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display.h
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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  */
88 double 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  */
98 void 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  */
107 void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip);
108 
109 /**
110  * @}
111  * @}
112  */
113 
114 #endif /* AVUTIL_DISPLAY_H */
void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip)
Flip the input matrix horizontally and/or vertically.
Definition: display.c:65
void av_display_rotation_set(int32_t matrix[9], double angle)
Initialize a transformation matrix describing a pure counterclockwise rotation by the specified angle...
Definition: display.c:50
int32_t
common internal and external API header
double av_display_rotation_get(const int32_t matrix[9])
Extract the rotation component of the transformation matrix.
Definition: display.c:34