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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include "Caches.h"
     18 #include "Dither.h"
     19 
     20 namespace android {
     21 namespace uirenderer {
     22 
     23 ///////////////////////////////////////////////////////////////////////////////
     24 // Lifecycle
     25 ///////////////////////////////////////////////////////////////////////////////
     26 
     27 Dither::Dither(): mCaches(NULL), mInitialized(false), mDitherTexture(0) {
     28 }
     29 
     30 void Dither::bindDitherTexture() {
     31     if (!mInitialized) {
     32         bool useFloatTexture = Extensions::getInstance().hasFloatTextures();
     33 
     34         glGenTextures(1, &mDitherTexture);
     35         mCaches->bindTexture(mDitherTexture);
     36 
     37         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
     38         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     39 
     40         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
     41         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
     42 
     43         if (useFloatTexture) {
     44             // We use a R16F texture, let's remap the alpha channel to the
     45             // red channel to avoid changing the shader sampling code on GL ES 3.0+
     46             glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_A, GL_RED);
     47 
     48             float dither = 1.0f / (255.0f * DITHER_KERNEL_SIZE * DITHER_KERNEL_SIZE);
     49             const GLfloat pattern[] = {
     50                  0 * dither,  8 * dither,  2 * dither, 10 * dither,
     51                 12 * dither,  4 * dither, 14 * dither,  6 * dither,
     52                  3 * dither, 11 * dither,  1 * dither,  9 * dither,
     53                 15 * dither,  7 * dither, 13 * dither,  5 * dither
     54             };
     55 
     56             glPixelStorei(GL_UNPACK_ALIGNMENT, sizeof(GLfloat));
     57             glTexImage2D(GL_TEXTURE_2D, 0, GL_R16F, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
     58                     GL_RED, GL_FLOAT, &pattern);
     59         } else {
     60             const uint8_t pattern[] = {
     61                  0,  8,  2, 10,
     62                 12,  4, 14,  6,
     63                  3, 11,  1,  9,
     64                 15,  7, 13,  5
     65             };
     66 
     67             glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
     68             glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
     69                     GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
     70         }
     71 
     72         mInitialized = true;
     73     } else {
     74         mCaches->bindTexture(mDitherTexture);
     75     }
     76 }
     77 
     78 void Dither::clear() {
     79     if (mInitialized) {
     80         mCaches->deleteTexture(mDitherTexture);
     81         mInitialized = false;
     82     }
     83 }
     84 
     85 ///////////////////////////////////////////////////////////////////////////////
     86 // Program management
     87 ///////////////////////////////////////////////////////////////////////////////
     88 
     89 void Dither::setupProgram(Program* program, GLuint* textureUnit) {
     90     if (!mCaches) mCaches = &Caches::getInstance();
     91 
     92     GLuint textureSlot = (*textureUnit)++;
     93     mCaches->activeTexture(textureSlot);
     94 
     95     bindDitherTexture();
     96 
     97     glUniform1i(program->getUniform("ditherSampler"), textureSlot);
     98 }
     99 
    100 }; // namespace uirenderer
    101 }; // namespace android
    102