Dither.cpp revision a1d12dd619c86c9ac121a3095ff5e5633c11e876 
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
20namespace android {
21namespace 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
34void 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
63void Dither::clear() {
64    if (mInitialized) {
65        glDeleteTextures(1, &mDitherTexture);
66    }
67}
68
69///////////////////////////////////////////////////////////////////////////////
70// Program management
71///////////////////////////////////////////////////////////////////////////////
72
73void 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