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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" id="o3dscript">
o3djs.require('o3djs.util');
o3djs.require('o3djs.math');
o3djs.require('o3djs.rendergraph');
o3djs.require('o3djs.primitives');
o3djs.require('o3djs.material');
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.
 *
 * @param {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 a material.
  var myMaterial = o3djs.material.createMaterialFromFile(
      g_pack,
      'shaders/yuv2rgb.shader',
      g_viewInfo.performanceDrawList);

  // 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>