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
|
// Copyright (c) the JPEG XL Project Authors. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#ifndef LIB_JXL_DCT_FOR_TEST_H_
#define LIB_JXL_DCT_FOR_TEST_H_
// Unoptimized DCT only for use in tests.
#include <string.h> // memcpy
#include <cmath>
#include <vector>
#include "lib/jxl/base/common.h"
namespace jxl {
namespace test {
static inline double alpha(int u) { return u == 0 ? 0.7071067811865475 : 1.0; }
// N-DCT on M columns, divided by sqrt(N). Matches the definition in the spec.
template <size_t N, size_t M>
void DCT1D(const double block[N * M], double out[N * M]) {
std::vector<double> matrix(N * N);
const double scale = std::sqrt(2.0) / N;
for (size_t y = 0; y < N; y++) {
for (size_t u = 0; u < N; u++) {
matrix[N * u + y] = alpha(u) * cos((y + 0.5) * u * Pi(1.0 / N)) * scale;
}
}
for (size_t x = 0; x < M; x++) {
for (size_t u = 0; u < N; u++) {
out[M * u + x] = 0;
for (size_t y = 0; y < N; y++) {
out[M * u + x] += matrix[N * u + y] * block[M * y + x];
}
}
}
}
// N-IDCT on M columns, multiplied by sqrt(N). Matches the definition in the
// spec.
template <size_t N, size_t M>
void IDCT1D(const double block[N * M], double out[N * M]) {
std::vector<double> matrix(N * N);
const double scale = std::sqrt(2.0);
for (size_t y = 0; y < N; y++) {
for (size_t u = 0; u < N; u++) {
// Transpose of DCT matrix.
matrix[N * y + u] = alpha(u) * cos((y + 0.5) * u * Pi(1.0 / N)) * scale;
}
}
for (size_t x = 0; x < M; x++) {
for (size_t u = 0; u < N; u++) {
out[M * u + x] = 0;
for (size_t y = 0; y < N; y++) {
out[M * u + x] += matrix[N * u + y] * block[M * y + x];
}
}
}
}
template <size_t N, size_t M>
void TransposeBlock(const double in[N * M], double out[M * N]) {
for (size_t x = 0; x < N; x++) {
for (size_t y = 0; y < M; y++) {
out[y * N + x] = in[x * M + y];
}
}
}
} // namespace test
// Untransposed DCT.
template <size_t N>
void DCTSlow(double block[N * N]) {
constexpr size_t kBlockSize = N * N;
std::vector<double> g(kBlockSize);
test::DCT1D<N, N>(block, g.data());
test::TransposeBlock<N, N>(g.data(), block);
test::DCT1D<N, N>(block, g.data());
test::TransposeBlock<N, N>(g.data(), block);
}
// Untransposed IDCT.
template <size_t N>
void IDCTSlow(double block[N * N]) {
constexpr size_t kBlockSize = N * N;
std::vector<double> g(kBlockSize);
test::IDCT1D<N, N>(block, g.data());
test::TransposeBlock<N, N>(g.data(), block);
test::IDCT1D<N, N>(block, g.data());
test::TransposeBlock<N, N>(g.data(), block);
}
} // namespace jxl
#endif // LIB_JXL_DCT_FOR_TEST_H_
|
