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 (at) gmail.com) 11 12 #ifndef WEBP_UTILS_RESCALER_H_ 13 #define WEBP_UTILS_RESCALER_H_ 14 15 #if defined(__cplusplus) || defined(c_plusplus) 16 extern "C" { 17 #endif 18 19 #include "webp/types.h" 20 21 // Structure used for on-the-fly rescaling 22 typedef 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. 39 void 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. 49 void 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. 54 int 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. 58 static WEBP_INLINE 59 int 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. 65 uint8_t* WebPRescalerExportRow(WebPRescaler* const wrk); 66 67 // Export as many rows as possible. Return the numbers of rows written. 68 int 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