webgl-fundamentals/webgl/webgl-2d-image-red2blue.html at master · gfxfundamentals/webgl-fundamentals · GitHub

Name: webgl-fundamentals/webgl/webgl-2d-image-red2blue.html at master · gfxfundamentals/webgl-fundamentals · GitHub
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<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
<head>
<metacharset="utf-8">
<metaname="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
<title>WebGL - 2D Image Swap Red and Blue</title>
<linktype="text/css" href="resources/webgl-tutorials.css" rel="stylesheet" />
</head>
<body>
<canvasid="canvas"></canvas>
</body>
<!-- vertex shader -->
<scriptid="vertex-shader-2d" type="x-shader/x-vertex">
attributevec2a_position;
attributevec2a_texCoord;

uniformvec2u_resolution;

varyingvec2v_texCoord;

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

// convert from 0->1 to 0->2
vec2zeroToTwo=zeroToOne*2.0;

// convert from 0->2 to -1->+1 (clipspace)
vec2clipSpace=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>
<!-- fragment shader -->
<scriptid="fragment-shader-2d" type="x-shader/x-fragment">
precisionmediumpfloat;

// our texture
uniformsampler2Du_image;

// the texCoords passed in from the vertex shader.
varyingvec2v_texCoord;

voidmain(){
gl_FragColor=texture2D(u_image,v_texCoord).bgra;
}
</script>
<!--
for most samples webgl-utils only provides shader compiling/linking and
canvas resizing because why clutter the examples with code that's the same in every sample.
See https://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
and https://webglfundamentals.org/webgl/lessons/webgl-resizing-the-canvas.html
for webgl-utils, m3, m4, and webgl-lessons-ui.
-->
<scriptsrc="resources/webgl-utils.js"></script>
<script>
"use strict";

functionmain(){
varimage=newImage();
image.src="resources/leaves.jpg";
image.onload=function(){
render(image);
};
}

functionrender(image){
// Get A WebGL context
/** @type {HTMLCanvasElement} */
varcanvas=document.querySelector("#canvas");
vargl=canvas.getContext("webgl");
if(!gl){
return;
}

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

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

// Create a buffer to put three 2d clip space points in
varpositionBuffer=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.
vartexcoordBuffer=gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER,texcoordBuffer);
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array([
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.
vartexture=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
varresolutionLocation=gl.getUniformLocation(program,"u_resolution");

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)
varsize=2;// 2 components per iteration
vartype=gl.FLOAT;// the data is 32bit floats
varnormalize=false;// don't normalize the data
varstride=0;// 0 = move forward size * sizeof(type) each iteration to get the next position
varoffset=0;// start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation,size,type,normalize,stride,offset);

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

// bind the texcoord buffer.
gl.bindBuffer(gl.ARRAY_BUFFER,texcoordBuffer);

// Tell the texcoord attribute how to get data out of texcoordBuffer (ARRAY_BUFFER)
varsize=2;// 2 components per iteration
vartype=gl.FLOAT;// the data is 32bit floats
varnormalize=false;// don't normalize the data
varstride=0;// 0 = move forward size * sizeof(type) each iteration to get the next position
varoffset=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);

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

functionsetRectangle(gl,x,y,width,height){
varx1=x;
varx2=x+width;
vary1=y;
vary2=y+height;
gl.bufferData(gl.ARRAY_BUFFER,newFloat32Array([
x1,y1,
x2,y1,
x1,y2,
x1,y2,
x2,y1,
x2,y2,
]),gl.STATIC_DRAW);
}

main();
</script>
</html>