1// Copyright 2012 Google Inc. All Rights Reserved. 2// 3// Use of this source code is governed by a BSD-style license 4// that can be found in the COPYING file in the root of the source 5// tree. An additional intellectual property rights grant can be found 6// in the file PATENTS. All contributing project authors may 7// be found in the AUTHORS file in the root of the source tree. 8// ----------------------------------------------------------------------------- 9// 10// Rescaling functions 11// 12// Author: Skal (pascal.massimino@gmail.com) 13 14#ifndef WEBP_UTILS_RESCALER_H_ 15#define WEBP_UTILS_RESCALER_H_ 16 17#ifdef __cplusplus 18extern "C" { 19#endif 20 21#include "../webp/types.h" 22 23// Structure used for on-the-fly rescaling 24typedef struct { 25 int x_expand; // true if we're expanding in the x direction 26 int num_channels; // bytes to jump between pixels 27 int fy_scale, fx_scale; // fixed-point scaling factor 28 int64_t fxy_scale; // '' 29 // we need hpel-precise add/sub increments, for the downsampled U/V planes. 30 int y_accum; // vertical accumulator 31 int y_add, y_sub; // vertical increments (add ~= src, sub ~= dst) 32 int x_add, x_sub; // horizontal increments (add ~= src, sub ~= dst) 33 int src_width, src_height; // source dimensions 34 int dst_width, dst_height; // destination dimensions 35 uint8_t* dst; 36 int dst_stride; 37 int32_t* irow, *frow; // work buffer 38} WebPRescaler; 39 40// Initialize a rescaler given scratch area 'work' and dimensions of src & dst. 41void WebPRescalerInit(WebPRescaler* const rescaler, 42 int src_width, int src_height, 43 uint8_t* const dst, 44 int dst_width, int dst_height, int dst_stride, 45 int num_channels, 46 int x_add, int x_sub, 47 int y_add, int y_sub, 48 int32_t* const work); 49 50// Returns the number of input lines needed next to produce one output line, 51// considering that the maximum available input lines are 'max_num_lines'. 52int WebPRescaleNeededLines(const WebPRescaler* const rescaler, 53 int max_num_lines); 54 55// Import multiple rows over all channels, until at least one row is ready to 56// be exported. Returns the actual number of lines that were imported. 57int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows, 58 const uint8_t* src, int src_stride); 59 60// Import a row of data and save its contribution in the rescaler. 61// 'channel' denotes the channel number to be imported. 62extern void (*WebPRescalerImportRow)(WebPRescaler* const wrk, 63 const uint8_t* const src, int channel); 64// Export one row (starting at x_out position) from rescaler. 65extern void (*WebPRescalerExportRow)(WebPRescaler* const wrk, int x_out); 66 67// Return true if there is pending output rows ready. 68static WEBP_INLINE 69int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) { 70 return (rescaler->y_accum <= 0); 71} 72 73// Export as many rows as possible. Return the numbers of rows written. 74int WebPRescalerExport(WebPRescaler* const rescaler); 75 76//------------------------------------------------------------------------------ 77 78#ifdef __cplusplus 79} // extern "C" 80#endif 81 82#endif /* WEBP_UTILS_RESCALER_H_ */ 83