<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>WebGL - 2D Image</title>
<link type="text/css" href="http://games.greggman.com/downloads/examples/webgl/resources/webgl-tutorials.css" rel="stylesheet" />
<script type="text/javascript" src="http://games.greggman.com/downloads/examples/webgl/resources/webgl-utils.js"></script>
<script>
window.onload = main;
function main() {
image = new Image();
image.src = "http://games.greggman.com/downloads/examples/webgl/resources/leaves.jpg"; // MUST BE SAME DOMAIN!!!
image.onload = function() {
setUp();
setInterval(function(){
x1 += 1;
y1 += 1
for (i = 0; i < 30; i++) {
for (e = 0; e < 10; e++) {
render(image, x1+i*5, y1+e*5);
}
}
},1000/60);
}
}
var x1 = 0;
var y1 = 0;
var image;
var canvas;
var gl;
var texture;
function setUp() {
canvas = document.getElementById("canvas");
gl = getWebGLContext(canvas);
// setup GLSL program
vertexShader = createShaderFromScriptElement(gl, "2d-vertex-shader");
fragmentShader = createShaderFromScriptElement(gl, "2d-fragment-shader");
program = createProgram(gl, [vertexShader, fragmentShader]);
gl.useProgram(program);
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
// set the resolution
gl.uniform2f(resolutionLocation, canvas.width, canvas.height);
// Create a texture.
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);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texCoordLocation = gl.getAttribLocation(program, "a_texCoord");
// 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);
gl.enableVertexAttribArray(texCoordLocation);
gl.vertexAttribPointer(texCoordLocation, 2, gl.FLOAT, false, 0, 0);
// Create a buffer for the position of the rectangle corners.
var buffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.enableVertexAttribArray(positionLocation);
gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);
}
function render(image, x, y) {
gl.bindTexture(gl.TEXTURE_2D, texture);
// Set a rectangle the same size as the image.
setRectangle(gl, x, y, image.width, image.height);
// Draw the rectangle.
gl.drawArrays(gl.TRIANGLES, 0, 6);
}
function randomInt(range) {
return Math.floor(Math.random() * range);
}
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);
}
</script>
<!-- vertex shader -->
<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>
<!-- fragment shader -->
<script id="2d-fragment-shader" type="x-shader/x-fragment">
precision mediump float;
// our texture
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
void main() {
gl_FragColor = texture2D(u_image, v_texCoord);
}
</script>
</head>
<body>
<canvas id="canvas" width="400" height="300"></canvas>
</body>
</html>
