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Diffstat (limited to 'third_party/jpeg-xl/lib/jxl/modular/transform/squeeze.h')
| -rw-r--r-- | third_party/jpeg-xl/lib/jxl/modular/transform/squeeze.h | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/third_party/jpeg-xl/lib/jxl/modular/transform/squeeze.h b/third_party/jpeg-xl/lib/jxl/modular/transform/squeeze.h new file mode 100644 index 0000000000..fb18710a6f --- /dev/null +++ b/third_party/jpeg-xl/lib/jxl/modular/transform/squeeze.h @@ -0,0 +1,90 @@ +// 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_MODULAR_TRANSFORM_SQUEEZE_H_ +#define LIB_JXL_MODULAR_TRANSFORM_SQUEEZE_H_ + +// Haar-like transform: halves the resolution in one direction +// A B -> (A+B)>>1 in one channel (average) -> same range as +// original channel +// A-B - tendency in a new channel ('residual' needed to make +// the transform reversible) +// -> theoretically range could be 2.5 +// times larger (2 times without the +// 'tendency'), but there should be lots +// of zeroes +// Repeated application (alternating horizontal and vertical squeezes) results +// in downscaling +// +// The default coefficient ordering is low-frequency to high-frequency, as in +// M. Antonini, M. Barlaud, P. Mathieu and I. Daubechies, "Image coding using +// wavelet transform", IEEE Transactions on Image Processing, vol. 1, no. 2, pp. +// 205-220, April 1992, doi: 10.1109/83.136597. + +#include <stdlib.h> + +#include "lib/jxl/base/data_parallel.h" +#include "lib/jxl/common.h" +#include "lib/jxl/modular/modular_image.h" +#include "lib/jxl/modular/transform/transform.h" + +#define JXL_MAX_FIRST_PREVIEW_SIZE 8 + +namespace jxl { + +/* + int avg=(A+B)>>1; + int diff=(A-B); + int rA=(diff+(avg<<1)+(diff&1))>>1; + int rB=rA-diff; + +*/ +// |A B|C D|E F| +// p a n p=avg(A,B), a=avg(C,D), n=avg(E,F) +// +// Goal: estimate C-D (avoiding ringing artifacts) +// (ensuring that in smooth areas, a zero residual corresponds to a smooth +// gradient) + +// best estimate for C: (B + 2*a)/3 +// best estimate for D: (n + 3*a)/4 +// best estimate for C-D: 4*B - 3*n - a /12 + +// avoid ringing by 1) only doing this if B <= a <= n or B >= a >= n +// (otherwise, this is not a smooth area and we cannot really estimate C-D) +// 2) making sure that B <= C <= D <= n or B >= C >= D >= n + +inline pixel_type_w SmoothTendency(pixel_type_w B, pixel_type_w a, + pixel_type_w n) { + pixel_type_w diff = 0; + if (B >= a && a >= n) { + diff = (4 * B - 3 * n - a + 6) / 12; + // 2C = a<<1 + diff - diff&1 <= 2B so diff - diff&1 <= 2B - 2a + // 2D = a<<1 - diff - diff&1 >= 2n so diff + diff&1 <= 2a - 2n + if (diff - (diff & 1) > 2 * (B - a)) diff = 2 * (B - a) + 1; + if (diff + (diff & 1) > 2 * (a - n)) diff = 2 * (a - n); + } else if (B <= a && a <= n) { + diff = (4 * B - 3 * n - a - 6) / 12; + // 2C = a<<1 + diff + diff&1 >= 2B so diff + diff&1 >= 2B - 2a + // 2D = a<<1 - diff + diff&1 <= 2n so diff - diff&1 >= 2a - 2n + if (diff + (diff & 1) < 2 * (B - a)) diff = 2 * (B - a) - 1; + if (diff - (diff & 1) < 2 * (a - n)) diff = 2 * (a - n); + } + return diff; +} + +void DefaultSqueezeParameters(std::vector<SqueezeParams> *parameters, + const Image &image); + +Status CheckMetaSqueezeParams(const SqueezeParams ¶meter, int num_channels); + +Status MetaSqueeze(Image &image, std::vector<SqueezeParams> *parameters); + +Status InvSqueeze(Image &input, std::vector<SqueezeParams> parameters, + ThreadPool *pool); + +} // namespace jxl + +#endif // LIB_JXL_MODULAR_TRANSFORM_SQUEEZE_H_ |