[FFmpeg-devel] [PATCH V3] lavf/vf_ocr: add subregion support

[Steven Liu]

> 2021年6月18日 下午11:56，Lingjiang Fang <vacingfang at foxmail.com> 写道：
> 
> 
> fix doc errors, ping for review, thanks :)
> ---
> doc/filters.texi     |  8 ++++++++
> libavfilter/vf_ocr.c | 35 ++++++++++++++++++++++++++++++++++-
> 2 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index da8f7d7726..041fd28c57 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -15451,6 +15451,14 @@ Set character whitelist.
> 
> @item blacklist
> Set character blacklist.
> +
> + at item x, y
> +Set top-left corner of the subregion, in pixels, default is (0,0).
> +
> + at item w, h
> +Set width and height of the subregion, in pixels,
> +default is the bottom-right part from given top-left corner.
> +
> @end table
> 
> The filter exports recognized text as the frame metadata @code{lavfi.ocr.text}.
> diff --git a/libavfilter/vf_ocr.c b/libavfilter/vf_ocr.c
> index 6de474025a..e96dce2d87 100644
> --- a/libavfilter/vf_ocr.c
> +++ b/libavfilter/vf_ocr.c
> @@ -33,6 +33,8 @@ typedef struct OCRContext {
>     char *language;
>     char *whitelist;
>     char *blacklist;
> +    int x, y;
> +    int w, h;
> 
>     TessBaseAPI *tess;
> } OCRContext;
> @@ -45,6 +47,10 @@ static const AVOption ocr_options[] = {
>     { "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 },
> +    { "x",         "top x of sub region",     OFFSET(x),         AV_OPT_TYPE_INT,    {.i64=0},     0, INT_MAX, FLAGS },
> +    { "y",         "top y of sub region",     OFFSET(y),         AV_OPT_TYPE_INT,    {.i64=0},     0, INT_MAX, FLAGS },
> +    { "w",         "width of sub region",     OFFSET(w),         AV_OPT_TYPE_INT,    {.i64=0},     0, INT_MAX, FLAGS },
> +    { "h",         "height of sub region",    OFFSET(h),         AV_OPT_TYPE_INT,    {.i64=0},     0, INT_MAX, FLAGS },
>     { NULL }
> };
> 
> @@ -93,6 +99,21 @@ static int query_formats(AVFilterContext *ctx)
>     return ff_set_common_formats(ctx, fmts_list);
> }
> 
> +static void check_fix(int *x, int *y, int *w, int *h, int pic_w, int pic_h)
> +{
> +    // 0 <= x < pic_w
> +    if (*x >= pic_w)
> +        *x = 0;
> +    // 0 <= y < pic_h
> +    if (*y >= pic_h)
> +        *y = 0;
> +
> +    if (*w == 0 || *w + *x > pic_w)
> +        *w = pic_w - *x;
> +    if (*h == 0 || *h + *y > pic_h)
> +        *h = pic_h - *y;
> +}

What about check whether the logo area fits in the frame when .config_props = config_input ?
> +
> static int filter_frame(AVFilterLink *inlink, AVFrame *in)
> {
>     AVDictionary **metadata = &in->metadata;
> @@ -102,8 +123,20 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
>     char *result;
>     int *confs;
> 
> +    // TODO(vacing): support expression
> +    int x = s->x;
> +    int y = s->y;
> +    int w = s->w;
> +    int h = s->h;
> +    check_fix(&x, &y, &w, &h, in->width, in->height);
> +    if ( x != s->x || y != s->y  ||
> +        (s->w != 0 && w != s->w) || (s->h != 0 && h != s->h)) {
> +        av_log(s, AV_LOG_WARNING, "config error, subregion changed to x=%d, y=%d, w=%d, h=%d\n",
> +                                                                    x, y, w, h);
> +    }
> +
>     result = TessBaseAPIRect(s->tess, in->data[0], 1,
> -                             in->linesize[0], 0, 0, in->width, in->height);
> +                             in->linesize[0], x, y, w, h);
>     confs = TessBaseAPIAllWordConfidences(s->tess);
>     av_dict_set(metadata, "lavfi.ocr.text", result, 0);
>     for (int i = 0; confs[i] != -1; i++) {
> -- 
> 2.29.2
> 
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Thanks

Steven Liu