Basics of subtitle rendering.

1 files changed, 150 insertions, 0 deletions

diff --git a/src/lib/render_subtitles.cc b/src/lib/render_subtitles.cc
new file mode 100644
index 000000000..630681761
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+++ b/src/lib/render_subtitles.cc
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+/*
+    Copyright (C) 2014 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.
+
+*/
+
+#include <cairomm/cairomm.h>
+#include <pangomm.h>
+#include "render_subtitles.h"
+#include "types.h"
+#include "image.h"
+
+using std::list;
+using std::cout;
+using std::string;
+using std::min;
+using std::max;
+using boost::shared_ptr;
+using boost::optional;
+
+static int
+calculate_position (libdcp::VAlign v_align, double v_position, int target_height, int offset)
+{
+	switch (v_align) {
+	case libdcp::TOP:
+		return (v_position / 100) * target_height - offset;
+	case libdcp::CENTER:
+		return (0.5 + v_position / 100) * target_height - offset;
+	case libdcp::BOTTOM:
+		return (1.0 - v_position / 100) * target_height - offset;
+	}
+
+	return 0;
+}
+
+void
+render_subtitles (list<libdcp::Subtitle> subtitles, libdcp::Size target, shared_ptr<Image>& image, Position<int>& position)
+{
+	if (subtitles.empty ()) {
+		image.reset ();
+		return;
+	}
+
+	/* Estimate height that the subtitle image needs to be */
+	optional<int> top;
+	optional<int> bottom;
+	for (list<libdcp::Subtitle>::const_iterator i = subtitles.begin(); i != subtitles.end(); ++i) {
+		int const b = calculate_position (i->v_align(), i->v_position(), target.height, 0);
+		int const t = b - i->size() * target.height / (11 * 72);
+
+		top = min (top.get_value_or (t), t);
+		bottom = max (bottom.get_value_or (b), b);
+	}
+
+	top = top.get() - 32;
+	bottom = bottom.get() + 32;
+
+	image.reset (new Image (PIX_FMT_RGBA, libdcp::Size (target.width, bottom.get() - top.get ()), false));
+	image->make_black ();
+
+	Cairo::RefPtr<Cairo::ImageSurface> surface = Cairo::ImageSurface::create (
+		image->data()[0],
+		Cairo::FORMAT_ARGB32,
+		image->size().width,
+		image->size().height,
+		Cairo::ImageSurface::format_stride_for_width (Cairo::FORMAT_ARGB32, image->size().width)
+		);
+	
+	Cairo::RefPtr<Cairo::Context> context = Cairo::Context::create (surface);
+	Glib::RefPtr<Pango::Layout> layout = Pango::Layout::create (context);
+
+	layout->set_width (image->size().width * PANGO_SCALE);
+	layout->set_alignment (Pango::ALIGN_CENTER);
+
+	context->set_line_width (1);
+
+	for (list<libdcp::Subtitle>::const_iterator i = subtitles.begin(); i != subtitles.end(); ++i) {
+		string f = i->font ();
+		if (f.empty ()) {
+			f = "Arial";
+		}
+		Pango::FontDescription font (f);
+		font.set_absolute_size (i->size_in_pixels (target.height) * PANGO_SCALE);
+		if (i->italic ()) {
+			font.set_style (Pango::STYLE_ITALIC);
+		}
+		layout->set_font_description (font);
+		layout->set_text (i->text ());
+
+		/* Compute fade factor */
+		/* XXX */
+		float fade_factor = 1;
+#if 0		
+		libdcp::Time now (time * 1000 / (4 * TIME_HZ));
+		libdcp::Time end_fade_up = i->in() + i->fade_up_time ();
+		libdcp::Time start_fade_down = i->out() - i->fade_down_time ();
+		if (now < end_fade_up) {
+			fade_factor = (now - i->in()) / i->fade_up_time();
+		} else if (now > start_fade_down) {
+			fade_factor = 1.0 - ((now - start_fade_down) / i->fade_down_time ());
+		}
+#endif		
+
+		layout->update_from_cairo_context (context);
+		
+		/* Work out position */
+
+		int const x = 0;
+		int const y = calculate_position (i->v_align (), i->v_position (), target.height, (layout->get_baseline() / PANGO_SCALE) + top.get ());
+
+		if (i->effect() == libdcp::SHADOW) {
+			/* Drop-shadow effect */
+			libdcp::Color const ec = i->effect_color ();
+			context->set_source_rgba (float(ec.r) / 255, float(ec.g) / 255, float(ec.b) / 255, fade_factor);
+			context->move_to (x + 4, y + 4);
+			layout->add_to_cairo_context (context);
+			context->fill ();
+		}
+
+		/* The actual subtitle */
+		context->move_to (x, y);
+		libdcp::Color const c = i->color ();
+		context->set_source_rgba (float(c.r) / 255, float(c.g) / 255, float(c.b) / 255, fade_factor);
+		layout->add_to_cairo_context (context);
+		context->fill ();
+
+		if (i->effect() == libdcp::BORDER) {
+			/* Border effect */
+			context->move_to (x, y);
+			libdcp::Color ec = i->effect_color ();
+			context->set_source_rgba (float(ec.r) / 255, float(ec.g) / 255, float(ec.b) / 255, fade_factor);
+			layout->add_to_cairo_context (context);
+			context->stroke ();
+		}
+	}
+}
+