这里是主域代码

var initShaders = function (gl, vshader, fshader) {
    var program = createProgram(gl, vshader, fshader);
    if (!program) {
        console.log('无法创建程序对象');
        return false;
    }

    gl.useProgram(program);
    gl.program = program;

    return true;
};


var createProgram = function (gl, vshader, fshader) {
    // 创建着色器对象
    var vertexShader = loadShader(gl, gl.VERTEX_SHADER, vshader);
    var fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fshader);
    if (!vertexShader || !fragmentShader) {
        return null;
    }

    // 创建程序对象
    var program = gl.createProgram();
    if (!program) {
        return null;
    }

    // 为程序对象分配顶点着色器和片元着色器
    gl.attachShader(program, vertexShader);
    gl.attachShader(program, fragmentShader);

    // 连接着色器
    gl.linkProgram(program);

    // 检查连接
    var linked = gl.getProgramParameter(program, gl.LINK_STATUS);
    if (!linked) {
        var error = gl.getProgramInfoLog(program);
        console.log('无法连接程序对象: ' + error);
        gl.deleteProgram(program);
        gl.deleteShader(fragmentShader);
        gl.deleteShader(vertexShader);
        return null;
    }
    return program;
};

var loadShader = function (gl, type, source) {
    // 创建着色器对象
    var shader = gl.createShader(type);
    if (shader == null) {
        console.log('无法创建着色器');
        return null;
    }

    // 设置着色器源代码
    gl.shaderSource(shader, source);
    // 编译着色器
    gl.compileShader(shader);

    // 检查着色器的编译状态
    var compiled = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
    if (!compiled) {
        var error = gl.getShaderInfoLog(shader);
        console.log('Failed to compile shader: ' + error);
        gl.deleteShader(shader);
        return null;
    }

    return shader;
};


var VSHADER_SOURCE = `
    attribute vec4 a_Position;
    attribute vec2 a_TexCoord;
 &