view->show(), but that created another window which was not what I was looking for. The link I shared above has the answer.
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