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-rw-r--r--thirdparty/libwebp/src/utils/quant_levels_dec_utils.c285
1 files changed, 285 insertions, 0 deletions
diff --git a/thirdparty/libwebp/src/utils/quant_levels_dec_utils.c b/thirdparty/libwebp/src/utils/quant_levels_dec_utils.c
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+++ b/thirdparty/libwebp/src/utils/quant_levels_dec_utils.c
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+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// Implement gradient smoothing: we replace a current alpha value by its
+// surrounding average if it's close enough (that is: the change will be less
+// than the minimum distance between two quantized level).
+// We use sliding window for computing the 2d moving average.
+//
+// Author: Skal (pascal.massimino@gmail.com)
+
+#include "src/utils/quant_levels_dec_utils.h"
+
+#include <string.h> // for memset
+
+#include "src/utils/utils.h"
+
+// #define USE_DITHERING // uncomment to enable ordered dithering (not vital)
+
+#define FIX 16 // fix-point precision for averaging
+#define LFIX 2 // extra precision for look-up table
+#define LUT_SIZE ((1 << (8 + LFIX)) - 1) // look-up table size
+
+#if defined(USE_DITHERING)
+
+#define DFIX 4 // extra precision for ordered dithering
+#define DSIZE 4 // dithering size (must be a power of two)
+// cf. http://en.wikipedia.org/wiki/Ordered_dithering
+static const uint8_t kOrderedDither[DSIZE][DSIZE] = {
+ { 0, 8, 2, 10 }, // coefficients are in DFIX fixed-point precision
+ { 12, 4, 14, 6 },
+ { 3, 11, 1, 9 },
+ { 15, 7, 13, 5 }
+};
+
+#else
+#define DFIX 0
+#endif
+
+typedef struct {
+ int width_, height_; // dimension
+ int stride_; // stride in bytes
+ int row_; // current input row being processed
+ uint8_t* src_; // input pointer
+ uint8_t* dst_; // output pointer
+
+ int radius_; // filter radius (=delay)
+ int scale_; // normalization factor, in FIX bits precision
+
+ void* mem_; // all memory
+
+ // various scratch buffers
+ uint16_t* start_;
+ uint16_t* cur_;
+ uint16_t* end_;
+ uint16_t* top_;
+ uint16_t* average_;
+
+ // input levels distribution
+ int num_levels_; // number of quantized levels
+ int min_, max_; // min and max level values
+ int min_level_dist_; // smallest distance between two consecutive levels
+
+ int16_t* correction_; // size = 1 + 2*LUT_SIZE -> ~4k memory
+} SmoothParams;
+
+//------------------------------------------------------------------------------
+
+#define CLIP_8b_MASK (int)(~0U << (8 + DFIX))
+static WEBP_INLINE uint8_t clip_8b(int v) {
+ return (!(v & CLIP_8b_MASK)) ? (uint8_t)(v >> DFIX) : (v < 0) ? 0u : 255u;
+}
+#undef CLIP_8b_MASK
+
+// vertical accumulation
+static void VFilter(SmoothParams* const p) {
+ const uint8_t* src = p->src_;
+ const int w = p->width_;
+ uint16_t* const cur = p->cur_;
+ const uint16_t* const top = p->top_;
+ uint16_t* const out = p->end_;
+ uint16_t sum = 0; // all arithmetic is modulo 16bit
+ int x;
+
+ for (x = 0; x < w; ++x) {
+ uint16_t new_value;
+ sum += src[x];
+ new_value = top[x] + sum;
+ out[x] = new_value - cur[x]; // vertical sum of 'r' pixels.
+ cur[x] = new_value;
+ }
+ // move input pointers one row down
+ p->top_ = p->cur_;
+ p->cur_ += w;
+ if (p->cur_ == p->end_) p->cur_ = p->start_; // roll-over
+ // We replicate edges, as it's somewhat easier as a boundary condition.
+ // That's why we don't update the 'src' pointer on top/bottom area:
+ if (p->row_ >= 0 && p->row_ < p->height_ - 1) {
+ p->src_ += p->stride_;
+ }
+}
+
+// horizontal accumulation. We use mirror replication of missing pixels, as it's
+// a little easier to implement (surprisingly).
+static void HFilter(SmoothParams* const p) {
+ const uint16_t* const in = p->end_;
+ uint16_t* const out = p->average_;
+ const uint32_t scale = p->scale_;
+ const int w = p->width_;
+ const int r = p->radius_;
+
+ int x;
+ for (x = 0; x <= r; ++x) { // left mirroring
+ const uint16_t delta = in[x + r - 1] + in[r - x];
+ out[x] = (delta * scale) >> FIX;
+ }
+ for (; x < w - r; ++x) { // bulk middle run
+ const uint16_t delta = in[x + r] - in[x - r - 1];
+ out[x] = (delta * scale) >> FIX;
+ }
+ for (; x < w; ++x) { // right mirroring
+ const uint16_t delta =
+ 2 * in[w - 1] - in[2 * w - 2 - r - x] - in[x - r - 1];
+ out[x] = (delta * scale) >> FIX;
+ }
+}
+
+// emit one filtered output row
+static void ApplyFilter(SmoothParams* const p) {
+ const uint16_t* const average = p->average_;
+ const int w = p->width_;
+ const int16_t* const correction = p->correction_;
+#if defined(USE_DITHERING)
+ const uint8_t* const dither = kOrderedDither[p->row_ % DSIZE];
+#endif
+ uint8_t* const dst = p->dst_;
+ int x;
+ for (x = 0; x < w; ++x) {
+ const int v = dst[x];
+ if (v < p->max_ && v > p->min_) {
+ const int c = (v << DFIX) + correction[average[x] - (v << LFIX)];
+#if defined(USE_DITHERING)
+ dst[x] = clip_8b(c + dither[x % DSIZE]);
+#else
+ dst[x] = clip_8b(c);
+#endif
+ }
+ }
+ p->dst_ += p->stride_; // advance output pointer
+}
+
+//------------------------------------------------------------------------------
+// Initialize correction table
+
+static void InitCorrectionLUT(int16_t* const lut, int min_dist) {
+ // The correction curve is:
+ // f(x) = x for x <= threshold2
+ // f(x) = 0 for x >= threshold1
+ // and a linear interpolation for range x=[threshold2, threshold1]
+ // (along with f(-x) = -f(x) symmetry).
