lavc: add a librsvg rasterization library wrapper

Enables rendering of SVG images. This is possible since SVG images
still contain and specify the dimensions in pixels to which they've
been drawn to and thus enable browsers to display them without any
external data. Users can still override and generate images with
arbitrary resolutions.
Signed-off-by: Rostislav Pehlivanov <atomnuker@gmail.com>

Changelog

@@ -11,6 +11,7 @@ version <next>:
 - update cuvid/nvenc headers to Video Codec SDK 8.0.14
 - afir audio filter
 - scale_cuda CUDA based video scale filter
+- librsvg support for svg rasterization
 
 version 3.3:
 - CrystalHD decoder moved to new decode API

configure

@@ -245,6 +245,7 @@ External library support:
   --enable-libopenmpt      enable decoding tracked files via libopenmpt [no]
   --enable-libopus         enable Opus de/encoding via libopus [no]
   --enable-libpulse        enable Pulseaudio input via libpulse [no]
+  --enable-librsvg         enable SVG rasterization via librsvg [no]
   --enable-librubberband   enable rubberband needed for rubberband filter [no]
   --enable-librtmp         enable RTMP[E] support via librtmp [no]
   --enable-libschroedinger enable Dirac de/encoding via libschroedinger [no]
@@ -1560,6 +1561,7 @@ EXTERNAL_LIBRARY_LIST="
     libopenmpt
     libopus
     libpulse
+    librsvg
     librtmp
     libschroedinger
     libshine
@@ -2875,6 +2877,7 @@ libopenmpt_demuxer_deps="libopenmpt"
 libopus_decoder_deps="libopus"
 libopus_encoder_deps="libopus"
 libopus_encoder_select="audio_frame_queue"
+librsvg_decoder_deps="librsvg"
 libschroedinger_decoder_deps="libschroedinger"
 libschroedinger_encoder_deps="libschroedinger"
 libshine_encoder_deps="libshine"
@@ -5837,6 +5840,7 @@ enabled libopus           && {
     }
 }
 enabled libpulse          && require_pkg_config libpulse pulse/pulseaudio.h pa_context_new
+enabled librsvg           && require_pkg_config librsvg-2.0 librsvg-2.0/librsvg/rsvg.h rsvg_handle_render_cairo
 enabled librtmp           && require_pkg_config librtmp librtmp/rtmp.h RTMP_Socket
 enabled librubberband     && require_pkg_config "rubberband >= 1.8.1" rubberband/rubberband-c.h rubberband_new
 enabled libschroedinger   && require_pkg_config schroedinger-1.0 schroedinger/schro.h schro_init

libavcodec/Makefile

@@ -551,6 +551,7 @@ OBJS-$(CONFIG_SUBVIEWER1_DECODER)      += textdec.o ass.o
 OBJS-$(CONFIG_SUBVIEWER_DECODER)       += subviewerdec.o ass.o
 OBJS-$(CONFIG_SUNRAST_DECODER)         += sunrast.o
 OBJS-$(CONFIG_SUNRAST_ENCODER)         += sunrastenc.o
+OBJS-$(CONFIG_LIBRSVG_DECODER)         += librsvgdec.o
 OBJS-$(CONFIG_SVQ1_DECODER)            += svq1dec.o svq1.o svq13.o h263data.o
 OBJS-$(CONFIG_SVQ1_ENCODER)            += svq1enc.o svq1.o  h263data.o  \
                                           h263.o ituh263enc.o

libavcodec/allcodecs.c

@@ -319,6 +319,7 @@ static void register_all(void)
     REGISTER_DECODER(SPEEDHQ,           speedhq);
     REGISTER_DECODER(SRGC,              srgc);
     REGISTER_ENCDEC (SUNRAST,           sunrast);
+    REGISTER_DECODER(LIBRSVG,           librsvg);
     REGISTER_ENCDEC (SVQ1,              svq1);
     REGISTER_DECODER(SVQ3,              svq3);
     REGISTER_ENCDEC (TARGA,             targa);

