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 #ifdef __cplusplus 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 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'. 52 int 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. 57 int 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. 62 extern void (*WebPRescalerImportRow)(WebPRescaler* const wrk, 63 const uint8_t* const src, int channel); 64 // Export one row (starting at x_out position) from rescaler. 65 extern void (*WebPRescalerExportRow)(WebPRescaler* const wrk, int x_out); 66 67 // Return true if there is pending output rows ready. 68 static WEBP_INLINE 69 int 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. 74 int WebPRescalerExport(WebPRescaler* const rescaler); 75 76 //------------------------------------------------------------------------------ 77 78 #ifdef __cplusplus 79 } // extern "C" 80 #endif 81 82 #endif /* WEBP_UTILS_RESCALER_H_ */ 83
