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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 #ifndef AVUTIL_DISPLAY_H
22 #define AVUTIL_DISPLAY_H
23 
24 #include <stdint.h>
25 
26 /**
27  * The display transformation matrix specifies an affine transformation that
28  * should be applied to video frames for correct presentation. It is compatible
29  * with the matrices stored in the ISO/IEC 14496-12 container format.
30  *
31  * The data is a 3x3 matrix represented as a 9-element array:
32  *
33  * | a b u |
34  * (a, b, u, c, d, v, x, y, w) -> | c d v |
35  * | x y w |
36  *
37  * All numbers are stored in native endianness, as 16.16 fixed-point values,
38  * except for u, v and w, which are stored as 2.30 fixed-point values.
39  *
40  * The transformation maps a point (p, q) in the source (pre-transformation)
41  * frame to the point (p', q') in the destination (post-transformation) frame as
42  * follows:
43  * | a b u |
44  * (p, q, 1) . | c d v | = z * (p', q', 1)
45  * | x y w |
46  *
47  * The transformation can also be more explicitly written in components as
48  * follows:
49  * p' = (a * p + c * q + x) / z;
50  * q' = (b * p + d * q + y) / z;
51  * z = u * p + v * q + w
52  */
53 
54 /**
55  * Extract the rotation component of the transformation matrix.
56  *
57  * @param matrix the transformation matrix
58  * @return the angle (in degrees) by which the transformation rotates the frame.
59  * The angle will be in range [-180.0, 180.0], or NaN if the matrix is
60  * singular.
61  *
62  * @note floating point numbers are inherently inexact, so callers are
63  * recommended to round the return value to nearest integer before use.
64  */
65 double av_display_rotation_get(const int32_t matrix[9]);
66 
67 /**
68  * Initialize a transformation matrix describing a pure rotation by the
69  * specified angle (in degrees).
70  *
71  * @param matrix an allocated transformation matrix (will be fully overwritten
72  * by this function)
73  * @param angle rotation angle in degrees.
74  */
75 void av_display_rotation_set(int32_t matrix[9], double angle);
76 
77 /**
78  * Flip the input matrix horizontally and/or vertically.
79  *
80  * @param matrix an allocated transformation matrix
81  * @param hflip whether the matrix should be flipped horizontally
82  * @param vflip whether the matrix should be flipped vertically
83  */
84 void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip);
85 
86 #endif /* AVUTIL_DISPLAY_H */