1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Copyright (C) 2021, Ideas On Board
*
* awb.cpp - AWB control algorithm
*/
#include "awb.h"
#include <algorithm>
#include <cmath>
#include <libcamera/base/log.h>
/**
* \file awb.h
*/
namespace libcamera {
namespace ipa::ipu3::algorithms {
LOG_DEFINE_CATEGORY(IPU3Awb)
/*
* When zones are used for the grey world algorithm, they are only considered if
* their average green value is at least 16/255 (after black level subtraction)
* to exclude zones that are too dark and don't provide relevant colour
* information (on the opposite side of the spectrum, saturated regions are
* excluded by the ImgU statistics engine).
*/
static constexpr uint32_t kMinGreenLevelInZone = 16;
/*
* Minimum proportion of non-saturated cells in a zone for the zone to be used
* by the AWB algorithm.
*/
static constexpr double kMaxCellSaturationRatio = 0.8;
/*
* Maximum ratio of saturated pixels in a cell for the cell to be considered
* non-saturated and counted by the AWB algorithm.
*/
static constexpr uint32_t kMinCellsPerZoneRatio = 255 * 90 / 100;
/**
* \struct Accumulator
* \brief RGB statistics for a given zone
*
* Accumulate red, green and blue values for each non-saturated item over a
* zone. Items can for instance be pixels, but also the average of groups of
* pixels, depending on who uses the accumulator.
* \todo move this description and structure into a common header
*
* Zones which are saturated beyond the threshold defined in
* ipu3_uapi_awb_config_s are not included in the average.
*
* \var Accumulator::counted
* \brief Number of unsaturated cells used to calculate the sums
*
* \var Accumulator::sum
* \brief A structure containing the average red, green and blue sums
*
* \var Accumulator::sum.red
* \brief Sum of the average red values of each unsaturated cell in the zone
*
* \var Accumulator::sum.green
* \brief Sum of the average green values of each unsaturated cell in the zone
*
* \var Accumulator::sum.blue
* \brief Sum of the average blue values of each unsaturated cell in the zone
*/
/**
* \struct Awb::AwbStatus
* \brief AWB parameters calculated
*
* The AwbStatus structure is intended to store the AWB
* parameters calculated by the algorithm
*
* \var AwbStatus::temperatureK
* \brief Color temperature calculated
*
* \var AwbStatus::redGain
* \brief Gain calculated for the red channel
*
* \var AwbStatus::greenGain
* \brief Gain calculated for the green channel
*
* \var AwbStatus::blueGain
* \brief Gain calculated for the blue channel
*/
/* Default settings for Bayer noise reduction replicated from the Kernel */
static const struct ipu3_uapi_bnr_static_config imguCssBnrDefaults = {
.wb_gains = { 16, 16, 16, 16 },
.wb_gains_thr = { 255, 255, 255, 255 },
.thr_coeffs = { 1700, 0, 31, 31, 0, 16 },
.thr_ctrl_shd = { 26, 26, 26, 26 },
.opt_center = { -648, 0, -366, 0 },
.lut = {
{ 17, 23, 28, 32, 36, 39, 42, 45,
48, 51, 53, 55, 58, 60, 62, 64,
66, 68, 70, 72, 73, 75, 77, 78,
80, 82, 83, 85, 86, 88, 89, 90 } },
.bp_ctrl = { 20, 0, 1, 40, 0, 6, 0, 6, 0 },
.dn_detect_ctrl = { 9, 3, 4, 0, 8, 0, 1, 1, 1, 1, 0 },
.column_size = 1296,
.opt_center_sqr = { 419904, 133956 },
};
/* Default color correction matrix defined as an identity matrix */
static const struct ipu3_uapi_ccm_mat_config imguCssCcmDefault = {
8191, 0, 0, 0,
0, 8191, 0, 0,
0, 0, 8191, 0
};
/**
* \class Awb
* \brief A Grey world white balance correction algorithm
*
* The Grey World algorithm assumes that the scene, in average, is neutral grey.
* Reference: Lam, Edmund & Fung, George. (2008). Automatic White Balancing in
* Digital Photography. 10.1201/9781420054538.ch10.
