wbalance.rs revision 572a5031a5d8602db0bec0b253428a034bd4dd59 
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 "ip.rsh"
18//#pragma rs_fp_relaxed
19
20static int histR[256] = {0}, histG[256] = {0}, histB[256] = {0};
21
22rs_allocation histogramSource;
23uint32_t histogramHeight;
24uint32_t histogramWidth;
25
26static float scaleR;
27static float scaleG;
28static float scaleB;
29
30static uchar4 estimateWhite() {
31
32    for (int i = 0; i < 256; i++) {
33        histR[i] = 0; histG[i] = 0; histB[i] = 0;
34    }
35
36    for (uint32_t i = 0; i < histogramHeight; i++) {
37        for (uint32_t j = 0; j < histogramWidth; j++) {
38            uchar4 in = rsGetElementAt_uchar4(histogramSource, j, i);
39            histR[in.r]++;
40            histG[in.g]++;
41            histB[in.b]++;
42        }
43    }
44
45    int min_r = -1, min_g = -1, min_b = -1;
46    int max_r =  0, max_g =  0, max_b =  0;
47    int sum_r =  0, sum_g =  0, sum_b =  0;
48
49    for (int i = 1; i < 255; i++) {
50        int r = histR[i];
51        int g = histG[i];
52        int b = histB[i];
53        sum_r += r;
54        sum_g += g;
55        sum_b += b;
56
57        if (r>0){
58            if (min_r < 0) min_r = i;
59            max_r = i;
60        }
61        if (g>0){
62            if (min_g < 0) min_g = i;
63            max_g = i;
64        }
65        if (b>0){
66            if (min_b < 0) min_b = i;
67            max_b = i;
68        }
69    }
70
71    int sum15r = 0, sum15g = 0, sum15b = 0;
72    int count15r = 0, count15g = 0, count15b = 0;
73    int tmp_r = 0, tmp_g = 0, tmp_b = 0;
74
75    for (int i = 254; i >0; i--) {
76        int r = histR[i];
77        int g = histG[i];
78        int b = histB[i];
79        tmp_r += r;
80        tmp_g += g;
81        tmp_b += b;
82
83        if ((tmp_r > sum_r/20) && (tmp_r < sum_r/5)) {
84            sum15r += r*i;
85            count15r += r;
86        }
87        if ((tmp_g > sum_g/20) && (tmp_g < sum_g/5)) {
88            sum15g += g*i;
89            count15g += g;
90        }
91        if ((tmp_b > sum_b/20) && (tmp_b < sum_b/5)) {
92            sum15b += b*i;
93            count15b += b;
94        }
95
96    }
97
98    uchar4 out;
99
100    if ((count15r>0) && (count15g>0) && (count15b>0) ){
101        out.r = sum15r/count15r;
102        out.g = sum15g/count15g;
103        out.b = sum15b/count15b;
104    }else {
105        out.r = out.g = out.b = 255;
106    }
107
108    return out;
109
110}
111
112void prepareWhiteBalance() {
113    uchar4 estimation = estimateWhite();
114    int minimum = min(estimation.r, min(estimation.g, estimation.b));
115    int maximum = max(estimation.r, max(estimation.g, estimation.b));
116    float avg = (minimum + maximum) / 2.f;
117
118    scaleR =  avg/estimation.r;
119    scaleG =  avg/estimation.g;
120    scaleB =  avg/estimation.b;
121
122}
123
124static unsigned char contrastClamp(int c)
125{
126    int N = 255;
127    c &= ~(c >> 31);
128    c -= N;
129    c &= (c >> 31);
130    c += N;
131    return  (unsigned char) c;
132}
133
134void whiteBalanceKernel(const uchar4 *in, uchar4 *out) {
135    float Rc =  in->r*scaleR;
136    float Gc =  in->g*scaleG;
137    float Bc =  in->b*scaleB;
138
139    out->r = contrastClamp(Rc);
140    out->g = contrastClamp(Gc);
141    out->b = contrastClamp(Bc);
142}
143