本文主要是介绍webGL编程指南 第五章 TexturedQuad_Clamp_Mirror，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
我会持续更新关于wegl的编程指南中的代码。
当前的代码不会使用书中的缩写，每一步都是会展开写。希望能给后来学习的一些帮助
git代码地址 ：空
上一章节中我们学习了如何使用varyting变量绘制图片，本章节，我们学习texParameteri的使用
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<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport"><title>Document</title><style>#canvas {width: 100vw;height: 100vw;border: 1px solid greenyellow;}</style>
</head><body>!!!!!需要指出的是要选择当前文件夹下的sky.jpg!!!!!!<!-- <input type="file" accept="image/*" onchange="loadFile(event)"> --><input type="file" onchange="loadFile(event)"><canvas id="canvas"></canvas><script>// let imgSrc = 'https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=3740843900,2506868884&fm=15&gp=0.jpg.'let vexterSource = `precision mediump float;attribute vec4 a_Position;attribute vec2 a_TexCoord;varying vec2 v_TexCoord;void main(){gl_Position = a_Position;//顶点坐标v_TexCoord = a_TexCoord;//纹理坐标系下的坐标}`let fragmentSource = `precision mediump float;uniform sampler2D u_Sampler;//纹理varying vec2 v_TexCoord;//纹理坐标系下的坐标void main(){gl_FragColor = texture2D(u_Sampler,v_TexCoord);}`let canvas = document.getElementById('canvas');let gl = canvas.getContext('webgl');//创建顶点着色器let vertextShader = gl.createShader(gl.VERTEX_SHADER);//给顶点着色器赋值gl.shaderSource(vertextShader, vexterSource);//编译顶点着色器gl.compileShader(vertextShader);//创建片元着色器let fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);//给片元着色器赋值gl.shaderSource(fragmentShader, fragmentSource)//编译片元着色器gl.compileShader(fragmentShader)//检测着色器创建是否正确if (!gl.getShaderParameter(fragmentShader, gl.COMPILE_STATUS)) {alert(gl.getShaderInfoLog(fragmentShader));}//创建程序let program = gl.createProgram();//给程序赋值gl.attachShader(program, vertextShader); gl.attachShader(program, fragmentShader);//连接程序gl.linkProgram(program);//使用此着色器gl.useProgram(program);//变量的处理//获取顶点着色器中的变量a_Positionlet a_Position = gl.getAttribLocation(program, 'a_Position');//获取顶点着色器中的变量a_TexCoordlet a_TexCoord = gl.getAttribLocation(program, 'a_TexCoord');//获取片元着色器中的变量u_Samplerlet u_Sampler = gl.getUniformLocation(program, 'u_Sampler');//顶点坐标与纹理坐标let vertexTexCoords = new Float32Array([ -0.5,0.5,-0.3,1.7,-0.5,-0.5,-0.3,-0.2,0.5,0.5,1.7,1.7,0.5,-0.5,1.7,-0.2])let f32Seize = vertexTexCoords.BYTES_PER_ELEMENT;//给定点设置坐标 几何图形与纹理的坐标let vertexBuffer = gl.createBuffer();//绑定buffergl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);//绑定数据gl.bufferData(gl.ARRAY_BUFFER, vertexTexCoords, gl.STATIC_DRAW);//给a_Position赋值gl.vertexAttribPointer(a_Position, 2, gl.FLOAT, false, f32Seize * 4, 0);//使用此变量gl.enableVertexAttribArray(a_Position);//纹理坐标let texCoordBuffer = gl.createBuffer();//绑定buffergl.bindBuffer(gl.ARRAY_BUFFER, texCoordBuffer);//绑定数据gl.bufferData(gl.ARRAY_BUFFER, vertexTexCoords, gl.STATIC_DRAW);//给a_TexCoord赋值gl.vertexAttribPointer(a_TexCoord, 2, gl.FLOAT, false, f32Seize * 4, f32Seize * 2);//使用此变量gl.enableVertexAttribArray(a_TexCoord);gl.clearColor(0, 0, 0, 1.0);//获取图片的素材 const loadFile = (event) => {var file = event.target.files[0];var reader = new FileReader();reader.onload = function (event) {// 文件里的文本会在这里被打印出来 let img = new Image();img.src = event.target.result;img.onload = () => {let texture = gl.createTexture(); showImage(texture,img)}};reader.readAsDataURL(file);};function showImage(texture, img) { document.body.appendChild(img)gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, 1);//开始0号纹理通道gl.activeTexture(gl.TEXTURE0);//想目标绑定纹理对象gl.bindTexture(gl.TEXTURE_2D, texture);//配置纹理的参数gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.MIRRORED_REPEAT);//设置着色器参数gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, img);//设置纹理数据gl.uniform1i(u_Sampler, 0) gl.clear(gl.COLOR_BUFFER_BIT);gl.drawArrays(gl.TRIANGLE_STRIP, 0, 4)}</script>
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