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Alpha coding: reorganize the filter/unfiltering code

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Move the filtering code to their own dsp/ spot
New function: VP8FiltersInit()

Change-Id: I0b2041eab42346c59b972f2575b05509e6a8f7b1
This commit is contained in:
Pascal Massimino
2015-01-28 08:02:41 +01:00
parent ec0d1be577
commit 7afdaf8496
12 changed files with 291 additions and 233 deletions
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206
src/utils/filters.c
View File

@ -7,200 +7,27 @@
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Spatial prediction using various filters
// filter estimation
//
// Author: Urvang (urvang@google.com)
#include "./filters.h"
#include <assert.h>
#include <stdlib.h>
#include <string.h>
//------------------------------------------------------------------------------
// Helpful macro.
# define SANITY_CHECK(in, out) \
assert(in != NULL); \
assert(out != NULL); \
assert(width > 0); \
assert(height > 0); \
assert(stride >= width); \
assert(row >= 0 && num_rows > 0 && row + num_rows <= height); \
(void)height; // Silence unused warning.
static WEBP_INLINE void PredictLine(const uint8_t* src, const uint8_t* pred,
uint8_t* dst, int length, int inverse) {
int i;
if (inverse) {
for (i = 0; i < length; ++i) dst[i] = src[i] + pred[i];
} else {
for (i = 0; i < length; ++i) dst[i] = src[i] - pred[i];
}
}
//------------------------------------------------------------------------------
// Horizontal filter.
static WEBP_INLINE void DoHorizontalFilter(const uint8_t* in,
int width, int height, int stride,
int row, int num_rows,
int inverse, uint8_t* out) {
const uint8_t* preds;
const size_t start_offset = row * stride;
const int last_row = row + num_rows;
SANITY_CHECK(in, out);
in += start_offset;
out += start_offset;
preds = inverse ? out : in;
if (row == 0) {
// Leftmost pixel is the same as input for topmost scanline.
out[0] = in[0];
PredictLine(in + 1, preds, out + 1, width - 1, inverse);
row = 1;
preds += stride;
in += stride;
out += stride;
}
// Filter line-by-line.
while (row < last_row) {
// Leftmost pixel is predicted from above.
PredictLine(in, preds - stride, out, 1, inverse);
PredictLine(in + 1, preds, out + 1, width - 1, inverse);
++row;
preds += stride;
in += stride;
out += stride;
}
}
static void HorizontalFilter(const uint8_t* data, int width, int height,
int stride, uint8_t* filtered_data) {
DoHorizontalFilter(data, width, height, stride, 0, height, 0, filtered_data);
}
static void HorizontalUnfilter(int width, int height, int stride, int row,
int num_rows, uint8_t* data) {
DoHorizontalFilter(data, width, height, stride, row, num_rows, 1, data);
}
//------------------------------------------------------------------------------
// Vertical filter.
static WEBP_INLINE void DoVerticalFilter(const uint8_t* in,
int width, int height, int stride,
int row, int num_rows,
int inverse, uint8_t* out) {
const uint8_t* preds;
const size_t start_offset = row * stride;
const int last_row = row + num_rows;
SANITY_CHECK(in, out);
in += start_offset;
out += start_offset;
preds = inverse ? out : in;
if (row == 0) {
// Very first top-left pixel is copied.
out[0] = in[0];
// Rest of top scan-line is left-predicted.
PredictLine(in + 1, preds, out + 1, width - 1, inverse);
row = 1;
in += stride;
out += stride;
} else {
// We are starting from in-between. Make sure 'preds' points to prev row.
preds -= stride;
}
// Filter line-by-line.
while (row < last_row) {
PredictLine(in, preds, out, width, inverse);
++row;
preds += stride;
in += stride;
out += stride;
}
}
static void VerticalFilter(const uint8_t* data, int width, int height,
int stride, uint8_t* filtered_data) {
DoVerticalFilter(data, width, height, stride, 0, height, 0, filtered_data);
}
static void VerticalUnfilter(int width, int height, int stride, int row,
int num_rows, uint8_t* data) {
DoVerticalFilter(data, width, height, stride, row, num_rows, 1, data);
}
//------------------------------------------------------------------------------
// Gradient filter.
static WEBP_INLINE int GradientPredictor(uint8_t a, uint8_t b, uint8_t c) {
const int g = a + b - c;
return ((g & ~0xff) == 0) ? g : (g < 0) ? 0 : 255; // clip to 8bit
}
static WEBP_INLINE void DoGradientFilter(const uint8_t* in,
int width, int height, int stride,
int row, int num_rows,
int inverse, uint8_t* out) {
const uint8_t* preds;
const size_t start_offset = row * stride;
const int last_row = row + num_rows;
SANITY_CHECK(in, out);
in += start_offset;
out += start_offset;
preds = inverse ? out : in;
// left prediction for top scan-line
if (row == 0) {
out[0] = in[0];
PredictLine(in + 1, preds, out + 1, width - 1, inverse);
row = 1;
preds += stride;
in += stride;
out += stride;
}
// Filter line-by-line.
while (row < last_row) {
int w;
// leftmost pixel: predict from above.
PredictLine(in, preds - stride, out, 1, inverse);
for (w = 1; w < width; ++w) {
const int pred = GradientPredictor(preds[w - 1],
preds[w - stride],
preds[w - stride - 1]);
out[w] = in[w] + (inverse ? pred : -pred);
}
++row;
preds += stride;
in += stride;
out += stride;
}
}
static void GradientFilter(const uint8_t* data, int width, int height,
int stride, uint8_t* filtered_data) {
DoGradientFilter(data, width, height, stride, 0, height, 0, filtered_data);
}
static void GradientUnfilter(int width, int height, int stride, int row,
int num_rows, uint8_t* data) {
DoGradientFilter(data, width, height, stride, row, num_rows, 1, data);
}
#undef SANITY_CHECK
// -----------------------------------------------------------------------------
// Quick estimate of a potentially interesting filter mode to try.
#define SMAX 16
#define SDIFF(a, b) (abs((a) - (b)) >> 4) // Scoring diff, in [0..SMAX)
WEBP_FILTER_TYPE EstimateBestFilter(const uint8_t* data,
int width, int height, int stride) {
static WEBP_INLINE int GradientPredictor(uint8_t a, uint8_t b, uint8_t c) {
const int g = a + b - c;
return ((g & ~0xff) == 0) ? g : (g < 0) ? 0 : 255; // clip to 8bit
}
WEBP_FILTER_TYPE WebPEstimateBestFilter(const uint8_t* data,
int width, int height, int stride) {
int i, j;
int bins[WEBP_FILTER_LAST][SMAX];
memset(bins, 0, sizeof(bins));
@ -247,20 +74,3 @@ WEBP_FILTER_TYPE EstimateBestFilter(const uint8_t* data,
#undef SDIFF
//------------------------------------------------------------------------------
WebPFilterFunc WebPFilters[WEBP_FILTER_LAST] = {
NULL, // WEBP_FILTER_NONE
HorizontalFilter, // WEBP_FILTER_HORIZONTAL
VerticalFilter, // WEBP_FILTER_VERTICAL
GradientFilter // WEBP_FILTER_GRADIENT
};
WebPUnfilterFunc WebPUnfilters[WEBP_FILTER_LAST] = {
NULL, // WEBP_FILTER_NONE
HorizontalUnfilter, // WEBP_FILTER_HORIZONTAL
VerticalUnfilter, // WEBP_FILTER_VERTICAL
GradientUnfilter // WEBP_FILTER_GRADIENT
};
//------------------------------------------------------------------------------