*
* The IPU3 generates statistics from the Bayer Down Scaler output into a grid
* defined in the ipu3_uapi_awb_config_s structure.
*
* - Cells are defined in Pixels
* - Zones are defined in Cells
*
* 80 cells
* /───────────── 1280 pixels ───────────\
* 16 zones
* 16
* ┌────┬────┬────┬────┬────┬─ ──────┬────┐ \
* │Cell│ │ │ │ │ | │ │ │
* 16 │ px │ │ │ │ │ | │ │ │
* ├────┼────┼────┼────┼────┼─ ──────┼────┤ │
* │ │ │ │ │ │ | │ │
* │ │ │ │ │ │ | │ │ 7
* │ ── │ ── │ ── │ ── │ ── │ ── ── ─┤ ── │ 1 2 4
* │ │ │ │ │ │ | │ │ 2 0 5
*
* │ │ │ │ │ │ | │ │ z p c
* ├────┼────┼────┼────┼────┼─ ──────┼────┤ o i e
* │ │ │ │ │ │ | │ │ n x l
* │ │ | │ │ e e l
* ├─── ───┼─ ──────┼────┤ s l s
* │ │ | │ │ s
* │ │ | │ │
* ├─── Zone of Cells ───┼─ ──────┼────┤ │
* │ (5 x 4) │ | │ │ │
* │ │ | │ │ │
* ├── ───┼─ ──────┼────┤ │
* │ │ │ | │ │ │
* │ │ │ │ │ │ | │ │ │
* └────┴────┴────┴────┴────┴─ ──────┴────┘ /
*
*
* In each cell, the ImgU computes for each colour component the average of all
* unsaturated pixels (below a programmable threshold). It also provides the
* ratio of saturated pixels in the cell.
*
* The AWB algorithm operates on a coarser grid, made by grouping cells from the
* hardware grid into zones. The number of zones is fixed to \a kAwbStatsSizeX x
* \a kAwbStatsSizeY. For example, a frame of 1280x720 is divided into 80x45
* cells of [16x16] pixels and 16x12 zones of [5x4] cells each
* (\a kAwbStatsSizeX=16 and \a kAwbStatsSizeY=12). If the number of cells isn't
* an exact multiple of the number of zones, the right-most and bottom-most
* cells are ignored. The grid configuration is computed by
* IPAIPU3::calculateBdsGrid().
*
* Before calculating the gains, the algorithm aggregates the cell averages for
* each zone in generateAwbStats(). Cells that have a too high ratio of
* saturated pixels are ignored, and only zones that contain enough
* non-saturated cells are then used by the algorithm.
*
* The Grey World algorithm will then estimate the red and blue gains to apply, and
* store the results in the metadata. The green gain is always set to 1.
*/
Awb::Awb()
: Algorithm()
{
asyncResults_.blueGain = 1.0;
asyncResults_.greenGain = 1.0;
asyncResults_.redGain = 1.0;
asyncResults_.temperatureK = 4500;
zones_.reserve(kAwbStatsSizeX * kAwbStatsSizeY);
}
Awb::~Awb() = default;
int Awb::configure(IPAContext &context,
[[maybe_unused]] const IPAConfigInfo &configInfo)
{
const ipu3_uapi_grid_config &grid = context.configuration.grid.bdsGrid;
stride_ = context.configuration.grid.stride;
cellsPerZoneX_ = std::round(grid.width / static_cast<double>(kAwbStatsSizeX));
cellsPerZoneY_ = std::round(grid.height / static_cast<double>(kAwbStatsSizeY));
/*
* Configure the minimum proportion of cells counted within a zone
* for it to be relevant for the grey world algorithm.
* \todo This proportion could be configured.
*/
cellsPerZoneThreshold_ = cellsPerZoneX_ * cellsPerZoneY_ * kMaxCellSaturationRatio;
LOG(IPU3Awb, Debug) << "Threshold for AWB is set to " << cellsPerZoneThreshold_;
return 0;
}
/**
* The function estimates the correlated color temperature using
* from RGB color space input.
