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
|
#include "exif_parser.h"
#include <movit/colorspace_conversion_effect.h>
#include <stdint.h>
#include <Eigen/Core>
#include <Eigen/LU>
using namespace Eigen;
using namespace movit;
using namespace std;
uint32_t read32be(const uint8_t *data)
{
return (uint32_t(data[0]) << 24) |
(uint32_t(data[1]) << 16) |
(uint32_t(data[2]) << 8) |
uint32_t(data[3]);
}
uint16_t read16be(const uint8_t *data)
{
return (uint16_t(data[0]) << 8) | uint16_t(data[1]);
}
RGBTriplet get_neutral_color(const string &exif)
{
if (exif.empty()) {
return {1.0f, 1.0f, 1.0f};
}
const uint8_t *data = reinterpret_cast<const uint8_t *>(exif.data());
// Very rudimentary Exif parser (and probably integer-overflowable);
// we really only care about what Nageru sends us (MJPEGEncoder::init_jpeg_422()),
// but it would be nice to have a little bit of future-proofing, just in case.
if (exif.size() < 14 || memcmp(data, "Exif\0\0MM\0\x2a", 10) != 0) {
fprintf(stderr, "WARNING: Truncated or malformed Exif header, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
// We only care about the first IFD.
uint32_t ifd_offset = read32be(data + 10);
ifd_offset += 6; // Relative to the MM.
if (ifd_offset < 14 || ifd_offset >= exif.size()) {
fprintf(stderr, "WARNING: Truncated or malformed Exif IFD, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
// Skip over number of tags (16 bits); if the white point is not the first one,
// we're bailing anyway.
if (ifd_offset + 2 > exif.size() || ifd_offset + 2 < ifd_offset) {
fprintf(stderr, "WARNING: Exif IFD has no rom for number of tags, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
if (ifd_offset + 4 > exif.size() || ifd_offset + 4 < ifd_offset) {
fprintf(stderr, "WARNING: Exif IFD has no rom for tag, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
uint16_t tag = read16be(data + ifd_offset + 2);
if (tag != 0x13e) { // WhitePoint.
fprintf(stderr, "WARNING: Unexpected first Exif tag, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
if (ifd_offset + 14 > exif.size() || ifd_offset + 14 < ifd_offset) {
fprintf(stderr, "WARNING: WhitePoint Exif tag was truncated, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
// Just assume we're rational type and two values...
uint32_t white_point_offset = read32be(data + ifd_offset + 10);
white_point_offset += 6; // Relative to the MM.
if (white_point_offset >= exif.size()) {
fprintf(stderr, "WARNING: WhitePoint Exif tag was out of bounds, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
if (white_point_offset + 16 > exif.size()) {
fprintf(stderr, "WARNING: WhitePoint Exif tag was truncated, ignoring.\n");
return {1.0f, 1.0f, 1.0f};
}
uint32_t x_nom = read32be(data + white_point_offset);
uint32_t x_den = read32be(data + white_point_offset + 4);
uint32_t y_nom = read32be(data + white_point_offset + 8);
uint32_t y_den = read32be(data + white_point_offset + 12);
double x = double(x_nom) / x_den;
double y = double(y_nom) / y_den;
double z = 1.0 - x - y;
Matrix3d rgb_to_xyz_matrix = movit::ColorspaceConversionEffect::get_xyz_matrix(COLORSPACE_sRGB);
Vector3d rgb = rgb_to_xyz_matrix.inverse() * Vector3d(x, y, z);
return RGBTriplet(rgb[0], rgb[1], rgb[2]);
}
|
