1// Copyright 2012 Google Inc. All Rights Reserved. 2// 3// This code is licensed under the same terms as WebM: 4// Software License Agreement: http://www.webmproject.org/license/software/ 5// Additional IP Rights Grant: http://www.webmproject.org/license/additional/ 6// ----------------------------------------------------------------------------- 7// 8// Rescaling functions 9// 10// Author: Skal (pascal.massimino@gmail.com) 11 12#ifndef WEBP_UTILS_RESCALER_H_ 13#define WEBP_UTILS_RESCALER_H_ 14 15#if defined(__cplusplus) || defined(c_plusplus) 16extern "C" { 17#endif 18 19#include "webp/types.h" 20 21// Structure used for on-the-fly rescaling 22typedef struct { 23 int x_expand; // true if we're expanding in the x direction 24 int num_channels; // bytes to jump between pixels 25 int fy_scale, fx_scale; // fixed-point scaling factor 26 int64_t fxy_scale; // '' 27 // we need hpel-precise add/sub increments, for the downsampled U/V planes. 28 int y_accum; // vertical accumulator 29 int y_add, y_sub; // vertical increments (add ~= src, sub ~= dst) 30 int x_add, x_sub; // horizontal increments (add ~= src, sub ~= dst) 31 int src_width, src_height; // source dimensions 32 int dst_width, dst_height; // destination dimensions 33 uint8_t* dst; 34 int dst_stride; 35 int32_t* irow, *frow; // work buffer 36} WebPRescaler; 37 38// Initialize a rescaler given scratch area 'work' and dimensions of src & dst. 39void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height, 40 uint8_t* const dst, 41 int dst_width, int dst_height, int dst_stride, 42 int num_channels, 43 int x_add, int x_sub, 44 int y_add, int y_sub, 45 int32_t* const work); 46 47// Import a row of data and save its contribution in the rescaler. 48// 'channel' denotes the channel number to be imported. 49void WebPRescalerImportRow(WebPRescaler* const rescaler, 50 const uint8_t* const src, int channel); 51 52// Import multiple rows over all channels, until at least one row is ready to 53// be exported. Returns the actual number of lines that were imported. 54int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows, 55 const uint8_t* src, int src_stride); 56 57// Return true if there is pending output rows ready. 58static WEBP_INLINE 59int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) { 60 return (rescaler->y_accum <= 0); 61} 62 63// Export one row from rescaler. Returns the pointer where output was written, 64// or NULL if no row was pending. 65uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk); 66 67// Export as many rows as possible. Return the numbers of rows written. 68int WebPRescalerExport(WebPRescaler* const wrk); 69 70//------------------------------------------------------------------------------ 71 72#if defined(__cplusplus) || defined(c_plusplus) 73} // extern "C" 74#endif 75 76#endif /* WEBP_UTILS_RESCALER_H_ */ 77