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<!--
O3D YUV to RGB conversion Tutorial
In this sample we convert from a Y'UV420p encoded video frame to an
RGB texture using a shader to do the conversion on the video hardware.
-->
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>YUV to RGB Conversion in a shader.</title>
<script type="text/javascript" src="o3djs/base.js"></script>
<script type="text/javascript">
o3djs.require('o3djs.util');
o3djs.require('o3djs.math');
o3djs.require('o3djs.rendergraph');
o3djs.require('o3djs.primitives');
o3djs.require('o3djs.effect');
o3djs.require('o3djs.io');
// Events
// Run the init() once the page has finished loading.
window.onload = init;
// global variables
var g_o3d;
var g_math;
var g_client;
var g_pack;
var g_viewInfo;
var g_finished = false; // for selenium testing
Creates the client area and sets up the secondary init entry point.
function init() {
o3djs.util.makeClients(initStep2);
}
Initializes O3D, loads the effect, and draws the quad that
will display the texture.
parameter: {Array} clientElements Array of o3d object elements.
function initStep2(clientElements) {
// Initialize global variables and libraries.
var o3dElement = clientElements[0];
g_o3d = o3dElement.o3d;
g_math = o3djs.math;
g_client = o3dElement.client;
// Create a pack to manage our resources/assets
g_pack = g_client.createPack();
// Create the render graph for a view.
g_viewInfo = o3djs.rendergraph.createBasicView(
g_pack,
g_client.root,
g_client.renderGraphRoot);
// Setup an orthographic projection
// Offset by half a pixel to avoid roundoff errors.
g_viewInfo.drawContext.projection = g_math.matrix4.orthographic(
-g_client.width * 0.5 + 0.5,
g_client.width * 0.5 + 0.5,
-g_client.height * 0.5 - 0.5,
g_client.height * 0.5 - 0.5,
0.1,
1000);
g_viewInfo.drawContext.view = g_math.matrix4.lookAt(
[0, 500, 0],
[0, 0, 0],
[0, 0, -1]);
// Create and load the effect and the shader.
var effect = g_pack.createObject('Effect');
o3djs.effect.loadEffect(effect, 'shaders/yuv2rgb.shader');
// Create a Material for the effect.
var myMaterial = g_pack.createObject('Material');
// Set the material's drawList
myMaterial.drawList = g_viewInfo.performanceDrawList;
// Apply our effect to this material.
myMaterial.effect = effect;
// Create the params the effect needs on the material.
effect.createUniformParameters(myMaterial);
// Creates a quad using the effect that has a 1:1 aspect ratio.
var myShape = o3djs.primitives.createPlane(g_pack,
myMaterial,
720, // width
720, // height
1, // quads across
1); // quads down
// Get the material's sampler parameter
var sampler_param = myMaterial.getParam('textureSampler');
var sampler = g_pack.createObject('Sampler');
sampler.addressModeU = g_o3d.Sampler.WRAP;
sampler.addressModeV = g_o3d.Sampler.WRAP;
sampler.magFilter = g_o3d.Sampler.POINT;
sampler.minFilter = g_o3d.Sampler.POINT;
// Be sure to turn off MIP-mapping, since that causes problems when
// jumping around the image the way we are.
sampler.mipFilter = g_o3d.Sampler.NONE;
sampler_param.value = sampler;
// Set the source image width
var width_param = myMaterial.getParam('imageWidth');
width_param.value = 720.0;
// Set the source image height
var height_param = myMaterial.getParam('imageHeight');
height_param.value = 486.0;
// Load our Y'UV420p texture, encoded as a greyscale PNG image. This
// happens asynchronously.
var url = o3djs.util.getCurrentURI() + 'assets/shaving_cream.png';
o3djs.io.loadTexture(g_pack, url, function(texture, exception) {
if (exception) {
alert(exception);
return;
}
sampler.texture = texture;
// adjust the scale of our transform to match the aspect ratio of
// the texture. Of course we could also have waited until now to build
// our quad and set its width and height to match instead of scaling
// here.
var textureWidth = texture.width;
// Account for additional data on bottom of image.
var textureHeight = texture.height * 2.0 / 3.0;
var hScale = 1;
var vScale = 1;
if (textureWidth > textureHeight) {
vScale = textureHeight / textureWidth;
} else if (textureHeight > textureWidth) {
hScale = textureWidth / textureHeight;
}
// We now attach our quad to the root of the transform graph. We do
// this after the texture has loaded, otherwise we'd be attempting
// to display something invalid.
var root = g_client.root;
root.addShape(myShape);
root.scale(hScale, 1, vScale);
g_finished = true; // for selenium testing.
});
}
</script>
</head>
<body>
<h1>YUV to RGB Conversion</h1>
<p>This how to do image colorspace and format conversion in a shader.</p>
<p>Here is the YUV encoded image (treated as an 8-bit greyscale image):</p>
<p><img src="assets/shaving_cream.png" style="width: 720px; height: 729px"
alt="YUV encoded image"/></p>
<p>Here is the original image, encoded as a JPEG image:</p>
<p><img src="assets/shaving_cream.jpg" style="width: 720px; height: 486px"
alt="Original JPG encoded image"/></p>
<p>Here is the O3D plugin loading the YUV image, and converting it
to RGB in the shader on the fly.</p>
<!-- Start of O3D plugin -->
<div id="o3d" style="width: 720px; height: 486px"></div>
<!-- End of O3D plugin -->
</body>
</html>
(C) Æliens
20/2/2008
You may not copy or print any of this material without explicit permission of the author or the publisher.
In case of other copyright issues, contact the author.
