WebGL 图像处理 - Part.1 WebGL 图像处理 Example4 by CWEBGL - 代码

WebGL 图像处理 - Part.1 WebGL 图像处理 Example4

2018-09-18 20:54

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</style>

<script id="2d-vertex-shader" type="x-shader/x-vertex">
attribute vec2 a_position;
attribute vec2 a_texCoord;

uniform vec2 u_resolution;

varying vec2 v_texCoord;

void main() {
   // convert the rectangle from pixels to 0.0 to 1.0
   vec2 zeroToOne = a_position / u_resolution;

// convert from 0->1 to 0->2
   vec2 zeroToTwo = zeroToOne * 2.0;

// convert from 0->2 to -1->+1 (clipspace)
   vec2 clipSpace = zeroToTwo - 1.0;

gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);

// pass the texCoord to the fragment shader
   // The GPU will interpolate this value between points.
   v_texCoord = a_texCoord;
}
</script>

<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;

// our texture
uniform sampler2D u_image;
uniform vec2 u_textureSize;
uniform float u_kernel[9];
uniform float u_kernelWeight;

// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;

void main() {
   vec2 onePixel = vec2(1.0, 1.0) / u_textureSize;
   vec4 colorSum =
       texture2D(u_image, v_texCoord + onePixel * vec2(-1, -1)) * u_kernel[0] +
       texture2D(u_image, v_texCoord + onePixel * vec2( 0, -1)) * u_kernel[1] +
       texture2D(u_image, v_texCoord + onePixel * vec2( 1, -1)) * u_kernel[2] +
       texture2D(u_image, v_texCoord + onePixel * vec2(-1,  0)) * u_kernel[3] +
       texture2D(u_image, v_texCoord + onePixel * vec2( 0,  0)) * u_kernel[4] +
       texture2D(u_image, v_texCoord + onePixel * vec2( 1,  0)) * u_kernel[5] +
       texture2D(u_image, v_texCoord + onePixel * vec2(-1,  1)) * u_kernel[6] +
       texture2D(u_image, v_texCoord + onePixel * vec2( 0,  1)) * u_kernel[7] +
       texture2D(u_image, v_texCoord + onePixel * vec2( 1,  1)) * u_kernel[8] ;

gl_FragColor = vec4((colorSum / u_kernelWeight).rgb, 1);
}
</script>

<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>

HTML代码

"use strict";

function main() {
  var image = new Image();
  image.crossOrigin = true;
  image.src = "https://webglfundamentals.org/webgl/resources/leaves.jpg";  // MUST BE SAME DOMAIN!!!
  image.onload = function() {
    render(image);
  }
}

function render(image) {
  // Get A WebGL context
  /** @type {HTMLCanvasElement} */
  var canvas = document.getElementById("canvas");
  var gl = canvas.getContext("webgl");
  if (!gl) {
    return;
  }

// setup GLSL program
  var program = webglUtils.createProgramFromScripts(gl, ["2d-vertex-shader", "2d-fragment-shader"]);

// look up where the vertex data needs to go.
  var positionLocation = gl.getAttribLocation(program, "a_position");
  var texcoordLocation = gl.getAttribLocation(program, "a_texCoord");

// Create a buffer to put three 2d clip space points in
  var positionBuffer = gl.createBuffer();
  // Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
  gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
  // Set a rectangle the same size as the image.
  setRectangle( gl, 0, 0, image.width, image.height);

// provide texture coordinates for the rectangle.
  var texcoordBuffer = gl.createBuffer();
  gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
      0.0,  0.0,
      1.0,  0.0,
      0.0,  1.0,
      0.0,  1.0,
      1.0,  0.0,
      1.0,  1.0,
  ]), gl.STATIC_DRAW);

// Create a texture.
  var texture = gl.createTexture();
  gl.bindTexture(gl.TEXTURE_2D, texture);

// Set the parameters so we can render any size image.
  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);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);

// Upload the image into the texture.
  gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);

// lookup uniforms
  var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
  var textureSizeLocation = gl.getUniformLocation(program, "u_textureSize");
  var kernelLocation = gl.getUniformLocation(program, "u_kernel[0]");
  var kernelWeightLocation = gl.getUniformLocation(program, "u_kernelWeight");

