1/*
2 * Copyright (c) 2014 Vittorio Giovara <vittorio.giovara@gmail.com>
3 *
4 * This file is part of FFmpeg.
5 *
6 * FFmpeg is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * FFmpeg is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with FFmpeg; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19 */
20
21/**
22 * @file
23 * Display matrix
24 */
25
26#ifndef AVUTIL_DISPLAY_H
27#define AVUTIL_DISPLAY_H
28
29#include <stdint.h>
30#include "common.h"
31
32/**
33 * @addtogroup lavu_video
34 * @{
35 *
36 * @defgroup lavu_video_display Display transformation matrix functions
37 * @{
38 */
39
40/**
41 * @addtogroup lavu_video_display
42 * The display transformation matrix specifies an affine transformation that
43 * should be applied to video frames for correct presentation. It is compatible
44 * with the matrices stored in the ISO/IEC 14496-12 container format.
45 *
46 * The data is a 3x3 matrix represented as a 9-element array:
47 *
48 * @code{.unparsed}
49 * | a b u |
50 * (a, b, u, c, d, v, x, y, w) -> | c d v |
51 * | x y w |
52 * @endcode
53 *
54 * All numbers are stored in native endianness, as 16.16 fixed-point values,
55 * except for u, v and w, which are stored as 2.30 fixed-point values.
56 *
57 * The transformation maps a point (p, q) in the source (pre-transformation)
58 * frame to the point (p', q') in the destination (post-transformation) frame as
59 * follows:
60 *
61 * @code{.unparsed}
62 * | a b u |
63 * (p, q, 1) . | c d v | = z * (p', q', 1)
64 * | x y w |
65 * @endcode
66 *
67 * The transformation can also be more explicitly written in components as
68 * follows:
69 *
70 * @code{.unparsed}
71 * p' = (a * p + c * q + x) / z;
72 * q' = (b * p + d * q + y) / z;
73 * z = u * p + v * q + w
74 * @endcode
75 */
76
77/**
78 * Extract the rotation component of the transformation matrix.
79 *
80 * @param matrix the transformation matrix
81 * @return the angle (in degrees) by which the transformation rotates the frame
82 * counterclockwise. The angle will be in range [-180.0, 180.0],
83 * or NaN if the matrix is singular.
84 *
85 * @note floating point numbers are inherently inexact, so callers are
86 * recommended to round the return value to nearest integer before use.
87 */
88double av_display_rotation_get(const int32_t matrix[9]);
89
90/**
91 * Initialize a transformation matrix describing a pure counterclockwise
92 * rotation by the specified angle (in degrees).
93 *
94 * @param matrix an allocated transformation matrix (will be fully overwritten
95 * by this function)
96 * @param angle rotation angle in degrees.
97 */
98void av_display_rotation_set(int32_t matrix[9], double angle);
99
100/**
101 * Flip the input matrix horizontally and/or vertically.
102 *
103 * @param matrix an allocated transformation matrix
104 * @param hflip whether the matrix should be flipped horizontally
105 * @param vflip whether the matrix should be flipped vertically
106 */
107void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip);
108
109/**
110 * @}
111 * @}
112 */
113
114#endif /* AVUTIL_DISPLAY_H */
115

source code of include/x86_64-linux-gnu/libavutil/display.h