* In physics and color science, the Planckian locus or black body locus is
* the path or locus that the color of an incandescent black body would take
* in a particular chromaticity space as the blackbody temperature changes.
*
* If a narrow range of color temperatures is considered (those encapsulating
* daylight being the most practical case) one can approximate the Planckian
* locus in order to calculate the CCT in terms of chromaticity coordinates.
*
* More detailed information can be found in:
* https://en.wikipedia.org/wiki/Color_temperature#Approximation
*/
uint32_t Awb::estimateCCT(double red, double green, double blue)
{
/* Convert the RGB values to CIE tristimulus values (XYZ) */
double X = (-0.14282) * (red) + (1.54924) * (green) + (-0.95641) * (blue);
double Y = (-0.32466) * (red) + (1.57837) * (green) + (-0.73191) * (blue);
double Z = (-0.68202) * (red) + (0.77073) * (green) + (0.56332) * (blue);
/* Calculate the normalized chromaticity values */
double x = X / (X + Y + Z);
double y = Y / (X + Y + Z);
/* Calculate CCT */
double n = (x - 0.3320) / (0.1858 - y);
return 449 * n * n * n + 3525 * n * n + 6823.3 * n + 5520.33;
}
/* Generate an RGB vector with the average values for each zone */
void Awb::generateZones()
{
zones_.clear();
for (unsigned int i = 0; i < kAwbStatsSizeX * kAwbStatsSizeY; i++) {
RGB zone;
double counted = awbStats_[i].counted;
if (counted >= cellsPerZoneThreshold_) {
zone.G = awbStats_[i].sum.green / counted;
if (zone.G >= kMinGreenLevelInZone) {
zone.R = awbStats_[i].sum.red / counted;
zone.B = awbStats_[i].sum.blue / counted;
zones_.push_back(zone);
}
}
}
}
/* Translate the IPU3 statistics into the default statistics zone array */
void Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats)
{
/*
* Generate a (kAwbStatsSizeX x kAwbStatsSizeY) array from the IPU3 grid which is
* (grid.width x grid.height).
*/
for (unsigned int cellY = 0; cellY < kAwbStatsSizeY * cellsPerZoneY_; cellY++) {
for (unsigned int cellX = 0; cellX < kAwbStatsSizeX * cellsPerZoneX_; cellX++) {
uint32_t cellPosition = cellY * stride_ + cellX;
uint32_t zoneX = cellX / cellsPerZoneX_;
uint32_t zoneY = cellY / cellsPerZoneY_;
uint32_t awbZonePosition = zoneY * kAwbStatsSizeX + zoneX;
/* Cast the initial IPU3 structure to simplify the reading */
const ipu3_uapi_awb_set_item *currentCell =
reinterpret_cast<const ipu3_uapi_awb_set_item *>(
&stats->awb_raw_buffer.meta_data[cellPosition]
);
/*
* Use cells which have less than 90%
* saturation as an initial means to include
* otherwise bright cells which are not fully
* saturated.
*
* \todo The 90% saturation rate may require
* further empirical measurements and
* optimisation during camera tuning phases.
*/
if (currentCell->sat_ratio <= kMinCellsPerZoneRatio) {
/* The cell is not saturated, use the current cell */
awbStats_[awbZonePosition].counted++;
uint32_t greenValue = currentCell->Gr_avg + currentCell->Gb_avg;
awbStats_[awbZonePosition].sum.green += greenValue / 2;
awbStats_[awbZonePosition].sum.red += currentCell->R_avg;
awbStats_[awbZonePosition].sum.blue += currentCell->B_avg;
}
}
}
}
void Awb::clearAwbStats()
{
for (unsigned int i = 0; i < kAwbStatsSizeX * kAwbStatsSizeY; i++) {
awbStats_[i].sum.blue = 0;
awbStats_[i].sum.red = 0;
awbStats_[i].sum.green = 0;
awbStats_[i].counted = 0;
}
}
void Awb::awbGreyWorld()
{
LOG(IPU3Awb, Debug) << "Grey world AWB";
/*
* Make a separate list of the derivatives for each of red and blue, so
|
