1. WebGL介绍
WebGL（全写Web Graphics Library）是一种3D绘图协定，这种绘图技术标准容许把JavaScript和OpenGL ES 2.0联合在一起，通过减少OpenGL ES 2.0的一个JavaScript绑定。
2. WebGL、OpenGL、OpenGL ES 三者的关系
3. WebGL 根底介绍
const webgl = document.getElementById("webGl-layer").getContext("webgl");4. 基本原理
- 首先应用webgl 纹理绘制图片
这里如果参照 https://webglfundamentals.org...
- 绘制过程中应用片段做着色器对其 rgb 值进行批改
5. 具体实现
<!DOCTYPE html><html lang="ch"><head> <meta charset="UTF-8"> <title>VertexBuffer</title></head><body><canvas id="webGl-layer" width="532" height="300"></canvas><div> <label for="r1">饱和度:</label><input type="range" id="r1" value="0"/></div><div> <label for="r2">R:</label><input type="range" id="r2" value="0"/></div><div> <label for="r3">G:</label><input type="range" id="r3" value="0"/></div><div> <label for="r4">B:</label><input type="range" id="r4" value="0"/></div><script> const webgl = document.getElementById("webGl-layer").getContext("webgl"); const range1 = document.getElementById("r1"), range2 = document.getElementById("r2"), range3 = document.getElementById("r3"), range4 = document.getElementById("r4"); webgl.viewport(0, 0, 532, 300); const vertexShader2D = ` precision mediump float; attribute vec4 position; attribute vec4 inputTextureCoordinate; varying vec2 textureCoordinate; void main() { gl_Position = position; textureCoordinate = vec2((position.x+1.0)/2.0, 1.0-(position.y+1.0)/2.0); } `; const fragmentShader2D = ` precision mediump float; varying vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform float size; uniform float saturation; uniform float r; uniform float g; uniform float b; uniform float a; void main() { vec4 texture = texture2D(inputImageTexture, textureCoordinate); texture.r += r; // 图片整体 r 值 texture.g += g; // 图片整体 g 值 texture.b += b; // 图片整体 b 值 // texture.a = 0.5; // 图片整体 a 值 //内暗影 // float dist = distance(textureCoordinate, vec2(0.5, 0.5)); // texture.rgb *= smoothstep(0.8, size * 0.799, dist * (1.0 + size)); //饱和度 float average = (texture.r + texture.g + texture.b) / 3.0; if (saturation > 0.0) { texture.rgb += (average - texture.rgb) * (1.0 - 1.0 / (1.001 - saturation)); } else { texture.rgb += (average - texture.rgb) * (-saturation); } gl_FragColor = texture; } `; function createShader(gl, type, source) { const shader = gl.createShader(type); gl.shaderSource(shader, source); gl.compileShader(shader); if (gl.getShaderParameter(shader, gl.COMPILE_STATUS)) { return shader; } console.log(gl.getShaderInfoLog(shader)); gl.deleteShader(shader); } function createProgram(gl, vertexShader, fragmentShader) { const program = gl.createProgram(); gl.attachShader(program, vertexShader); gl.attachShader(program, fragmentShader); gl.linkProgram(program); if (gl.getProgramParameter(program, gl.LINK_STATUS)) { webgl.useProgram(program); return program; } console.error(gl.getProgramInfoLog(program)); gl.deleteProgram(program); } function createTextureByImageObject(gl, imgObject) { gl.activeTexture(gl.TEXTURE0); const textureObject = gl.createTexture(); gl.bindTexture(gl.TEXTURE_2D, textureObject); gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, imgObject); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE); gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE) return textureObject; } const vertices = [ 1.0, 1.0, 1.0, -1.0, -1.0, 1.0, -1.0, -1.0 ]; const vertexShader = createShader(webgl, webgl.VERTEX_SHADER, vertexShader2D), fragmentShader = createShader(webgl, webgl.FRAGMENT_SHADER, fragmentShader2D), program = createProgram(webgl, vertexShader, fragmentShader), buffer = webgl.createBuffer(); webgl.bindBuffer(webgl.ARRAY_BUFFER, buffer); webgl.bufferData(webgl.ARRAY_BUFFER, new Float32Array(vertices), webgl.STATIC_DRAW); let v4PositionIndex = webgl.getAttribLocation(program, "position"); webgl.enableVertexAttribArray(v4PositionIndex); webgl.vertexAttribPointer(v4PositionIndex, 2, webgl.FLOAT, false, 0, 0); let img = new Image(); img.crossOrigin = "anonymous"; img.src = "http://static.atvideo.cc/2021/01/04/09/47/1609724837(1).jpg"; img.onload = function () { document.body.append(img); createTextureByImageObject(webgl, img); let saturationUniform = webgl.getUniformLocation(program, "saturation"); let rUniform = webgl.getUniformLocation(program, "r"); let gUniform = webgl.getUniformLocation(program, "g"); let bUniform = webgl.getUniformLocation(program, "b"); // let sizeUniform = webgl.getUniformLocation(program, "size"); // webgl.uniform1f(sizeUniform, 2.0); const uniform = webgl.getUniformLocation(program, "inputImageTexture"); webgl.uniform1i(uniform, 0); webgl.drawArrays(webgl.TRIANGLE_STRIP, 0, 4); range1.addEventListener("change", function () { const val = Number(range1.value) / 100; webgl.uniform1f(saturationUniform, val); webgl.drawArrays(webgl.TRIANGLE_STRIP, 0, 4); }); range2.addEventListener("change", function () { const val = Number(range2.value) / 100; webgl.uniform1f(rUniform, val); webgl.drawArrays(webgl.TRIANGLE_STRIP, 0, 4); }); range3.addEventListener("change", function () { const val = Number(range3.value) / 100; webgl.uniform1f(gUniform, val); webgl.drawArrays(webgl.TRIANGLE_STRIP, 0, 4); }); range4.addEventListener("change", function () { const val = Number(range4.value) / 100; webgl.uniform1f(bUniform, val); webgl.drawArrays(webgl.TRIANGLE_STRIP, 0, 4); }); }</script></body></html>