[FFmpeg-devel] [Patch] vf_edgedetect: properly implement double_threshold()
Andriy Gelman
andriy.gelman at gmail.com
Mon Jun 22 08:35:33 EEST 2020
Hi Valery,
Thanks for the patch.
Please also update the fate test:
https://patchwork.ffmpeg.org/project/ffmpeg/patch/CAGTf1MnCX2JOO-VMTUCDKjCP76y5JsLnhubzat4MF48c2hfd6g@mail.gmail.com/
On Fri, 19. Jun 17:15, Valery Kot wrote:
> vf_edgedetect video filter implements Canny algorithm
> (https://en.wikipedia.org/wiki/Canny_edge_detector)
>
> Important part of this algo is the double threshold step: pixels above
> "high" threshold being kept, pixels below "low" threshold dropped,
> pixels in between kept if they are attached to "high" pixels.
>
> This is implemented in the double_threshold() function. However,
> condition to start checking attached pixels, as it is now and as it
> was in FFmpeg since 2012, only allows checking on the boundary, not
> inside the video. It is a very lucky coincidence that those boundary
> pixels are always 0, otherwise following lines would be reading
> outside of the buffer.
>
> As it is now, double_threshold() only implements "high" thresholding.
> As a result, edges are either noisy or fragmented, depending on "high"
> threshold selection; "low" threshold is simply ignored.
>
> Attached one char patch fixes this.
>
> Please review.
>
> Valery
> From b78f5960736de52d1c8e41bd598a465092c1de60 Mon Sep 17 00:00:00 2001
> From: vkot <valery.kot at kinetiq.tv>
> Date: Fri, 19 Jun 2020 16:57:13 +0200
> Subject: [PATCH] vf_edgedetect: properly implement double_threshold()
Add an avfilter/ prefix to the commit title.
>
> ---
> libavfilter/vf_edgedetect.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/libavfilter/vf_edgedetect.c b/libavfilter/vf_edgedetect.c
> index a5614ea63b..df8afbd532 100644
> --- a/libavfilter/vf_edgedetect.c
> +++ b/libavfilter/vf_edgedetect.c
> @@ -294,7 +294,7 @@ static void double_threshold(int low, int high, int w, int h,
> continue;
> }
>
> - if ((!i || i == w - 1 || !j || j == h - 1) &&
> + if (!(!i || i == w - 1 || !j || j == h - 1) &&
> src[i] > low &&
> (src[-src_linesize + i-1] > high ||
> src[-src_linesize + i ] > high ||
> --
> 2.26.2.windows.1
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
Thanks,
--
Andriy
More information about the ffmpeg-devel
mailing list