Qt 使用opengl绘制最简单方式

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该博客介绍了如何利用libyuv库将YUV数据转换为RGB，然后使用OpenGL在Qt环境中进行渲染。首先，通过libyuv的I420ToARGB函数将YUV数据转换为RGB，接着使用ARGBScale进行缩放处理。随后，将处理后的RGB数据转换为QImage，并在继承自QGraphicsView的窗体中设置为背景。整个过程简洁高效，适用于视频帧的实时渲染。

qt使用opengl绘制yuv网上得例子有很多，使用opengl函数进行绘制。这里介绍一个更加简单得方式。

方法：

1.使用libyuv库将yuv数据转化为RGB数据

    libyuv::I420ToARGB((uint8_t*)Y_data_dest, dest_stride_Y,
        (uint8_t*)U_data_dest, dest_stride_U,
        (uint8_t*)V_data_dest, dest_stride_V,
        _rgbBuffer, _imageWidth * 4,
        _imageWidth, _imageHeight);

2.使用libyuv将转化好的RGB数据裁剪或者缩放到目标窗口大小

    libyuv::ARGBScale(_rgbBuffer, _imageWidth * 4, _imageWidth, _imageHeight, _rgbScaleBuffer,
                      scale_width*4, scale_width,
                      sacle_height, libyuv::kFilterBilinear);

3.将RGB数据转化为QImage

QImage image((uchar*)_mirror_rgbBuffer, scale_width, sacle_height, QImage::Format_ARGB32);

4.创建一个窗体继承QGraphicsView并设置显示窗口为QOpenGLWidget

  QOpenGLWidget *glWidget = new QOpenGLWidget(this);
    auto format = glWidget->format();
    format.setDepthBufferSize(0);
    format.setStencilBufferSize(0);
    format.setSamples(4);
    glWidget->setFormat(format);
    setViewport(glWidget);
    this->setScene(new QGraphicsScene);

5.将步骤4得QImage 作为QGraphicsView得背景设置进去

setBackgroundBrush(QBrush(image));

完毕

最后附上代码，代码未整理只是实现了功能

#ifndef VIDEORENDERGRAPHISVIEW_H
#define VIDEORENDERGRAPHISVIEW_H

#include <QGraphicsView>
#include <QPainter>
#include <QImage>
#include <QByteArray>
#include <QResizeEvent>
#include <QPaintEvent>
#include <QRect>
#include "VideoRender.h"

class QGraphicsScene;

class VideoRenderGraphicsView : public QGraphicsView, public VideoRender
{
public:
    explicit VideoRenderGraphicsView (QWidget *parent = Q_NULLPTR);
    ~VideoRenderGraphicsView () override;

    VideoRenderType type() override;
    QWidget *widget() override;

    void setYUV420pParameters(int width, int height, int* strides = Q_NULLPTR, int trueWidth = -1) override;
    void setFrameData(const QByteArray& data) override;
    void setFrameData(const QSharedPointer<QByteArray>& data) override;

protected:
    void resizeEvent(QResizeEvent* event) override;

private:
    uint8_t*  _rgbScaleBuffer{nullptr};
    uint8_t*  _rgbBuffer{nullptr};
    uint8_t*  _mirror_rgbBuffer{nullptr};
    int _imageWidth{0};
    int _imageHeight{0};
    int _scale_data_length{0};
    int _data_length{0};
};

#endif // VIDEORENDERGDI_H

源文件：

#include <QToolButton>
#include <QPainter>
#include "VideoRenderGraphicsView.h"
#include "HandlerClass.h"
#include "RemixLog.h"
#include "AppSession.h"
//#include "meiyan/beautyfilter.h"
#include "remixhelp.h"
#include "libyuv.h"
#include "AppEnv.h"
#include <QGraphicsView>
#include <QOpenGLWidget>
#include <QGraphicsScene>

#ifdef Q_OS_WIN
#define FONT_STR "Microsoft YaHei"
#elif defined(Q_OS_MAC)
#define FONT_STR "PingFang SC"
#endif

using namespace libyuv;

VideoRenderGraphicsView::VideoRenderGraphicsView(QWidget *parent)
    : QGraphicsView(parent), VideoRender(),
    _rgbBuffer(Q_NULLPTR), _mirror_rgbBuffer(Q_NULLPTR),
    _imageWidth(0), _imageHeight(0), _data_length(-1)
{
    setMouseTracking(true);

