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1. WebGL 介绍
WebGL （全写 Web Graphics Library ）是一种 3D 绘图协议，这种绘图技术标准允许把 JavaScript 和 OpenGL ES 2.0 结合在一起，通过增加 OpenGL ES 2.0 的一个 JavaScript 绑定。
2. WebGL 、OpenGL 、OpenGL ES 三者的关系
3. WebGL 基础介绍
const webgl = document.getElementById("webGl-layer").getContext("webgl");
4. 基本原理
- 首先使用 webgl 纹理绘制图片
这里如果参照 https://webglfundamentals.org/webgl/lessons/zh_cn/webgl-cors-permission.html
- 绘制过程中使用片段做着色器对其 rgb 值进行修改
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
//内阴影
// 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>
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