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