| /* |
| * Copyright 2010, Google Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| /* |
| * This is a conversion of a conversion of a cg shader from Chrome: |
| * http://src.chromium.org/viewvc/chrome/trunk/src/o3d/samples/shaders/yuv2rgb.shader |
| */ |
| |
| /* |
| * This shader takes a Y'UV420p image as a single greyscale plane, and |
| * converts it to RGB by sampling the correct parts of the image, and |
| * by converting the colorspace to RGB on the fly. |
| */ |
| |
| /* |
| * These represent the image dimensions of the SOURCE IMAGE (not the |
| * Y'UV420p image). This is the same as the dimensions of the Y' |
| * portion of the Y'UV420p image. They are set from JavaScript. |
| */ |
| uniform float imageWidth; |
| uniform float imageHeight; |
| |
| /* |
| * This is the texture sampler where the greyscale Y'UV420p image is |
| * accessed. |
| */ |
| uniform sampler2D textureSampler; |
| |
| #if defined (USE_UNIFORM_MATRIX) |
| uniform mat4 conversion; |
| #endif |
| |
| varying vec4 v1; |
| |
| /** |
| * Given the texture coordinates, our pixel shader grabs the right |
| * value from each channel of the source image, converts it from Y'UV |
| * to RGB, and returns the result. |
| * |
| * Each Y texel provides luminance information for one pixel in the image. |
| * Each U and V texel provides color information for a 2x2 block of pixels. |
| * The U and V texels are just appended to the Y texels. |
| * |
| * For images that have a height divisible by 4, things work out nicely. |
| * For images that are merely divisible by 2, it's not so nice |
| * (and YUV420 doesn't work for image sizes not divisible by 2). |
| * |
| * Here is a 6x6 image, with the layout of the planes of U and V. |
| * Notice that the V plane starts halfway through the last scanline |
| * that has U on it. |
| * |
| * 0 +---+---+---+---+---+---+ |
| * | Y0| Y0| Y1| Y1| Y2| Y2| |
| * +---+---+---+---+---+---+ |
| * | Y0| Y0| Y1| Y1| Y2| Y2| |
| * +---+---+---+---+---+---+ |
| * | Y3| Y3| Y4| Y4| Y5| Y5| |
| * +---+---+---+---+---+---+ |
| * | Y3| Y3| Y4| Y4| Y5| Y5| |
| * +---+---+---+---+---+---+ |
| * | Y6| Y6| Y7| Y7| Y8| Y8| |
| * +---+---+---+---+---+---+ |
| * | Y6| Y6| Y7| Y7| Y8| Y8| |
| *2/3 +---+---+---+---+---+---+ |
| * | U0| U1| U2| U3| U4| U5| |
| * +---+---+---+---+---+---+ |
| *5/6 | U6| U7| U8| V0| V1| V2| |
| * +---+---+---+---+---+---+ |
| * | V3| V4| V5| V6| V7| V8| |
| * 1 +---+---+---+---+---+---+ |
| * 0 0.5 1 |
| * |
| * Here is a 4x4 image, where the U and V planes are nicely split into |
| * separable blocks. |
| * |
| * 0 +---+---+---+---+ |
| * | Y0| Y0| Y1| Y1| |
| * +---+---+---+---+ |
| * | Y0| Y0| Y1| Y1| |
| * +---+---+---+---+ |
| * | Y2| Y2| Y3| Y3| |
| * +---+---+---+---+ |
| * | Y2| Y2| Y3| Y3| |
| *2/3 +---+---+---+---+ |
| * | U0| U1| U2| U3| |
| *5/6 +---+---+---+---+ |
| * | V0| V1| V2| V3| |
| * 1 +---+---+---+---+ |
| * 0 0.5 1 |
| * |
| * The number in a cell indicates which U and V values map onto |
| * the cell: Un and Vn are used to color the four 'n' cells. As the |
| * image is drawn its texture coordinates range from 0 to 1. The 'y' |
| * coordinate is scaled by 2/3 to map from the Y texels, scaled by 1/6 |
| * and shifted down 2/3 to map from the U texels, and scaled by 1/6 |
| * and shifted down 5/6 to map from the V texels. To map from U or V |
| * texels the 'x' coordinate is scaled by 1/2 always and shifted right |
| * 1/2 when needed. For example rows 0 and 1 use left side U texels |
| * (U0-U2 in the first example) while rows 2 and 3 right side U texels |
| * (U3-U5 in the first example), and so on for the remaining rows. |
| * When the image height is a multiple of 4, the 'V side' is the same |
| * as the 'U side,' otherwise it is opposite. |
| */ |
| |
| |
| void main() { |
| float uside, vside; |
| |
| // texture origin at top left, vertex origin at bottom left |
| vec2 t = vec2(v1.x, (1. - v1.y)); |
| |
| // y position in pixels |
| float ypixel = floor(t.y * imageHeight); |
| |
| if (mod(ypixel, 4.) < 2.) { |
| // rows 0-1, U on left side |
| uside = 0.; |
| } else { |
| // rows 2-3, U on right side |
| uside = .5; |
| } |
| |
| if (mod(imageHeight, 4.) == 0.) { |
| // multiple of 4, V same side as U |
| vside = uside; |
| } else { |
| // assume multiple of 2, V opposite side to U |
| vside = .5 - uside; |
| } |
| |
| // shrink y tex. coord. by 2/3 to cover Y section |
| vec2 y = t * vec2(1., 2./3.); |
| |
| // for U and V shrink x tex. coord. by 0.5, y by 1/6 |
| t *= vec2(.5, 1./6.); |
| |
| // shift to proper side and translate down... |
| vec2 u = t + vec2(uside, 2./3.); // ...to U section |
| vec2 v = t + vec2(vside, 5./6.); // ...to V section |
| |
| float yChannel = texture2D(textureSampler, y).x; |
| float uChannel = texture2D(textureSampler, u).x; |
| float vChannel = texture2D(textureSampler, v).x; |
| |
| /* |
| * This does the colorspace conversion from Y'UV to RGB as a matrix |
| * multiply. It also does the offset of the U and V channels from |
| * [0,1] to [-.5,.5] as part of the transform. |
| */ |
| vec4 channels = vec4(yChannel, uChannel, vChannel, 1.0); |
| #if !defined(USE_UNIFORM_MATRIX) |
| mat4 conversion = mat4( 1.0, 1.0, 1.0, 0.0, |
| 0.0, -0.344, 1.772, 0.0, |
| 1.402, -0.714, 0.0, 0.0, |
| -0.701, 0.529, -0.886, 1.0); |
| #endif |
| |
| gl_FragColor = conversion * channels; |
| } |