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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 // Defines
     25 ///////////////////////////////////////////////////////////////////////////////
     26 
     27 // Must be a power of two
     28 #define DITHER_KERNEL_SIZE 4
     29 
     30 ///////////////////////////////////////////////////////////////////////////////
     31 // Lifecycle
     32 ///////////////////////////////////////////////////////////////////////////////
     33 
     34 void Dither::bindDitherTexture() {
     35     if (!mInitialized) {
     36         const uint8_t pattern[] = {
     37              0,  8,  2, 10,
     38             12,  4, 14,  6,
     39              3, 11,  1,  9,
     40             15,  7, 13,  5
     41         };
     42 
     43         glGenTextures(1, &mDitherTexture);
     44         glBindTexture(GL_TEXTURE_2D, mDitherTexture);
     45 
     46         glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
     47 
     48         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
     49         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
     50 
     51         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
     52         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
     53 
     54         glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
     55                 GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
     56 
     57         mInitialized = true;
     58     } else {
     59         glBindTexture(GL_TEXTURE_2D, mDitherTexture);
     60     }
     61 }
     62 
     63 void Dither::clear() {
     64     if (mInitialized) {
     65         glDeleteTextures(1, &mDitherTexture);
     66     }
     67 }
     68 
     69 ///////////////////////////////////////////////////////////////////////////////
     70 // Program management
     71 ///////////////////////////////////////////////////////////////////////////////
     72 
     73 void Dither::setupProgram(Program* program, GLuint* textureUnit) {
     74     GLuint textureSlot = (*textureUnit)++;
     75     Caches::getInstance().activeTexture(textureSlot);
     76 
     77     bindDitherTexture();
     78 
     79     float ditherSize = 1.0f / DITHER_KERNEL_SIZE;
     80     glUniform1i(program->getUniform("ditherSampler"), textureSlot);
     81     glUniform1f(program->getUniform("ditherSize"), ditherSize);
     82     glUniform1f(program->getUniform("ditherSizeSquared"), ditherSize * ditherSize);
     83 }
     84 
     85 }; // namespace uirenderer
     86 }; // namespace android
     87