avfilter: add ocr filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Changelog

@@ -4,6 +4,7 @@ releases are sorted from youngest to oldest.
 version <next>:
 - DXV decoding
 - extrastereo filter
+- ocr filter
 
 
 version 2.8:

configure

@@ -246,6 +246,7 @@ External library support:
   --enable-libspeex        enable Speex de/encoding via libspeex [no]
   --enable-libssh          enable SFTP protocol via libssh [no]
   --enable-libstagefright-h264  enable H.264 decoding via libstagefright [no]
+  --enable-libtesseract    enable Tesseract, needed for ocr filter [no]
   --enable-libtheora       enable Theora encoding via libtheora [no]
   --enable-libtwolame      enable MP2 encoding via libtwolame [no]
   --enable-libutvideo      enable Ut Video encoding and decoding via libutvideo [no]
@@ -1409,6 +1410,7 @@ EXTERNAL_LIBRARY_LIST="
     libspeex
     libssh
     libstagefright_h264
+    libtesseract
     libtheora
     libtwolame
     libutvideo
@@ -2774,6 +2776,7 @@ mptestsrc_filter_deps="gpl"
 negate_filter_deps="lut_filter"
 perspective_filter_deps="gpl"
 pp7_filter_deps="gpl"
+ocr_filter_deps="libtesseract"
 ocv_filter_deps="libopencv"
 owdenoise_filter_deps="gpl"
 pan_filter_deps="swresample"
@@ -5275,6 +5278,7 @@ enabled libspeex          && require_pkg_config speex speex/speex.h speex_decode
 enabled libstagefright_h264 && require_cpp libstagefright_h264 "binder/ProcessState.h media/stagefright/MetaData.h
     media/stagefright/MediaBufferGroup.h media/stagefright/MediaDebug.h media/stagefright/MediaDefs.h
     media/stagefright/OMXClient.h media/stagefright/OMXCodec.h" android::OMXClient -lstagefright -lmedia -lutils -lbinder -lgnustl_static
+enabled libtesseract      && require_pkg_config tesseract tesseract/capi.h TessBaseAPICreate
 enabled libtheora         && require libtheora theora/theoraenc.h th_info_init -ltheoraenc -ltheoradec -logg
 enabled libtwolame        && require libtwolame twolame.h twolame_init -ltwolame &&
                              { check_lib twolame.h twolame_encode_buffer_float32_interleaved -ltwolame ||

doc/filters.texi

@@ -7485,6 +7485,30 @@ noise=alls=20:allf=t+u
 
 Pass the video source unchanged to the output.
 
+@section ocr
+Optical Character Recognition
+
+This filter uses Tesseract for optical character recognition.
+
+It accepts the following options:
+
+@table @option
+@item datapath
+Set datapath to tesseract data. Default is to use whatever was
+set at installation.
+
+@item language
+Set language, default is "eng".
+
+@item whitelist
+Set character whitelist.
+
+@item blacklist
+Set character blacklist.
+@end table
+
+The filter exports recognized text as the frame metadata @code{lavfi.ocr.text}.
+
 @section ocv
 
 Apply a video transform using libopencv.

libavfilter/Makefile

@@ -169,6 +169,7 @@ OBJS-$(CONFIG_NEGATE_FILTER)                 += vf_lut.o
 OBJS-$(CONFIG_NOFORMAT_FILTER)               += vf_format.o
 OBJS-$(CONFIG_NOISE_FILTER)                  += vf_noise.o
 OBJS-$(CONFIG_NULL_FILTER)                   += vf_null.o
+OBJS-$(CONFIG_OCR_FILTER)                    += vf_ocr.o
 OBJS-$(CONFIG_OCV_FILTER)                    += vf_libopencv.o
 OBJS-$(CONFIG_OPENCL)                        += deshake_opencl.o unsharp_opencl.o
 OBJS-$(CONFIG_OVERLAY_FILTER)                += vf_overlay.o dualinput.o framesync.o

libavfilter/allfilters.c

@@ -191,6 +191,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(NOFORMAT,       noformat,       vf);
     REGISTER_FILTER(NOISE,          noise,          vf);
     REGISTER_FILTER(NULL,           null,           vf);
+    REGISTER_FILTER(OCR,            ocr,            vf);
     REGISTER_FILTER(OCV,            ocv,            vf);
     REGISTER_FILTER(OVERLAY,        overlay,        vf);
     REGISTER_FILTER(OWDENOISE,      owdenoise,      vf);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR   1
+#define LIBAVFILTER_VERSION_MINOR   2
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \

