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 (at) gmail.com) 13 14 #ifndef WEBP_UTILS_RESCALER_H_ 15 #define WEBP_UTILS_RESCALER_H_ 16 17 #if defined(__cplusplus) || defined(c_plusplus) 18 extern "C" { 19 #endif 20 21 #include "../webp/types.h" 22 23 // Structure used for on-the-fly rescaling 24 typedef 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. 41 void WebPRescalerInit(WebPRescaler* const wrk, int src_width, int src_height, 42 uint8_t* const dst, 43 int dst_width, int dst_height, int dst_stride, 44 int num_channels, 45 int x_add, int x_sub, 46 int y_add, int y_sub, 47 int32_t* const work); 48 49 // Import a row of data and save its contribution in the rescaler. 50 // 'channel' denotes the channel number to be imported. 51 void WebPRescalerImportRow(WebPRescaler* const rescaler, 52 const uint8_t* const src, int channel); 53 54 // Import multiple rows over all channels, until at least one row is ready to 55 // be exported. Returns the actual number of lines that were imported. 56 int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows, 57 const uint8_t* src, int src_stride); 58 59 // Return true if there is pending output rows ready. 60 static WEBP_INLINE 61 int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) { 62 return (rescaler->y_accum <= 0); 63 } 64 65 // Export one row from rescaler. Returns the pointer where output was written, 66 // or NULL if no row was pending. 67 uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk); 68 69 // Export as many rows as possible. Return the numbers of rows written. 70 int WebPRescalerExport(WebPRescaler* const wrk); 71 72 //------------------------------------------------------------------------------ 73 74 #if defined(__cplusplus) || defined(c_plusplus) 75 } // extern "C" 76 #endif 77 78 #endif /* WEBP_UTILS_RESCALER_H_ */ 79