+ // Note that: threshold2 = 3/4 * threshold1
+ const int threshold1 = min_dist << LFIX;
+ const int threshold2 = (3 * threshold1) >> 2;
+ const int max_threshold = threshold2 << DFIX;
+ const int delta = threshold1 - threshold2;
+ int i;
+ for (i = 1; i <= LUT_SIZE; ++i) {
+ int c = (i <= threshold2) ? (i << DFIX)
+ : (i < threshold1) ? max_threshold * (threshold1 - i) / delta
+ : 0;
+ c >>= LFIX;
+ lut[+i] = +c;
+ lut[-i] = -c;
+ }
+ lut[0] = 0;
+}
+
+static void CountLevels(SmoothParams* const p) {
+ int i, j, last_level;
+ uint8_t used_levels[256] = { 0 };
+ const uint8_t* data = p->src_;
+ p->min_ = 255;
+ p->max_ = 0;
+ for (j = 0; j < p->height_; ++j) {
+ for (i = 0; i < p->width_; ++i) {
+ const int v = data[i];
+ if (v < p->min_) p->min_ = v;
+ if (v > p->max_) p->max_ = v;
+ used_levels[v] = 1;
+ }
+ data += p->stride_;
+ }
+ // Compute the mininum distance between two non-zero levels.
+ p->min_level_dist_ = p->max_ - p->min_;
+ last_level = -1;
+ for (i = 0; i < 256; ++i) {
+ if (used_levels[i]) {
+ ++p->num_levels_;
+ if (last_level >= 0) {
+ const int level_dist = i - last_level;
+ if (level_dist < p->min_level_dist_) {
+ p->min_level_dist_ = level_dist;
+ }
+ }
+ last_level = i;
+ }
+ }
+}
+
+// Initialize all params.
+static int InitParams(uint8_t* const data, int width, int height, int stride,
+ int radius, SmoothParams* const p) {
+ const int R = 2 * radius + 1; // total size of the kernel
+
+ const size_t size_scratch_m = (R + 1) * width * sizeof(*p->start_);
+ const size_t size_m = width * sizeof(*p->average_);
+ const size_t size_lut = (1 + 2 * LUT_SIZE) * sizeof(*p->correction_);
+ const size_t total_size = size_scratch_m + size_m + size_lut;
+ uint8_t* mem = (uint8_t*)WebPSafeMalloc(1U, total_size);
+
+ if (mem == NULL) return 0;
+ p->mem_ = (void*)mem;
+
+ p->start_ = (uint16_t*)mem;
+ p->cur_ = p->start_;
+ p->end_ = p->start_ + R * width;
+ p->top_ = p->end_ - width;
+ memset(p->top_, 0, width * sizeof(*p->top_));
+ mem += size_scratch_m;
+
+ p->average_ = (uint16_t*)mem;
+ mem += size_m;
+
+ p->width_ = width;
+ p->height_ = height;
+ p->stride_ = stride;
+ p->src_ = data;
+ p->dst_ = data;
+ p->radius_ = radius;
+ p->scale_ = (1 << (FIX + LFIX)) / (R * R); // normalization constant
+ p->row_ = -radius;
+
+ // analyze the input distribution so we can best-fit the threshold
+ CountLevels(p);
+
+ // correction table
+ p->correction_ = ((int16_t*)mem) + LUT_SIZE;
+ InitCorrectionLUT(p->correction_, p->min_level_dist_);
+
+ return 1;
+}
+
+static void CleanupParams(SmoothParams* const p) {
+ WebPSafeFree(p->mem_);
+}
+
+int WebPDequantizeLevels(uint8_t* const data, int width, int height, int stride,
+ int strength) {
+ const int radius = 4 * strength / 100;
+ if (strength < 0 || strength > 100) return 0;
+ if (data == NULL || width <= 0 || height <= 0) return 0; // bad params
+ if (radius > 0) {
+ SmoothParams p;
+ memset(&p, 0, sizeof(p));
+ if (!InitParams(data, width, height, stride, radius, &p)) return 0;
+ if (p.num_levels_ > 2) {
+ for (; p.row_ < p.height_; ++p.row_) {
+ VFilter(&p); // accumulate average of input
+ // Need to wait few rows in order to prime the filter,
+ // before emitting some output.
+ if (p.row_ >= p.radius_) {
+ HFilter(&p);
+ ApplyFilter(&p);
+ }
+ }
+ }
+ CleanupParams(&p);
+ }
+ return 1;
+}
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