Dither.cpp revision 2de7771740ee08fcaff638ec6b2e460bb72fff04 
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        glGenTextures(1, &mDitherTexture);
36        mCaches.textureState().bindTexture(mDitherTexture);
37
38        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
39        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
40
41        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
42        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
43
44        if (mCaches.extensions().hasFloatTextures()) {
45            // We use a R16F texture, let's remap the alpha channel to the
46            // red channel to avoid changing the shader sampling code on GL ES 3.0+
47            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_A, GL_RED);
48
49            float dither = 1.0f / (255.0f * DITHER_KERNEL_SIZE * DITHER_KERNEL_SIZE);
50            const GLfloat pattern[] = {
51                 0 * dither,  8 * dither,  2 * dither, 10 * dither,
52                12 * dither,  4 * dither, 14 * dither,  6 * dither,
53                 3 * dither, 11 * dither,  1 * dither,  9 * dither,
54                15 * dither,  7 * dither, 13 * dither,  5 * dither
55            };
56
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            glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
68                    GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
69        }
70
71        mInitialized = true;
72    } else {
73        mCaches.textureState().bindTexture(mDitherTexture);
74    }
75}
76
77void Dither::clear() {
78    if (mInitialized) {
79        mCaches.textureState().deleteTexture(mDitherTexture);
80        mInitialized = false;
81    }
82}
83
84///////////////////////////////////////////////////////////////////////////////
85// Program management
86///////////////////////////////////////////////////////////////////////////////
87
88void Dither::setupProgram(Program& program, GLuint* textureUnit) {
89    GLuint textureSlot = (*textureUnit)++;
90    mCaches.textureState().activateTexture(textureSlot);
91
92    bindDitherTexture();
93
94    glUniform1i(program.getUniform("ditherSampler"), textureSlot);
95}
96
97}; // namespace uirenderer
98}; // namespace android
99