third_party/libwebp/utils/rescaler.h

   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@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 a row of data and save its contribution in the rescaler.
  56 // 'channel' denotes the channel number to be imported.
  57 void WebPRescalerImportRow(WebPRescaler* const rescaler,
  58                            const uint8_t* const src, int channel);
  59
  60 // Import multiple rows over all channels, until at least one row is ready to
  61 // be exported. Returns the actual number of lines that were imported.
  62 int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
  63                        const uint8_t* src, int src_stride);
  64
  65 // Return true if there is pending output rows ready.
  66 static WEBP_INLINE
  67 int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
  68   return (rescaler->y_accum <= 0);
  69 }
  70
  71 // Export one row from rescaler. Returns the pointer where output was written,
  72 // or NULL if no row was pending.
  73 uint8_t* WebPRescalerExportRow(WebPRescaler* const rescaler);
  74
  75 // Export as many rows as possible. Return the numbers of rows written.
  76 int WebPRescalerExport(WebPRescaler* const rescaler);
  77
  78 //------------------------------------------------------------------------------
  79
  80 #ifdef __cplusplus
  81 }    // extern "C"
  82 #endif
  83
  84 #endif  /* WEBP_UTILS_RESCALER_H_ */