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Diffstat (limited to 'third_party/jpeg-xl/lib/jxl/dct_for_test.h')
-rw-r--r-- | third_party/jpeg-xl/lib/jxl/dct_for_test.h | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/dct_for_test.h b/third_party/jpeg-xl/lib/jxl/dct_for_test.h new file mode 100644 index 0000000000..58dd75e20e --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/dct_for_test.h @@ -0,0 +1,99 @@ +// 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(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(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(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_ |