    QOpenGLWidget *glWidget = new QOpenGLWidget(this);
    auto format = glWidget->format();
    format.setDepthBufferSize(0);
    format.setStencilBufferSize(0);
    format.setSamples(4);
    glWidget->setFormat(format);
    setViewport(glWidget);
    this->setScene(new QGraphicsScene);
}

VideoRenderGraphicsView::~VideoRenderGraphicsView()
{
    if (_rgbBuffer != nullptr)
    {
        delete[] _rgbBuffer;
        _rgbBuffer = nullptr;
    }
    if (_mirror_rgbBuffer != nullptr)
    {
        delete[] _mirror_rgbBuffer;
        _mirror_rgbBuffer = nullptr;
    }
}

VideoRenderType VideoRenderGraphicsView::type()
{
    return VideoRenderType::OpenGl;
}

QWidget* VideoRenderGraphicsView::widget()
{
    return this;
}

void VideoRenderGraphicsView::setYUV420pParameters(int width, int height, int *strides, int trueWidth)
{
    _imageWidth = width;
    _imageHeight = height;
}

void VideoRenderGraphicsView::setFrameData(const QByteArray& data)
{
    int data_length = _imageWidth * _imageHeight * 4;

    if (data_length == 0)
    {
        return;
    }

    if (_data_length != data_length)
    {
        _data_length = data_length;
        if (_rgbBuffer)
        {
            delete [] _rgbBuffer;
            _rgbBuffer = Q_NULLPTR;
        }
        if (_mirror_rgbBuffer)
        {
            delete [] _mirror_rgbBuffer;
            _mirror_rgbBuffer = Q_NULLPTR;
        }
    }
    //旋转
    int dest_stride_Y = _imageWidth;
    int dest_stride_U = _imageWidth / 2;
    int dest_stride_V = _imageWidth / 2;

    const char  *Y_data_dest = data.constData();
    const char  *U_data_dest = Y_data_dest + _imageWidth * _imageHeight;
    const char  *V_data_dest = U_data_dest + _imageWidth * _imageHeight / 4;

    if (_rgbBuffer == Q_NULLPTR)
    {
        _rgbBuffer = new uint8_t [_data_length];
    }

    //转ARGB
    libyuv::I420ToARGB((uint8_t*)Y_data_dest, dest_stride_Y,
        (uint8_t*)U_data_dest, dest_stride_U,
        (uint8_t*)V_data_dest, dest_stride_V,
        _rgbBuffer, _imageWidth * 4,
        _imageWidth, _imageHeight);
    /*}*/
    //缩放
    int scale_data_length = this->width()*this->height()*4;
    int scale_width = this->width();
    int sacle_height = this->height();
    if (_rgbScaleBuffer == Q_NULLPTR || _scale_data_length != scale_data_length)
    {
        delete [] _rgbScaleBuffer;
        _rgbScaleBuffer = new uint8_t [scale_data_length];
    }
    libyuv::ARGBScale(_rgbBuffer, _imageWidth * 4, _imageWidth, _imageHeight, _rgbScaleBuffer,
                      scale_width*4, scale_width,
                      sacle_height, libyuv::kFilterBilinear);

    if (!m_bMirror)
    {
        if (_mirror_rgbBuffer == Q_NULLPTR || _scale_data_length != scale_data_length)
        {
            delete [] _mirror_rgbBuffer;
            _mirror_rgbBuffer = new uint8_t [scale_data_length];
        }
        libyuv::ARGBMirror(_rgbScaleBuffer, scale_width*4, _mirror_rgbBuffer, scale_width*4, scale_width, sacle_height);
    }
     _scale_data_length = scale_data_length;
    if (!m_bMirror)
    {
        QImage image((uchar*)_mirror_rgbBuffer, scale_width, sacle_height, QImage::Format_ARGB32);
         setBackgroundBrush(QBrush(image));
    }
    else
    {
        QImage image((uchar*)_rgbScaleBuffer, scale_width, sacle_height, QImage::Format_ARGB32);
        setBackgroundBrush(QBrush(image));
    }
}

void VideoRenderGraphicsView::setFrameData(const QSharedPointer<QByteArray>& data)
{
    setFrameData(*data.data());
}

void VideoRenderGraphicsView::resizeEvent(QResizeEvent *event)
{
    setSceneRect(dpiWidth(2), dpiHeight(2), width()-dpiWidth(2)*2, height()-dpiHeight(2)*2);
}