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 
20 namespace android {
21 namespace uirenderer {
22 
23 ///////////////////////////////////////////////////////////////////////////////
24 // Lifecycle
25 ///////////////////////////////////////////////////////////////////////////////
26 
Dither(Caches & caches)27 Dither::Dither(Caches& caches)
28         : mCaches(caches)
29         , mInitialized(false)
30         , mDitherTexture(0) {
31 }
32 
bindDitherTexture()33 void 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             glPixelStorei(GL_UNPACK_ALIGNMENT, sizeof(GLfloat));
58             glTexImage2D(GL_TEXTURE_2D, 0, GL_R16F, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
59                     GL_RED, GL_FLOAT, &pattern);
60         } else {
61             const uint8_t pattern[] = {
62                  0,  8,  2, 10,
63                 12,  4, 14,  6,
64                  3, 11,  1,  9,
65                 15,  7, 13,  5
66             };
67 
68             glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
69             glTexImage2D(GL_TEXTURE_2D, 0, GL_ALPHA, DITHER_KERNEL_SIZE, DITHER_KERNEL_SIZE, 0,
70                     GL_ALPHA, GL_UNSIGNED_BYTE, &pattern);
71         }
72 
73         mInitialized = true;
74     } else {
75         mCaches.textureState().bindTexture(mDitherTexture);
76     }
77 }
78 
clear()79 void Dither::clear() {
80     if (mInitialized) {
81         mCaches.textureState().deleteTexture(mDitherTexture);
82         mInitialized = false;
83     }
84 }
85 
86 ///////////////////////////////////////////////////////////////////////////////
87 // Program management
88 ///////////////////////////////////////////////////////////////////////////////
89 
setupProgram(Program & program,GLuint * textureUnit)90 void Dither::setupProgram(Program& program, GLuint* textureUnit) {
91     GLuint textureSlot = (*textureUnit)++;
92     mCaches.textureState().activateTexture(textureSlot);
93 
94     bindDitherTexture();
95 
96     glUniform1i(program.getUniform("ditherSampler"), textureSlot);
97 }
98 
99 }; // namespace uirenderer
100 }; // namespace android
101