Home | History | Annotate | Download | only in utils 
      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