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/*
Copyright (C) 2012 Carl Hetherington <cth@carlh.net>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/** @file src/subtitle.cc
* @brief Representations of subtitles.
*/
#include "subtitle.h"
#include "image.h"
#include "exceptions.h"
using namespace std;
using namespace boost;
/** Construct a TimedSubtitle. This is a subtitle image, position,
* and a range of time over which it should be shown.
* @param sub AVSubtitle to read.
* @param c Fractional seconds that should be subtracted from the AVSubtitle's PTS.
*/
TimedSubtitle::TimedSubtitle (AVSubtitle const & sub, double c)
{
assert (sub.rects > 0);
/* subtitle PTS in seconds */
double const packet_time = ((sub.pts / AV_TIME_BASE) + float (sub.pts % AV_TIME_BASE) / 1e6) - c;
/* hence start time for this sub */
_from = packet_time + (double (sub.start_display_time) / 1e3);
_to = packet_time + (double (sub.end_display_time) / 1e3);
if (sub.num_rects > 1) {
throw DecodeError ("multi-part subtitles not yet supported");
}
AVSubtitleRect const * rect = sub.rects[0];
if (rect->type != SUBTITLE_BITMAP) {
throw DecodeError ("non-bitmap subtitles not yet supported");
}
shared_ptr<Image> image (new AlignedImage (PIX_FMT_RGBA, Size (rect->w, rect->h)));
/* Start of the first line in the subtitle */
uint8_t* sub_p = rect->pict.data[0];
/* sub_p looks up into a RGB palette which is here */
uint32_t const * palette = (uint32_t *) rect->pict.data[1];
/* Start of the output data */
uint32_t* out_p = (uint32_t *) image->data()[0];
for (int y = 0; y < rect->h; ++y) {
uint8_t* sub_line_p = sub_p;
uint32_t* out_line_p = out_p;
for (int x = 0; x < rect->w; ++x) {
*out_line_p++ = palette[*sub_line_p++];
}
sub_p += rect->pict.linesize[0];
out_p += image->stride()[0] / sizeof (uint32_t);
}
_subtitle.reset (new Subtitle (Position (rect->x, rect->y), image));
}
/** @param t Time in seconds from the start of the film */
bool
TimedSubtitle::displayed_at (double t) const
{
return t >= _from && t <= _to;
}
/** Construct a subtitle, which is an image and a position.
* @param p Position within the (uncropped) source frame.
* @param i Image of the subtitle (should be RGBA).
*/
Subtitle::Subtitle (Position p, shared_ptr<Image> i)
: _position (p)
, _image (i)
{
}
/** Given the area of a subtitle, work out the area it should
* take up when its video frame is scaled up, and it is optionally
* itself scaled and offset.
* @param target_x_scale the x scaling of the video frame that the subtitle is in.
* @param target_y_scale the y scaling of the video frame that the subtitle is in.
* @param sub_area The area of the subtitle within the original source.
* @param subtitle_offset y offset to apply to the subtitle position (+ve is down)
* in the coordinate space of the source.
* @param subtitle_scale scaling factor to apply to the subtitle image.
*/
Rect
subtitle_transformed_area (
float target_x_scale, float target_y_scale,
Rect sub_area, int subtitle_offset, float subtitle_scale
)
{
Rect tx;
sub_area.y += subtitle_offset;
/* We will scale the subtitle by the same amount as the video frame, and also by the additional
subtitle_scale
*/
tx.width = sub_area.width * target_x_scale * subtitle_scale;
tx.height = sub_area.height * target_y_scale * subtitle_scale;
/* Then we need a corrective translation, consisting of two parts:
*
* 1. that which is the result of the scaling of the subtitle by target_x_scale and target_y_scale; this will be
* sub_area.x * target_x_scale and sub_area.y * target_y_scale.
*
* 2. that to shift the origin of the scale by subtitle_scale to the centre of the subtitle; this will be
* (width_before_subtitle_scale * (1 - subtitle_scale) / 2) and
* (height_before_subtitle_scale * (1 - subtitle_scale) / 2).
*
* Combining these two translations gives these expressions.
*/
tx.x = target_x_scale * (sub_area.x + (sub_area.width * (1 - subtitle_scale) / 2));
tx.y = target_y_scale * (sub_area.y + (sub_area.height * (1 - subtitle_scale) / 2));
return tx;
}
/** @return area that this subtitle take up, in the original uncropped source's coordinate space */
Rect
Subtitle::area () const
{
return Rect (_position.x, _position.y, _image->size().width, _image->size().height);
}
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