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// Copyright 2012 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.
// -----------------------------------------------------------------------------
//
// Rescaling functions
//
// Author: Skal (pascal.massimino@gmail.com)
#include <assert.h>
#include <stdlib.h>
#include "./rescaler.h"
//------------------------------------------------------------------------------
#define RFIX 30
#define MULT_FIX(x, y) (((int64_t)(x) * (y) + (1 << (RFIX - 1))) >> RFIX)
void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height,
uint8_t* const dst, int dst_width, int dst_height,
int dst_stride, int num_channels, int x_add, int x_sub,
int y_add, int y_sub, int32_t* const work) {
wrk->x_expand = (src_width < dst_width);
wrk->src_width = src_width;
wrk->src_height = src_height;
wrk->dst_width = dst_width;
wrk->dst_height = dst_height;
wrk->dst = dst;
wrk->dst_stride = dst_stride;
wrk->num_channels = num_channels;
// for 'x_expand', we use bilinear interpolation
wrk->x_add = wrk->x_expand ? (x_sub - 1) : x_add - x_sub;
wrk->x_sub = wrk->x_expand ? (x_add - 1) : x_sub;
wrk->y_accum = y_add;
wrk->y_add = y_add;
wrk->y_sub = y_sub;
wrk->fx_scale = (1 << RFIX) / x_sub;
wrk->fy_scale = (1 << RFIX) / y_sub;
wrk->fxy_scale = wrk->x_expand ?
((int64_t)dst_height << RFIX) / (x_sub * src_height) :
((int64_t)dst_height << RFIX) / (x_add * src_height);
wrk->irow = work;
wrk->frow = work + num_channels * dst_width;
}
void WebPRescalerImportRow(WebPRescaler* const wrk,
const uint8_t* const src, int channel) {
const int x_stride = wrk->num_channels;
const int x_out_max = wrk->dst_width * wrk->num_channels;
int x_in = channel;
int x_out;
int accum = 0;
if (!wrk->x_expand) {
int sum = 0;
for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
accum += wrk->x_add;
for (; accum > 0; accum -= wrk->x_sub) {
sum += src[x_in];
x_in += x_stride;
}
{ // Emit next horizontal pixel.
const int32_t base = src[x_in];
const int32_t frac = base * (-accum);
x_in += x_stride;
wrk->frow[x_out] = (sum + base) * wrk->x_sub - frac;
// fresh fractional start for next pixel
sum = (int)MULT_FIX(frac, wrk->fx_scale);
}
}
} else { // simple bilinear interpolation
int left = src[channel], right = src[channel];
for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
if (accum < 0) {
left = right;
x_in += x_stride;
right = src[x_in];
accum += wrk->x_add;
}
wrk->frow[x_out] = right * wrk->x_add + (left - right) * accum;
accum -= wrk->x_sub;
}
}
// Accumulate the new row's contribution
for (x_out = channel; x_out < x_out_max; x_out += x_stride) {
wrk->irow[x_out] += wrk->frow[x_out];
}
}
uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk) {
if (wrk->y_accum <= 0) {
int x_out;
uint8_t* const dst = wrk->dst;
int32_t* const irow = wrk->irow;
const int32_t* const frow = wrk->frow;
const int yscale = wrk->fy_scale * (-wrk->y_accum);
const int x_out_max = wrk->dst_width * wrk->num_channels;
for (x_out = 0; x_out < x_out_max; ++x_out) {
const int frac = (int)MULT_FIX(frow[x_out], yscale);
const int v = (int)MULT_FIX(irow[x_out] - frac, wrk->fxy_scale);
dst[x_out] = (!(v & ~0xff)) ? v : (v < 0) ? 0 : 255;
irow[x_out] = frac; // new fractional start
}
wrk->y_accum += wrk->y_add;
wrk->dst += wrk->dst_stride;
return dst;
} else {
return NULL;
}
}
#undef MULT_FIX
#undef RFIX
//------------------------------------------------------------------------------
// all-in-one calls
int WebPRescaleNeededLines(const WebPRescaler* const wrk, int max_num_lines) {
const int num_lines = (wrk->y_accum + wrk->y_sub - 1) / wrk->y_sub;
return (num_lines > max_num_lines) ? max_num_lines : num_lines;
}
int WebPRescalerImport(WebPRescaler* const wrk, int num_lines,
const uint8_t* src, int src_stride) {
int total_imported = 0;
while (total_imported < num_lines && wrk->y_accum > 0) {
int channel;
for (channel = 0; channel < wrk->num_channels; ++channel) {
WebPRescalerImportRow(wrk, src, channel);
}
src += src_stride;
++total_imported;
wrk->y_accum -= wrk->y_sub;
}
return total_imported;
}
int WebPRescalerExport(WebPRescaler* const rescaler) {
int total_exported = 0;
while (WebPRescalerHasPendingOutput(rescaler)) {
WebPRescalerExportRow(rescaler);
++total_exported;
}
return total_exported;
}
//------------------------------------------------------------------------------
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