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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.
+
+// Edge-preserving smoothing: weighted average based on L1 patch similarity.
+
+#include "lib/jxl/epf.h"
+
+#include <math.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <algorithm>
+#include <atomic>
+#include <numeric> // std::accumulate
+#include <vector>
+
+#include "lib/jxl/ac_strategy.h"
+#include "lib/jxl/base/compiler_specific.h"
+#include "lib/jxl/base/data_parallel.h"
+#include "lib/jxl/base/status.h"
+#include "lib/jxl/convolve.h"
+#include "lib/jxl/dec_cache.h"
+#include "lib/jxl/image.h"
+#include "lib/jxl/image_bundle.h"
+#include "lib/jxl/image_ops.h"
+#include "lib/jxl/loop_filter.h"
+#include "lib/jxl/quant_weights.h"
+#include "lib/jxl/quantizer.h"
+
+namespace jxl {
+
+// Mirror n floats starting at *p and store them before p.
+JXL_INLINE void LeftMirror(float* p, size_t n) {
+ for (size_t i = 0; i < n; i++) {
+ *(p - 1 - i) = p[i];
+ }
+}
+
+// Mirror n floats starting at *(p - n) and store them at *p.
+JXL_INLINE void RightMirror(float* p, size_t n) {
+ for (size_t i = 0; i < n; i++) {
+ p[i] = *(p - 1 - i);
+ }
+}
+
+void ComputeSigma(const LoopFilter& lf, const Rect& block_rect,
+ PassesDecoderState* state) {
+ JXL_CHECK(lf.epf_iters > 0);
+ const AcStrategyImage& ac_strategy = state->shared->ac_strategy;
+ const float quant_scale = state->shared->quantizer.Scale();
+
+ const size_t sigma_stride = state->sigma.PixelsPerRow();
+ const size_t sharpness_stride = state->shared->epf_sharpness.PixelsPerRow();
+
+ for (size_t by = 0; by < block_rect.ysize(); ++by) {
+ float* JXL_RESTRICT sigma_row = block_rect.Row(&state->sigma, by);
+ const uint8_t* JXL_RESTRICT sharpness_row =
+ block_rect.ConstRow(state->shared->epf_sharpness, by);
+ AcStrategyRow acs_row = ac_strategy.ConstRow(block_rect, by);
+ const int32_t* const JXL_RESTRICT row_quant =
+ block_rect.ConstRow(state->shared->raw_quant_field, by);
+
+ for (size_t bx = 0; bx < block_rect.xsize(); bx++) {
+ AcStrategy acs = acs_row[bx];
+ size_t llf_x = acs.covered_blocks_x();
+ if (!acs.IsFirstBlock()) continue;
+ // quant_scale is smaller for low quality.
+ // quant_scale is roughly 0.08 / butteraugli score.
+ //
+ // row_quant is smaller for low quality.
+ // row_quant is a quantization multiplier of form 1.0 /
+ // row_quant[bx]
+ //
+ // lf.epf_quant_mul is a parameter in the format
+ // kInvSigmaNum is a constant
+ float sigma_quant =
+ lf.epf_quant_mul / (quant_scale * row_quant[bx] * kInvSigmaNum);
+ for (size_t iy = 0; iy < acs.covered_blocks_y(); iy++) {
+ for (size_t ix = 0; ix < acs.covered_blocks_x(); ix++) {
+ float sigma =
+ sigma_quant *
+ lf.epf_sharp_lut[sharpness_row[bx + ix + iy * sharpness_stride]];
+ // Avoid infinities.
+ sigma = std::min(-1e-4f, sigma); // TODO(veluca): remove this.
+ sigma_row[bx + ix + kSigmaPadding +
+ (iy + kSigmaPadding) * sigma_stride] = 1.0f / sigma;
+ }
+ }
+ // TODO(veluca): remove this padding.
+ // Left padding with mirroring.
+ if (bx + block_rect.x0() == 0) {
+ for (size_t iy = 0; iy < acs.covered_blocks_y(); iy++) {
+ LeftMirror(
+ sigma_row + kSigmaPadding + (iy + kSigmaPadding) * sigma_stride,
+ kSigmaBorder);
+ }
+ }
+ // Right padding with mirroring.
+ if (bx + block_rect.x0() + llf_x ==
+ state->shared->frame_dim.xsize_blocks) {
+ for (size_t iy = 0; iy < acs.covered_blocks_y(); iy++) {
+ RightMirror(sigma_row + kSigmaPadding + bx + llf_x +
+ (iy + kSigmaPadding) * sigma_stride,
+ kSigmaBorder);
+ }
+ }
+ // Offsets for row copying, in blocks.
+ size_t offset_before = bx + block_rect.x0() == 0 ? 1 : bx + kSigmaPadding;
+ size_t offset_after =
+ bx + block_rect.x0() + llf_x == state->shared->frame_dim.xsize_blocks
+ ? kSigmaPadding + llf_x + bx + kSigmaBorder
+ : kSigmaPadding + llf_x + bx;
+ size_t num = offset_after - offset_before;
+ // Above
+ if (by + block_rect.y0() == 0) {
+ for (size_t iy = 0; iy < kSigmaBorder; iy++) {
+ memcpy(
+ sigma_row + offset_before +
+ (kSigmaPadding - 1 - iy) * sigma_stride,
+ sigma_row + offset_before + (kSigmaPadding + iy) * sigma_stride,
+ num * sizeof(*sigma_row));
+ }
+ }
+ // Below
+ if (by + block_rect.y0() + acs.covered_blocks_y() ==
+ state->shared->frame_dim.ysize_blocks) {
+ for (size_t iy = 0; iy < kSigmaBorder; iy++) {
+ memcpy(
+ sigma_row + offset_before +
+ sigma_stride * (acs.covered_blocks_y() + kSigmaPadding + iy),
+ sigma_row + offset_before +
+ sigma_stride *
+ (acs.covered_blocks_y() + kSigmaPadding - 1 - iy),
+ num * sizeof(*sigma_row));
+ }
+ }
+ }
+ }
+}
+
+} // namespace jxl