Dither.cpp revision 4abab937bf3f168763a7c029275bf1de151ec1ae 
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// Lifecycle
25///////////////////////////////////////////////////////////////////////////////
26
27void Dither::bindDitherTexture() {
28    if (!mInitialized) {
29        bool useFloatTexture = Extensions::getInstance().getMajorGlVersion() >= 3;
30
31        glGenTextures(1, &mDitherTexture);
32        glBindTexture(GL_TEXTURE_2D, mDitherTexture);
33
34        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
35        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
36
37        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
38        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
39
40        if (useFloatTexture) {
41            // We use a R16F texture, let's remap the alpha channel to the
42            // red channel to avoid changing the shader sampling code on GL ES 3.0+
43            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_A, GL_RED);
44
45            float dither = 1.0f / (255.0f * DITHER_KERNEL_SIZE * DITHER_KERNEL_SIZE);
46            const GLfloat pattern[] = {
47                 0 * dither,  8 * dither,  2 * dither, 10 * dither,
48                12 * dither,  4 * dither, 14 * dither,  6 * dither,
49                 3 * dither, 11 * dither,  1 * dither,  9 * dither,
50                15 * dither,  7 * dither, 13 * dither,  5 * dither
51            };
52
53            glPixelStorei(GL_UNPACK_ALIGNMENT, sizeof(GLfloat));
54            glTexImage2D(GL_TEXTURE_2D, 0, GL_R16F, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
55                    GL_RED, GL_FLOAT, &pattern);
56        } else {
57            const uint8_t pattern[] = {
58                 0,  8,  2, 10,
59                12,  4, 14,  6,
60                 3, 11,  1,  9,
61                15,  7, 13,  5
62            };
63
64            glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
65            glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
66                    GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
67        }
68
69        mInitialized = true;
70    } else {
71        glBindTexture(GL_TEXTURE_2D, mDitherTexture);
72    }
73}
74
75void Dither::clear() {
76    if (mInitialized) {
77        glDeleteTextures(1, &mDitherTexture);
78        mInitialized = false;
79    }
80}
81
82///////////////////////////////////////////////////////////////////////////////
83// Program management
84///////////////////////////////////////////////////////////////////////////////
85
86void Dither::setupProgram(Program* program, GLuint* textureUnit) {
87    GLuint textureSlot = (*textureUnit)++;
88    Caches::getInstance().activeTexture(textureSlot);
89
90    bindDitherTexture();
91
92    glUniform1i(program->getUniform("ditherSampler"), textureSlot);
93}
94
95}; // namespace uirenderer
96}; // namespace android
97