// Define several convolution kernels
  var kernels = {
    normal: [
      0, 0, 0,
      0, 1, 0,
      0, 0, 0
    ],
    gaussianBlur: [
      0.045, 0.122, 0.045,
      0.122, 0.332, 0.122,
      0.045, 0.122, 0.045
    ],
    gaussianBlur2: [
      1, 2, 1,
      2, 4, 2,
      1, 2, 1
    ],
    gaussianBlur3: [
      0, 1, 0,
      1, 1, 1,
      0, 1, 0
    ],
    unsharpen: [
      -1, -1, -1,
      -1,  9, -1,
      -1, -1, -1
    ],
    sharpness: [
       0,-1, 0,
      -1, 5,-1,
       0,-1, 0
    ],
    sharpen: [
       -1, -1, -1,
       -1, 16, -1,
       -1, -1, -1
    ],
    edgeDetect: [
       -0.125, -0.125, -0.125,
       -0.125,  1,     -0.125,
       -0.125, -0.125, -0.125
    ],
    edgeDetect2: [
       -1, -1, -1,
       -1,  8, -1,
       -1, -1, -1
    ],
    edgeDetect3: [
       -5, 0, 0,
        0, 0, 0,
        0, 0, 5
    ],
    edgeDetect4: [
       -1, -1, -1,
        0,  0,  0,
        1,  1,  1
    ],
    edgeDetect5: [
       -1, -1, -1,
        2,  2,  2,
       -1, -1, -1
    ],
    edgeDetect6: [
       -5, -5, -5,
       -5, 39, -5,
       -5, -5, -5
    ],
    sobelHorizontal: [
        1,  2,  1,
        0,  0,  0,
       -1, -2, -1
    ],
    sobelVertical: [
        1,  0, -1,
        2,  0, -2,
        1,  0, -1
    ],
    previtHorizontal: [
        1,  1,  1,
        0,  0,  0,
       -1, -1, -1
    ],
    previtVertical: [
        1,  0, -1,
        1,  0, -1,
        1,  0, -1
    ],
    boxBlur: [
        0.111, 0.111, 0.111,
        0.111, 0.111, 0.111,
        0.111, 0.111, 0.111
    ],
    triangleBlur: [
        0.0625, 0.125, 0.0625,
        0.125,  0.25,  0.125,
        0.0625, 0.125, 0.0625
    ],
    emboss: [
       -2, -1,  0,
       -1,  1,  1,
        0,  1,  2
    ]
  };
  var initialSelection = 'edgeDetect2';

// Setup UI to pick kernels.
  var ui = document.getElementById("ui");
  var select = document.createElement("select")
  for (var name in kernels) {
    var option = document.createElement("option");
    option.value = name;
    if (name == initialSelection) {
      option.selected = true;
    }
    option.appendChild(document.createTextNode(name));
    select.appendChild(option);
  }
  select.onchange = function(event) {
    drawWithKernel(this.options[this.selectedIndex].value);
  };
  ui.appendChild(select);
  drawWithKernel(initialSelection);

function computeKernelWeight(kernel) {
    var weight = kernel.reduce(function(prev, curr) {
        return prev + curr;
    });
    return weight <= 0 ? 1 : weight;
  }

function drawWithKernel(name) {
    webglUtils.resizeCanvasToDisplaySize(gl.canvas);

// Tell WebGL how to convert from clip space to pixels
    gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);

// Clear the canvas
    gl.clearColor(0, 0, 0, 0);
    gl.clear(gl.COLOR_BUFFER_BIT);

// Tell it to use our program (pair of shaders)
    gl.useProgram(program);

// Turn on the position attribute
    gl.enableVertexAttribArray(positionLocation);

// Bind the position buffer.
    gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);

// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
    var size = 2;          // 2 components per iteration
    var type = gl.FLOAT;   // the data is 32bit floats
    var normalize = false; // don't normalize the data
    var stride = 0;        // 0 = move forward size * sizeof(type) each iteration to get the next position
    var offset = 0;        // start at the beginning of the buffer
    gl.vertexAttribPointer(
        positionLocation, size, type, normalize, stride, offset)

// Turn on the teccord attribute
    gl.enableVertexAttribArray(texcoordLocation);

// Bind the position buffer.
    gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);

// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
    var size = 2;          // 2 components per iteration
    var type = gl.FLOAT;   // the data is 32bit floats
    var normalize = false; // don't normalize the data
    var stride = 0;        // 0 = move forward size * sizeof(type) each iteration to get the next position
    var offset = 0;        // start at the beginning of the buffer
    gl.vertexAttribPointer(
        texcoordLocation, size, type, normalize, stride, offset)

// set the resolution
    gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);

// set the size of the image
    gl.uniform2f(textureSizeLocation, image.width, image.height);

// set the kernel and it's weight
    gl.uniform1fv(kernelLocation, kernels[name]);
    gl.uniform1f(kernelWeightLocation, computeKernelWeight(kernels[name]));

// Draw the rectangle.
    var primitiveType = gl.TRIANGLES;
    var offset = 0;
    var count = 6;
    gl.drawArrays(primitiveType, offset, count);
  }
}

function setRectangle(gl, x, y, width, height) {
  var x1 = x;
  var x2 = x + width;
  var y1 = y;
  var y2 = y + height;
  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([
     x1, y1,
     x2, y1,
     x1, y2,
     x1, y2,
     x2, y1,
     x2, y2,
  ]), gl.STATIC_DRAW);
}

main();

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