FFmpeg/libavutil/display.c

/*
 * Copyright (c) 2014 Vittorio Giovara <vittorio.giovara@gmail.com>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <stdint.h>
#include <string.h>
#include <math.h>

#include "display.h"
#include "mathematics.h"

// fixed point to double
#define CONV_FP(x) ((double) (x)) / (1 << 16)

// double to fixed point
#define CONV_DB(x) (int32_t) ((x) * (1 << 16))

double av_display_rotation_get(const int32_t matrix[9])
{
    double rotation, scale[2];

    scale[0] = hypot(CONV_FP(matrix[0]), CONV_FP(matrix[3]));
    scale[1] = hypot(CONV_FP(matrix[1]), CONV_FP(matrix[4]));

    if (scale[0] == 0.0 || scale[1] == 0.0)
        return NAN;

    rotation = atan2(CONV_FP(matrix[1]) / scale[1],
                     CONV_FP(matrix[0]) / scale[0]) * 180 / M_PI;

    return -rotation;
}

void av_display_rotation_set(int32_t matrix[9], double angle)
{
    double radians = -angle * M_PI / 180.0f;
    double c = cos(radians);
    double s = sin(radians);

    memset(matrix, 0, 9 * sizeof(int32_t));

    matrix[0] = CONV_DB(c);
    matrix[1] = CONV_DB(-s);
    matrix[3] = CONV_DB(s);
    matrix[4] = CONV_DB(c);
    matrix[8] = 1 << 30;
}

void av_display_matrix_flip(int32_t matrix[9], int hflip, int vflip)
{
    int i;
    const int flip[] = { 1 - 2 * (!!hflip), 1 - 2 * (!!vflip), 1 };

    if (hflip || vflip)
        for (i = 0; i < 9; i++)
            matrix[i] *= flip[i % 3];
}

#ifdef TEST

static void print_matrix(int32_t matrix[9])
{
    int i, j;

    for (i = 0; i < 3; ++i) {
        for (j = 0; j < 3 - 1; ++j)
            printf("%d ", matrix[i*3 + j]);

        printf("%d\n", matrix[i*3 + j]);
    }
}

int main(void)
{
    int32_t matrix[9];

    // Set the matrix to 90 degrees
    av_display_rotation_set(matrix, 90);
    print_matrix(matrix);
    printf("degrees: %f\n", av_display_rotation_get(matrix));

    // Set the matrix to -45 degrees
    av_display_rotation_set(matrix, -45);
    print_matrix(matrix);
    printf("degrees: %f\n", av_display_rotation_get(matrix));

    // flip horizontal
    av_display_matrix_flip(matrix, 1, 0);
    print_matrix(matrix);
    printf("degrees: %f\n", av_display_rotation_get(matrix));

    // flip vertical
    av_display_matrix_flip(matrix, 0, 1);
    print_matrix(matrix);
    printf("degrees: %f\n", av_display_rotation_get(matrix));

    return 0;

}
#endif