mirror of
https://github.com/webmproject/libwebp.git
synced 2025-07-14 21:09:55 +02:00
move the rescaling code into its own file and make enc/ and dec/ use it.
(cherry picked from commit 8e92d9e380a89b7443a2e2c3d16ce5a222e8c1e8) Conflicts: Android.mk makefile.unix src/dec/vp8l.c src/utils/Makefile.am
This commit is contained in:
Pascal Massimino
committed by
James Zern
James Zern
parent
efc2016a31
commit
61c2d51fd7
@ -4,7 +4,7 @@ libwebputils_la_SOURCES = alpha.h alpha.c \
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bit_reader.h bit_reader.c \
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bit_writer.h bit_writer.c \
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filters.h filters.c \
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quant_levels.c \
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quant_levels.c rescaler.c \
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tcoder.h tcoderi.h tcoder.c \
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thread.h thread.c
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libwebputilsinclude_HEADERS = ../webp/types.h
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152
src/utils/rescaler.c
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152
src/utils/rescaler.c
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// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Rescaling functions
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//
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// Author: Skal (pascal.massimino@gmail.com)
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#include <assert.h>
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#include <stdlib.h>
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#include "./rescaler.h"
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//------------------------------------------------------------------------------
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#define RFIX 30
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#define MULT_FIX(x,y) (((int64_t)(x) * (y) + (1 << (RFIX - 1))) >> RFIX)
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void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
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uint8_t* const dst, int dst_width, int dst_height,
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int dst_stride, int num_channels, int x_add, int x_sub,
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int y_add, int y_sub, int32_t* const work) {
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wrk->x_expand = (src_width < dst_width);
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wrk->src_width = src_width;
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wrk->src_height = src_height;
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wrk->dst_width = dst_width;
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wrk->dst_height = dst_height;
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wrk->dst = dst;
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wrk->dst_stride = dst_stride;
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wrk->num_channels = num_channels;
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// for 'x_expand', we use bilinear interpolation
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wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add - x_sub;
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wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub;
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wrk->y_accum = y_add;
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wrk->y_add = y_add;
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wrk->y_sub = y_sub;
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wrk->fx_scale = (1 << RFIX) / x_sub;
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wrk->fy_scale = (1 << RFIX) / y_sub;
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wrk->fxy_scale = wrk->x_expand ?
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((int64_t)dst_height << RFIX) / (x_sub * src_height) :
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((int64_t)dst_height << RFIX) / (x_add * src_height);
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wrk->irow = work;
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wrk->frow = work + num_channels * dst_width;
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}
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void WebPRescalerImportRow(WebPRescaler* const wrk,
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const uint8_t* const src, int channel) {
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const int x_stride = wrk->num_channels;
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const int x_out_max = wrk->dst_width * wrk->num_channels;
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int x_in = channel;
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int x_out;
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int accum = 0;
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if (!wrk->x_expand) {
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int sum = 0;
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for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
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accum += wrk->x_add;
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for (; accum > 0; accum -= wrk->x_sub) {
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sum += src[x_in];
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x_in += x_stride;
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}
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{ // Emit next horizontal pixel.
