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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.  *         counterclockwise. The angle will be in range [-180.0, 180.0],
  60.  *         or NaN if the matrix is 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 counterclockwise
  69.  * rotation by the 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 */
  87.