前一段时间为了适应原来应用程序迁移到4K屏下性能不足的问题， 开始研究opengl。 我用的是qt做开发的，期间在网上搜索QOpengGLWidget显示图片并且进行缩放、旋转、平移的资料， 老实说没有准确搜到， 好不容易有一篇还是要付费的。在阅读了N个网页，甚至付费下载了N个资源后， 终于自己实现了这些功能， 决定分享出来以便于后来者。 废话不多说， 以下是主要代码:

#ifndef OPENGLWIDGET_H

#define OPENGLWIDGET_H

#include <QOpenGLWidget>

#include <QOpenGLShaderProgram>

#include <QOpenGLTexture>

#include <QOpenGLFunctions>

class OpenGLWidget : public QOpenGLWidget, protected QOpenGLFunctions

{

    Q_OBJECT

public:

    OpenGLWidget(QWidget *parent = 0);

    void wheelEvent(QWheelEvent* e);

    void mousePressEvent(QMouseEvent* e);

    void mouseMoveEvent(QMouseEvent* e);

    void mouseReleaseEvent(QMouseEvent* e);

public slots:

    void initializeGL() Q_DECL_OVERRIDE;

    void resizeGL(int w, int h) Q_DECL_OVERRIDE;

    void paintGL() Q_DECL_OVERRIDE;

    void setImage(const QImage &image);

    void initTextures();

    void initShaders();

    void rotate();

private:

    QVector<QVector3D> vertices;

    QVector<QVector2D> texCoords;

    QOpenGLShaderProgram program;

    QOpenGLTexture *texture;

    QMatrix4x4 projection;

    float ratio = 1.0;

    bool m_down = false;

    QPoint m_pt;

    float m_xoff;

    float m_yoff;

    float m_angle = 0.0f;

};

#endif // OPENGLWIDGET_H

#include "openglwidget.h"

#include <QWheelEvent>

OpenGLWidget::OpenGLWidget(QWidget *parent) : QOpenGLWidget(parent)

{

}

void OpenGLWidget::initTextures()

{

    QImage image(":/images/scene.jpg");

    // 加载 Avengers.jpg 图片

    texture = new QOpenGLTexture(image);

    texture->setMinificationFilter(QOpenGLTexture::LinearMipMapLinear);

    texture->setMagnificationFilter(QOpenGLTexture::Linear);

    //重复使用纹理坐标

    //纹理坐标(1.1, 1.2)与(0.1, 0.2)相同

    texture->setWrapMode(QOpenGLTexture::Repeat);

    //分配储存空间

    texture->allocateStorage();

}

void OpenGLWidget::initShaders()

{

    //纹理坐标

    texCoords.append(QVector2D(0, 1)); //左上

    texCoords.append(QVector2D(1, 1)); //右上

    texCoords.append(QVector2D(0, 0)); //左下

    texCoords.append(QVector2D(1, 0)); //右下

    //顶点坐标

    vertices.append(QVector3D(-1, -1, 1));//左下

    vertices.append(QVector3D(1, -1, 1)); //右下

    vertices.append(QVector3D(-1, 1, 1)); //左上

    vertices.append(QVector3D(1, 1, 1));  //右上

    QOpenGLShader *vshader = new QOpenGLShader(QOpenGLShader::Vertex, this);

    const char *vsrc =

            "attribute vec2 vertex;\n"

            "attribute vec2 texCoord;\n"

            "varying vec2 texc;\n"

            "uniform mat4 transform;\n"

            "void main(void)\n"

            "{\n"

            "    gl_Position = transform*vec4(vertex, 0.0, 1.0);\n"

            "    texc = texCoord;\n"

            "}\n";

    vshader->compileSourceCode(vsrc);//编译顶点着色器代码

    QOpenGLShader *fshader = new QOpenGLShader(QOpenGLShader::Fragment, this);

    const char *fsrc =

            "uniform sampler2D texture;\n"

            "varying vec2 texc;\n"

            "void main(void)\n"

            "{\n"

            "    gl_FragColor = texture2D(texture,texc);\n"

            "}\n";

    fshader->compileSourceCode(fsrc); //编译纹理着色器代码

    program.addShader(vshader);//添加顶点着色器

    program.addShader(fshader);//添加纹理碎片着色器

    program.bindAttributeLocation("vertex", 0);//绑定顶点属性位置

    program.bindAttributeLocation("texCoord", 1);//绑定纹理属性位置

    // 链接着色器管道

    if (!program.link())

        close();

    // 绑定着色器管道

    if (!program.bind())

        close();

}

void OpenGLWidget::initializeGL()

{

    initializeOpenGLFunctions(); //初始化OPenGL功能函数

    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);    //设置背景为黑色

    glEnable(GL_TEXTURE_2D);     //设置纹理2D功能可用

    initTextures();              //初始化纹理设置

    initShaders();               //初始化shaders

}

void OpenGLWidget::resizeGL(int w, int h)

{

    glViewport(0, 0, w, h);

}

void OpenGLWidget::paintGL()

{

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //清除屏幕缓存和深度缓冲

    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);

    program.enableAttributeArray(0);

    program.enableAttributeArray(1);

    program.setAttributeArray(0, vertices.constData());

    program.setAttributeArray(1, texCoords.constData());

    program.setUniformValue("texture", 0); //将当前上下文中位置的统一变量设置为value

    if(texture->isCreated())

    {

        texture->bind();  //绑定纹理

    }

    QMatrix4x4 matrix;

    matrix.setToIdentity();

    matrix.translate(m_xoff, m_yoff,0.0);

    matrix.rotate(m_angle,0,0,1);

    matrix.scale(ratio);

    program.setUniformValue("transform", matrix);

    glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);//绘制纹理

}

void OpenGLWidget::setImage(const QImage &image)

{

    if(NULL != texture)

    {

        texture->release();

        texture->destroy();

        texture->create();

        texture->setData(image); //设置纹理图像

        //设置纹理细节

        texture->setLevelofDetailBias(-1);//值越小，图像越清晰

        update();

    }

}

void OpenGLWidget::wheelEvent(QWheelEvent* e)

{

    if(e->delta() > 0)

    {

        ratio *= 1.2;

    }

    else

    {

        ratio /= 1.2;

    }

    update();

}

void OpenGLWidget::mousePressEvent(QMouseEvent* e) {

    m_pt = e->pos();

    m_down = true;

}

void OpenGLWidget::mouseMoveEvent(QMouseEvent *e) {

    if(m_down)

    {

        float x = (m_pt.x() - e->x())*2.0/width();

        float y = (m_pt.y() - e->y())*2.0/height();

        m_xoff -= x;

        m_yoff += y;

        m_pt = e->pos();

    }

    update();

}

void OpenGLWidget::mouseReleaseEvent(QMouseEvent* e)

{

    m_down = false;

}

void OpenGLWidget::rotate()

{

    m_angle += 90.0;

    update();

}

效果截图如下：

代码参见资源：

https://download.csdn.net/download/u010947464/88781280