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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 (
#if defined(__cplusplus) || defined(c_plusplus)
extern "C" {
#include "../webp/types.h"
// Structure used for on-the-fly rescaling
typedef struct {
int x_expand; // true if we're expanding in the x direction
int num_channels; // bytes to jump between pixels
int fy_scale, fx_scale; // fixed-point scaling factor
int64_t fxy_scale; // ''
// we need hpel-precise add/sub increments, for the downsampled U/V planes.
int y_accum; // vertical accumulator
int y_add, y_sub; // vertical increments (add ~= src, sub ~= dst)
int x_add, x_sub; // horizontal increments (add ~= src, sub ~= dst)
int src_width, src_height; // source dimensions
int dst_width, dst_height; // destination dimensions
uint8_t* dst;
int dst_stride;
int32_t* irow, *frow; // work buffer
} WebPRescaler;
// Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
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);
// Import a row of data and save its contribution in the rescaler.
// 'channel' denotes the channel number to be imported.
void WebPRescalerImportRow(WebPRescaler* const rescaler,
const uint8_t* const src, int channel);
// Import multiple rows over all channels, until at least one row is ready to
// be exported. Returns the actual number of lines that were imported.
int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
const uint8_t* src, int src_stride);
// Return true if there is pending output rows ready.
int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
return (rescaler->y_accum <= 0);
// Export one row from rescaler. Returns the pointer where output was written,
// or NULL if no row was pending.
uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk);
// Export as many rows as possible. Return the numbers of rows written.
int WebPRescalerExport(WebPRescaler* const wrk);
#if defined(__cplusplus) || defined(c_plusplus)
} // extern "C"