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
18extern "C" {
19#endif
20
21#include "../webp/types.h"
22
23// Structure used for on-the-fly rescaling
24typedef 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.
41void 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'.
52int 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.
57int 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.
62extern void (*WebPRescalerImportRow)(WebPRescaler* const wrk,
63                                     const uint8_t* const src, int channel);
64// Export one row (starting at x_out position) from rescaler.
65extern void (*WebPRescalerExportRow)(WebPRescaler* const wrk, int x_out);
66
67// Return true if there is pending output rows ready.
68static WEBP_INLINE
69int 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.
74int WebPRescalerExport(WebPRescaler* const rescaler);
75
76//------------------------------------------------------------------------------
77
78#ifdef __cplusplus
79}    // extern "C"
80#endif
81
82#endif  /* WEBP_UTILS_RESCALER_H_ */
83