Dither.cpp revision 44eb2c00861098dd3e2950d923646814b4cc57c2 
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
27Dither::Dither(Caches& caches)
28        : mCaches(caches)
29        , mInitialized(false)
30        , mDitherTexture(0) {
31}
32
33void Dither::bindDitherTexture() {
34    if (!mInitialized) {
35        bool useFloatTexture = Extensions::getInstance().hasFloatTextures();
36
37        glGenTextures(1, &mDitherTexture);
38        mCaches.textureState().bindTexture(mDitherTexture);
39
40        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
41        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
42
43        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
44        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
45
46        if (useFloatTexture) {
47            // We use a R16F texture, let's remap the alpha channel to the
48            // red channel to avoid changing the shader sampling code on GL ES 3.0+
49            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_A, GL_RED);
50
51            float dither = 1.0f / (255.0f * DITHER_KERNEL_SIZE * DITHER_KERNEL_SIZE);
52            const GLfloat pattern[] = {
53                 0 * dither,  8 * dither,  2 * dither, 10 * dither,
54                12 * dither,  4 * dither, 14 * dither,  6 * dither,
55                 3 * dither, 11 * dither,  1 * dither,  9 * dither,
56                15 * dither,  7 * dither, 13 * dither,  5 * dither
57            };
58
59            glPixelStorei(GL_UNPACK_ALIGNMENT, sizeof(GLfloat));
60            glTexImage2D(GL_TEXTURE_2D, 0, GL_R16F, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
61                    GL_RED, GL_FLOAT, &pattern);
62        } else {
63            const uint8_t pattern[] = {
64                 0,  8,  2, 10,
65                12,  4, 14,  6,
66                 3, 11,  1,  9,
67                15,  7, 13,  5
68            };
69
70            glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
71            glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
72                    GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
73        }
74
75        mInitialized = true;
76    } else {
77        mCaches.textureState().bindTexture(mDitherTexture);
78    }
79}
80
81void Dither::clear() {
82    if (mInitialized) {
83        mCaches.textureState().deleteTexture(mDitherTexture);
84        mInitialized = false;
85    }
86}
87
88///////////////////////////////////////////////////////////////////////////////
89// Program management
90///////////////////////////////////////////////////////////////////////////////
91
92void Dither::setupProgram(Program* program, GLuint* textureUnit) {
93    GLuint textureSlot = (*textureUnit)++;
94    mCaches.textureState().activateTexture(textureSlot);
95
96    bindDitherTexture();
97
98    glUniform1i(program->getUniform("ditherSampler"), textureSlot);
99}
100
101}; // namespace uirenderer
102}; // namespace android
103