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// 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.
#include "lib/jxl/enc_gaborish.h"
#include <stddef.h>
#include <hwy/base.h>
#include "lib/jxl/base/status.h"
#include "lib/jxl/convolve.h"
#include "lib/jxl/image_ops.h"
namespace jxl {
void GaborishInverse(Image3F* in_out, float mul[3], ThreadPool* pool) {
WeightsSymmetric5 weights[3];
// Only an approximation. One or even two 3x3, and rank-1 (separable) 5x5
// are insufficient. The numbers here have been obtained by butteraugli
// based optimizing the whole system and the errors produced are likely
// more favorable for good rate-distortion compromises rather than
// just using mathematical optimization to find the inverse.
static const float kGaborish[5] = {
-0.090881924078487886f, -0.043663953593472138f, 0.01392497846646211f,
0.0036189602184591141f, 0.0030557936884763499f};
for (int i = 0; i < 3; ++i) {
double sum = 1.0 + mul[i] * 4 *
(kGaborish[0] + kGaborish[1] + kGaborish[2] +
kGaborish[4] + 2 * kGaborish[3]);
if (sum < 1e-5) {
sum = 1e-5;
}
const float normalize = static_cast<float>(1.0 / sum);
const float normalize_mul = mul[i] * normalize;
weights[i] = WeightsSymmetric5{{HWY_REP4(normalize)},
{HWY_REP4(normalize_mul * kGaborish[0])},
{HWY_REP4(normalize_mul * kGaborish[2])},
{HWY_REP4(normalize_mul * kGaborish[1])},
{HWY_REP4(normalize_mul * kGaborish[4])},
{HWY_REP4(normalize_mul * kGaborish[3])}};
}
// Reduce memory footprint by only allocating a single plane and swapping it
// into the output Image3F. Better still would be tiling.
// Note that we cannot *allocate* a plane, as doing so might cause Image3F to
// have planes of different stride. Instead, we copy one plane in a temporary
// image and reuse the existing planes of the in/out image.
ImageF temp = CopyImage(in_out->Plane(2));
Symmetric5(in_out->Plane(0), Rect(*in_out), weights[0], pool,
&in_out->Plane(2));
Symmetric5(in_out->Plane(1), Rect(*in_out), weights[1], pool,
&in_out->Plane(0));
Symmetric5(temp, Rect(*in_out), weights[2], pool, &in_out->Plane(1));
// Now planes are 1, 2, 0.
in_out->Plane(0).Swap(in_out->Plane(1));
// 2 1 0
in_out->Plane(0).Swap(in_out->Plane(2));
}
} // namespace jxl
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