libavcodec/librsvgdec.c

+/*
+ * Librsvg rasterization wrapper
+ * Copyright (c) 2017 Rostislav Pehlivanov <atomnuker@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 "avcodec.h"
+#include "internal.h"
+#include "libavutil/opt.h"
+#include "librsvg-2.0/librsvg/rsvg.h"
+
+typedef struct LibRSVGContext {
+    AVClass *class;
+
+    int width;
+    int height;
+    int keep_ar;
+} LibRSVGContext;
+
+static int librsvg_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *pkt)
+{
+    int ret;
+    LibRSVGContext *s = avctx->priv_data;
+    AVFrame *frame = data;
+
+    RsvgHandle *handle;
+    RsvgDimensionData unscaled_dimensions, dimensions;
+    cairo_surface_t *image;
+    cairo_t *crender = NULL;
+    GError *error = NULL;
+
+    *got_frame = 0;
+
+    handle = rsvg_handle_new_from_data(pkt->data, pkt->size, &error);
+    if (error) {
+        av_log(avctx, AV_LOG_ERROR, "Error parsing svg!\n");
+        g_error_free(error);
+        return AVERROR_INVALIDDATA;
+    }
+
+    rsvg_handle_get_dimensions(handle, &dimensions);
+    rsvg_handle_get_dimensions(handle, &unscaled_dimensions);
+    dimensions.width  = s->width  ? s->width  : dimensions.width;
+    dimensions.height = s->height ? s->height : dimensions.height;
+    if (s->keep_ar && (s->width || s->height)) {
+        double default_ar = unscaled_dimensions.width/(double)unscaled_dimensions.height;
+        if (!s->width)
+            dimensions.width  = lrintf(dimensions.height * default_ar);
+        else
+            dimensions.height = lrintf(dimensions.width  / default_ar);
+    }
+
+    if ((ret = ff_set_dimensions(avctx, dimensions.width, dimensions.height)))
+        return ret;
+    avctx->pix_fmt = AV_PIX_FMT_BGRA;
+
+    if ((ret = ff_get_buffer(avctx, frame, 0)))
+        return ret;
+    frame->pict_type = AV_PICTURE_TYPE_I;
+    frame->key_frame = 1;
+
+    image = cairo_image_surface_create_for_data(frame->data[0], CAIRO_FORMAT_ARGB32,
+                                                frame->width, frame->height,
+                                                frame->linesize[0]);
+    if (cairo_surface_status(image) != CAIRO_STATUS_SUCCESS)
+        return AVERROR_INVALIDDATA;
+
+    crender = cairo_create(image);
+
+    cairo_set_source_rgba(crender, 0.0, 0.0, 0.0, 1.0f);
+    cairo_paint_with_alpha(crender, 0.0f);
+
+    cairo_scale(crender, dimensions.width / (double)unscaled_dimensions.width,
+                dimensions.height / (double)unscaled_dimensions.height);
+
+    rsvg_handle_render_cairo(handle, crender);
+
+    cairo_destroy(crender);
+    cairo_surface_destroy(image);
+    g_object_unref(handle);
+
+    *got_frame = 1;
+
+    return 0;
+}
+
+#define OFFSET(x) offsetof(LibRSVGContext, x)
+#define DEC (AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_VIDEO_PARAM)
+static const AVOption options[] = {
+    { "width", "Width to render to (0 for default)", OFFSET(width), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, DEC },
+    { "height", "Height to render to (0 for default)", OFFSET(height), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, DEC },
+    { "keep_ar", "Keep aspect ratio with custom width/height", OFFSET(keep_ar), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, DEC },
+    { NULL },
+};
+
+static const AVClass librsvg_decoder_class = {
+    .class_name = "Librsvg",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
+AVCodec ff_librsvg_decoder = {
+    .name           = "librsvg",
+    .long_name      = NULL_IF_CONFIG_SMALL("Librsvg rasterizer"),
+    .priv_class     = &librsvg_decoder_class,
+    .type           = AVMEDIA_TYPE_VIDEO,
+    .id             = AV_CODEC_ID_SVG,
+    .decode         = librsvg_decode_frame,
+    .priv_data_size = sizeof(LibRSVGContext),
+    .capabilities   = AV_CODEC_CAP_LOSSLESS | AV_CODEC_CAP_DR1,
+};