给图形赋予颜色时，采用纹理贴图的方式。
每个顶点关联一个纹理坐标(Texture Coordinate),然后在图形的其他片段上进行片段插值(Fragment Interpolation)
顶点坐标如下：
float vertices[] = {
// positions // colors // texture coords
0.2f, 0.2f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, // top right
0.2f, -0.2f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, // bottom right
-0.2f, -0.2f, 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, // bottom left
-0.2f, 0.2f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f // top left
};
unsigned int indices[] = { // note that we start from 0!
0, 1, 3, // first triangle
1, 2, 3 // second triangle
};
initializeGL()函数代码：

	initializeOpenGLFunctions();
    //创建VBO和VAO对象，并赋予ID
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);
    //绑定VBO和VAO对象
    glBindVertexArray(VAO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    //为当前绑定到target的缓冲区对象创建一个新的数据存储。
    //如果data不是NULL，则使用来自此指针的数据初始化数据存储
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    //告知显卡如何解析缓冲里的属性值
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)0);
    //开启VAO管理的第一个属性值
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(3 * sizeof(float)));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void*)(6 * sizeof(float)));
    glEnableVertexAttribArray(2);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    bool success;
    shaderProgram.addShaderFromSourceFile(QOpenGLShader::Vertex, "shaders/shapes.vert");
    shaderProgram.addShaderFromSourceFile(QOpenGLShader::Fragment, "shaders/shapes.frag");
    success = shaderProgram.link();
    if (!success)
        qDebug() << "ERR:" << shaderProgram.log();
    // glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    glGenBuffers(1, &EBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
    textureWall = new QOpenGLTexture(QImage("images/wall.jpg").mirrored());
    shaderProgram.bind();
    shaderProgram.setUniformValue("textureWall", 0);
    glBindVertexArray(0);

paintGL()函数：

	glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
    shaderProgram.bind();
    glBindVertexArray(VAO);
    textureWall->bind(0);
    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, NULL);