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const int32_t base = src[x_in];
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const int32_t frac = base * (-accum);
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x_in += x_stride;
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wrk->frow[x_out] = (sum + base) * wrk->x_sub - frac;
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// fresh fractional start for next pixel
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sum = (int)MULT_FIX(frac, wrk->fx_scale);
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}
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}
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} else { // simple bilinear interpolation
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int left = src[channel], right = src[channel];
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for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
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if (accum < 0) {
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left = right;
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x_in += x_stride;
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right = src[x_in];
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accum += wrk->x_add;
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}
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wrk->frow[x_out] = right * wrk->x_add + (left - right) * accum;
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accum -= wrk->x_sub;
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}
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}
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// Accumulate the new row's contribution
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for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
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wrk->irow[x_out] += wrk->frow[x_out];
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}
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}
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uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk) {
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if (wrk->y_accum <= 0) {
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int x_out;
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uint8_t* const dst = wrk->dst;
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int32_t* const irow = wrk->irow;
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const int32_t* const frow = wrk->frow;
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const int yscale = wrk->fy_scale * (-wrk->y_accum);
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const int x_out_max = wrk->dst_width * wrk->num_channels;
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for (x_out = 0; x_out < x_out_max; ++x_out) {
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const int frac = (int)MULT_FIX(frow[x_out], yscale);
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const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
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dst[x_out] = (!(v & ~0xff)) ? v : (v < 0) ? 0 : 255;
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irow[x_out] = frac; // new fractional start
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}
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wrk->y_accum += wrk->y_add;
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wrk->dst += wrk->dst_stride;
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return dst;
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} else {
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return NULL;
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}
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}
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#undef MULT_FIX
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#undef RFIX
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//------------------------------------------------------------------------------
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// all-in-one calls
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int WebPRescalerImport(WebPRescaler* const wrk, int num_lines,
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const uint8_t* src, int src_stride) {
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int total_imported = 0;
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while (total_imported < num_lines && wrk->y_accum > 0) {
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int channel;
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for (channel = 0; channel < wrk->num_channels; ++channel) {
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WebPRescalerImportRow(wrk, src, channel);
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}
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src += src_stride;
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++total_imported;
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wrk->y_accum -= wrk->y_sub;
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}
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return total_imported;
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}
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int WebPRescalerExport(WebPRescaler* const rescaler) {
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int total_exported = 0;
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while (WebPRescalerHasPendingOutput(rescaler)) {
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WebPRescalerExportRow(rescaler);
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++total_exported;
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}
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return total_exported;
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}
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//------------------------------------------------------------------------------
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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76
src/utils/rescaler.h
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76
src/utils/rescaler.h
Normal file
@ -0,0 +1,76 @@
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// Copyright 2012 Google Inc. All Rights Reserved.
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//
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// This code is licensed under the same terms as WebM:
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// Software License Agreement: http://www.webmproject.org/license/software/
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// Additional IP Rights Grant: http://www.webmproject.org/license/additional/
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// -----------------------------------------------------------------------------
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//
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// Rescaling functions
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//
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// Author: skal@google.com (Pascal Massimino)
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#ifndef WEBP_UTILS_RESCALER_H_
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#define WEBP_UTILS_RESCALER_H_
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#include "../webp/types.h"
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// Structure used for on-the-fly rescaling
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typedef struct {
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int x_expand; // true if we're expanding in the x direction
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int num_channels; // bytes to jump between pixels
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int fy_scale, fx_scale; // fixed-point scaling factor
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int64_t fxy_scale; // ''
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// we need hpel-precise add/sub increments, for the downsampled U/V planes.
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int y_accum; // vertical accumulator
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int y_add, y_sub; // vertical increments (add ~= src, sub ~= dst)
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int x_add, x_sub; // horizontal increments (add ~= src, sub ~= dst)
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int src_width, src_height; // source dimensions
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int dst_width, dst_height; // destination dimensions
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uint8_t* dst;
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int dst_stride;
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int32_t* irow, *frow; // work buffer
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} WebPRescaler;
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// Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
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void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
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uint8_t* const dst,
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int dst_width, int dst_height, int dst_stride,
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int num_channels,
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int x_add, int x_sub,
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int y_add, int y_sub,
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int32_t* const work);
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// Import a row of data and save its contribution in the rescaler.
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// 'channel' denotes the channel number to be imported.
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void WebPRescalerImportRow(WebPRescaler* const rescaler,
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const uint8_t* const src, int channel);
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// Import multiple rows over all channels, until at least one row is ready to
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// be exported. Returns the actual number of lines that were imported.
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int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
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const uint8_t* src, int src_stride);
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// Return true if there is pending output rows ready.
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static WEBP_INLINE
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int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
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return (rescaler->y_accum <= 0);
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}
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// Export one row from rescaler. Returns the pointer where output was written,
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// or NULL if no row was pending.
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uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk);
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// Export as many rows as possible. Return the numbers of rows written.
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int WebPRescalerExport(WebPRescaler* const wrk);
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//------------------------------------------------------------------------------
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#if defined(__cplusplus) || defined(c_plusplus)
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} // extern "C"
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#endif
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#endif /* WEBP_UTILS_RESCALER_H_ */
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