FFmpeg
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  * @ingroup lavu_video_display
24  * Display matrix
25  */
26 
27 #ifndef AVUTIL_DISPLAY_H
28 #define AVUTIL_DISPLAY_H
29 
30 #include <stdint.h>
31 
32 /**
33  * @defgroup lavu_video_display Display transformation matrix functions
34  * @ingroup lavu_video
35  *
36  * The display transformation matrix specifies an affine transformation that
37  * should be applied to video frames for correct presentation. It is compatible
38  * with the matrices stored in the ISO/IEC 14496-12 container format.
39  *
40  * The data is a 3x3 matrix represented as a 9-element array:
41  *
42  * @code{.unparsed}
43  * | a b u |
44  * (a, b, u, c, d, v, x, y, w) -> | c d v |
45  * | x y w |
46  * @endcode
47  *
48  * All numbers are stored in native endianness, as 16.16 fixed-point values,
49  * except for u, v and w, which are stored as 2.30 fixed-point values.
50  *
51  * The transformation maps a point (p, q) in the source (pre-transformation)
52  * frame to the point (p', q') in the destination (post-transformation) frame as
53  * follows:
54  *
55  * @code{.unparsed}
56  * | a b u |
57  * (p, q, 1) . | c d v | = z * (p', q', 1)
58  * | x y w |
59  * @endcode
60  *
61  * The transformation can also be more explicitly written in components as
62  * follows:
63  *
64  * @code{.unparsed}
65  * p' = (a * p + c * q + x) / z;
66  * q' = (b * p + d * q + y) / z;
67  * z = u * p + v * q + w
68  * @endcode
69  *
70  * @{
71  */
72 
73 /**
74  * Extract the rotation component of the transformation matrix.
75  *
76  * @param matrix the transformation matrix
77  * @return the angle (in degrees) by which the transformation rotates the frame
78  * counterclockwise. The angle will be in range [-180.0, 180.0],
79  * or NaN if the matrix is singular.
80  *
81  * @note floating point numbers are inherently inexact, so callers are
82  * recommended to round the return value to nearest integer before use.
83  */
84 double av_display_rotation_get(const int32_t matrix[9]);
85 
86 /**
87  * Initialize a transformation matrix describing a pure clockwise
88  * rotation by the specified angle (in degrees).
89  *
90  * @param[out] matrix a transformation matrix (will be fully overwritten
91  * by this function)
92  * @param angle rotation angle in degrees.
93  */
94 void av_display_rotation_set(int32_t matrix[9], double angle);
95 
96 /**
97  * Flip the input matrix horizontally and/or vertically.
98  *
99  * @param[in,out] matrix a transformation matrix
100  * @param hflip whether the matrix should be flipped horizontally
101  * @param vflip whether the matrix should be flipped vertically
102  */
103 void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip);
104 
105 /**
106  * @}
107  */
108 
109 #endif /* AVUTIL_DISPLAY_H */
matrix
Definition: vc1dsp.c:43
av_display_matrix_flip
void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip)
Flip the input matrix horizontally and/or vertically.
Definition: display.c:66
av_display_rotation_set
void av_display_rotation_set(int32_t matrix[9], double angle)
Initialize a transformation matrix describing a pure clockwise rotation by the specified angle (in de...
Definition: display.c:51
int32_t
int32_t
Definition: audioconvert.c:56
av_display_rotation_get
double av_display_rotation_get(const int32_t matrix[9])
Extract the rotation component of the transformation matrix.
Definition: display.c:35