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_UTILS_H_
15#define WEBP_UTILS_RESCALER_UTILS_H_
16
17#ifdef __cplusplus
18extern "C" {
19#endif
20
21#include "src/webp/types.h"
22
23#define WEBP_RESCALER_RFIX 32   // fixed-point precision for multiplies
24#define WEBP_RESCALER_ONE (1ull << WEBP_RESCALER_RFIX)
25#define WEBP_RESCALER_FRAC(x, y) \
26    ((uint32_t)(((uint64_t)(x) << WEBP_RESCALER_RFIX) / (y)))
27
28// Structure used for on-the-fly rescaling
29typedef uint32_t rescaler_t;   // type for side-buffer
30typedef struct WebPRescaler WebPRescaler;
31struct WebPRescaler {
32  int x_expand;               // true if we're expanding in the x direction
33  int y_expand;               // true if we're expanding in the y direction
34  int num_channels;           // bytes to jump between pixels
35  uint32_t fx_scale;          // fixed-point scaling factors
36  uint32_t fy_scale;          // ''
37  uint32_t fxy_scale;         // ''
38  int y_accum;                // vertical accumulator
39  int y_add, y_sub;           // vertical increments
40  int x_add, x_sub;           // horizontal increments
41  int src_width, src_height;  // source dimensions
42  int dst_width, dst_height;  // destination dimensions
43  int src_y, dst_y;           // row counters for input and output
44  uint8_t* dst;
45  int dst_stride;
46  rescaler_t* irow, *frow;    // work buffer
47};
48
49// Initialize a rescaler given scratch area 'work' and dimensions of src & dst.
50void WebPRescalerInit(WebPRescaler* const rescaler,
51                      int src_width, int src_height,
52                      uint8_t* const dst,
53                      int dst_width, int dst_height, int dst_stride,
54                      int num_channels,
55                      rescaler_t* const work);
56
57// If either 'scaled_width' or 'scaled_height' (but not both) is 0 the value
58// will be calculated preserving the aspect ratio, otherwise the values are
59// left unmodified. Returns true on success, false if either value is 0 after
60// performing the scaling calculation.
61int WebPRescalerGetScaledDimensions(int src_width, int src_height,
62                                    int* const scaled_width,
63                                    int* const scaled_height);
64
65// Returns the number of input lines needed next to produce one output line,
66// considering that the maximum available input lines are 'max_num_lines'.
67int WebPRescaleNeededLines(const WebPRescaler* const rescaler,
68                           int max_num_lines);
69
70// Import multiple rows over all channels, until at least one row is ready to
71// be exported. Returns the actual number of lines that were imported.
72int WebPRescalerImport(WebPRescaler* const rescaler, int num_rows,
73                       const uint8_t* src, int src_stride);
74
75// Export as many rows as possible. Return the numbers of rows written.
76int WebPRescalerExport(WebPRescaler* const rescaler);
77
78// Return true if input is finished
79static WEBP_INLINE
80int WebPRescalerInputDone(const WebPRescaler* const rescaler) {
81  return (rescaler->src_y >= rescaler->src_height);
82}
83// Return true if output is finished
84static WEBP_INLINE
85int WebPRescalerOutputDone(const WebPRescaler* const rescaler) {
86  return (rescaler->dst_y >= rescaler->dst_height);
87}
88
89// Return true if there are pending output rows ready.
90static WEBP_INLINE
91int WebPRescalerHasPendingOutput(const WebPRescaler* const rescaler) {
92  return !WebPRescalerOutputDone(rescaler) && (rescaler->y_accum <= 0);
93}
94
95//------------------------------------------------------------------------------
96
97#ifdef __cplusplus
98}    // extern "C"
99#endif
100
101#endif  /* WEBP_UTILS_RESCALER_UTILS_H_ */
102