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