33
src/utils/filters.h
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@ -15,42 +15,15 @@
#define WEBP_UTILS_FILTERS_H_
#include "../webp/types.h"
#include "../dsp/dsp.h"
#ifdef __cplusplus
extern "C" {
#endif
// Filters.
typedef enum {
WEBP_FILTER_NONE = 0,
WEBP_FILTER_HORIZONTAL,
WEBP_FILTER_VERTICAL,
WEBP_FILTER_GRADIENT,
WEBP_FILTER_LAST = WEBP_FILTER_GRADIENT + 1, // end marker
WEBP_FILTER_BEST,
WEBP_FILTER_FAST
} WEBP_FILTER_TYPE;
typedef void (*WebPFilterFunc)(const uint8_t* in, int width, int height,
int stride, uint8_t* out);
typedef void (*WebPUnfilterFunc)(int width, int height, int stride,
int row, int num_rows, uint8_t* data);
// Filter the given data using the given predictor.
// 'in' corresponds to a 2-dimensional pixel array of size (stride * height)
// in raster order.
// 'stride' is number of bytes per scan line (with possible padding).
// 'out' should be pre-allocated.
extern WebPFilterFunc WebPFilters[WEBP_FILTER_LAST];
// In-place reconstruct the original data from the given filtered data.
// The reconstruction will be done for 'num_rows' rows starting from 'row'
// (assuming rows upto 'row - 1' are already reconstructed).
extern WebPUnfilterFunc WebPUnfilters[WEBP_FILTER_LAST];
// Fast estimate of a potentially good filter.
WEBP_FILTER_TYPE EstimateBestFilter(const uint8_t* data,
int width, int height, int stride);
WEBP_FILTER_TYPE WebPEstimateBestFilter(const uint8_t* data,
int width, int height, int stride);
#ifdef __cplusplus
} // extern "C"