libavfilter/vf_ocr.c

+/*
+ * Copyright (c) 2015 Paul B Mahol
+ *
+ * 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 <tesseract/capi.h>
+
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "formats.h"
+#include "internal.h"
+#include "video.h"
+
+typedef struct OCRContext {
+    const AVClass *class;
+
+    char *datapath;
+    char *language;
+    char *whitelist;
+    char *blacklist;
+
+    TessBaseAPI *tess;
+} OCRContext;
+
+#define OFFSET(x) offsetof(OCRContext, x)
+#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption ocr_options[] = {
+    { "datapath",  "set datapath",            OFFSET(datapath),  AV_OPT_TYPE_STRING, {.str=NULL},  0, 0, FLAGS },
+    { "language",  "set language",            OFFSET(language),  AV_OPT_TYPE_STRING, {.str="eng"}, 0, 0, FLAGS },
+    { "whitelist", "set character whitelist", OFFSET(whitelist), AV_OPT_TYPE_STRING, {.str="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ.:;,-+_!?\"'[]{}()<>|/\\=*&%$#@!~"}, 0, 0, FLAGS },
+    { "blacklist", "set character blacklist", OFFSET(blacklist), AV_OPT_TYPE_STRING, {.str=""},    0, 0, FLAGS },
+    { NULL }
+};
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    OCRContext *s = ctx->priv;
+
+    s->tess = TessBaseAPICreate();
+    if (TessBaseAPIInit3(s->tess, s->datapath, s->language) == -1) {
+        av_log(ctx, AV_LOG_ERROR, "failed to init tesseract\n");
+        return AVERROR(EINVAL);
+    }
+
+    if (!TessBaseAPISetVariable(s->tess, "tessedit_char_whitelist", s->whitelist)) {
+        av_log(ctx, AV_LOG_ERROR, "failed to set whitelist\n");
+        return AVERROR(EINVAL);
+    }
+
+    if (!TessBaseAPISetVariable(s->tess, "tessedit_char_blacklist", s->blacklist)) {
+        av_log(ctx, AV_LOG_ERROR, "failed to set blacklist\n");
+        return AVERROR(EINVAL);
+    }
+
+    av_log(ctx, AV_LOG_DEBUG, "Tesseract version: %s\n", TessVersion());
+
+    return 0;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    static const enum AVPixelFormat pix_fmts[] = {
+        AV_PIX_FMT_GRAY8,
+        AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV411P,
+        AV_PIX_FMT_YUV420P, AV_PIX_FMT_YUV422P,
+        AV_PIX_FMT_YUV440P, AV_PIX_FMT_YUV444P,
+        AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_YUVJ422P,
+        AV_PIX_FMT_YUVJ440P, AV_PIX_FMT_YUVJ444P,
+        AV_PIX_FMT_YUVJ411P,
+        AV_PIX_FMT_YUVA444P, AV_PIX_FMT_YUVA422P, AV_PIX_FMT_YUVA420P,
+        AV_PIX_FMT_NONE
+    };
+
+    AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
+    if (!fmts_list)
+        return AVERROR(ENOMEM);
+    ff_set_common_formats(ctx, fmts_list);
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVDictionary **metadata = avpriv_frame_get_metadatap(in);
+    AVFilterContext *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    OCRContext *s = ctx->priv;
+    char *result;
+
+    result = TessBaseAPIRect(s->tess, in->data[0], 1,
+                             in->linesize[0], 0, 0, in->width, in->height);
+    av_dict_set(metadata, "lavfi.ocr.text", result, 0);
+    TessDeleteText(result);
+
+    return ff_filter_frame(outlink, in);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    OCRContext *s = ctx->priv;
+
+    TessBaseAPIEnd(s->tess);
+    TessBaseAPIDelete(s->tess);
+}
+
+AVFILTER_DEFINE_CLASS(ocr);
+
+static const AVFilterPad ocr_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad ocr_outputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_VIDEO,
+    },
+    { NULL }
+};
+
+AVFilter ff_vf_ocr = {
+    .name          = "ocr",
+    .description   = NULL_IF_CONFIG_SMALL("Optical Character Recognition."),
+    .priv_size     = sizeof(OCRContext),
+    .priv_class    = &ocr_class,
+    .query_formats = query_formats,
+    .init          = init,
+    .uninit        = uninit,
+    .inputs        = ocr_inputs,
+    .outputs       = ocr_outputs,
+};