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  * Display matrix
24  */
25 
26 #ifndef AVUTIL_DISPLAY_H
27 #define AVUTIL_DISPLAY_H
28 
29 #include <stdint.h>
30 
31 /**
32  * @addtogroup lavu_video
33  * @{
34  *
35  * @defgroup lavu_video_display Display transformation matrix functions
36  * @{
37  */
38 
39 /**
40  * @addtogroup lavu_video_display
41  * The display transformation matrix specifies an affine transformation that
42  * should be applied to video frames for correct presentation. It is compatible
43  * with the matrices stored in the ISO/IEC 14496-12 container format.
44  *
45  * The data is a 3x3 matrix represented as a 9-element array:
46  *
47  * @code{.unparsed}
48  * | a b u |
49  * (a, b, u, c, d, v, x, y, w) -> | c d v |
50  * | x y w |
51  * @endcode
52  *
53  * All numbers are stored in native endianness, as 16.16 fixed-point values,
54  * except for u, v and w, which are stored as 2.30 fixed-point values.
55  *
56  * The transformation maps a point (p, q) in the source (pre-transformation)
57  * frame to the point (p', q') in the destination (post-transformation) frame as
58  * follows:
59  *
60  * @code{.unparsed}
61  * | a b u |
62  * (p, q, 1) . | c d v | = z * (p', q', 1)
63  * | x y w |
64  * @endcode
65  *
66  * The transformation can also be more explicitly written in components as
67  * follows:
68  *
69  * @code{.unparsed}
70  * p' = (a * p + c * q + x) / z;
71  * q' = (b * p + d * q + y) / z;
72  * z = u * p + v * q + w
73  * @endcode
74  */
75 
76 /**
77  * Extract the rotation component of the transformation matrix.
78  *
79  * @param matrix the transformation matrix
80  * @return the angle (in degrees) by which the transformation rotates the frame
81  * counterclockwise. The angle will be in range [-180.0, 180.0],
82  * or NaN if the matrix is singular.
83  *
84  * @note floating point numbers are inherently inexact, so callers are
85  * recommended to round the return value to nearest integer before use.
86  */
87 double av_display_rotation_get(const int32_t matrix[9]);
88 
89 /**
90  * Initialize a transformation matrix describing a pure clockwise
91  * rotation by the specified angle (in degrees).
92  *
93  * @param[out] matrix a transformation matrix (will be fully overwritten
94  * by this function)
95  * @param angle rotation angle in degrees.
96  */
97 void av_display_rotation_set(int32_t matrix[9], double angle);
98 
99 /**
100  * Flip the input matrix horizontally and/or vertically.
101  *
102  * @param[in,out] matrix a transformation matrix
103  * @param hflip whether the matrix should be flipped horizontally
104  * @param vflip whether the matrix should be flipped vertically
105  */
106 void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip);
107 
108 /**
109  * @}
110  * @}
111  */
112 
113 #endif /* AVUTIL_DISPLAY_H */
matrix
Definition: vc1dsp.c:42
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