[FFmpeg-devel] rectification filter
Paul B Mahol
onemda at gmail.com
Sun Aug 10 15:32:39 CEST 2014
On 8/9/14, Daniel Oberhoff <danieloberhoff at gmail.com> wrote:
>
> Am 08.08.2014 um 12:10 schrieb Michael Niedermayer <michaelni at gmx.at>:
>
>> On Thu, Aug 07, 2014 at 12:15:17AM +0200, Daniel Oberhoff wrote:
>>>
>>> Am 06.08.2014 um 12:12 schrieb Clement Boesch <u at pkh.me>:
>>>
>>>> On Sun, Aug 03, 2014 at 06:43:18PM +0200, Daniel Oberhoff wrote:
>>>> [...]
>>>>>>> +static av_cold int init(AVFilterContext *ctx)
>>>>>>> +{
>>>>>>> + return 0;
>>>>>>> +}
>>>>>>>
>>>>>>
>>>>>> please remove this one, there is no point in having code that does
>>>>>> nothing.
>>>>>>
>>>>>>> +
>>>>>>> +static av_cold void uninit(AVFilterContext *ctx)
>>>>>>> +{
>>>>>>> +}
>>>>>>> +
>>>>>>>
>>>>>>
>>>>>> ditto
>>>>>>
>>>>>
>>>>> Done thanks!
>>>>>
>>>>
>>>> Did you forget to attach the latest version of the patch or I missed it
>>>> somewhere in the thread?
>>>
>>> Sorry, think that day I wanted to add something else before resubmit, and
>>> then lost the time.
>>>
>>> Here also with changes suggested by timothy. Note that the
>>> parametrization is now traditional
>>> (i.e. k1 and k2 are zero-based, as for example in the opencv
>>> documentation about calibration).
>>>
>>> From b798b95eb2f9ec4043b2407970d351cc31dd9e6a Mon Sep 17 00:00:00 2001
>>> From: Daniel Oberhoff <daniel at danieloberhoff.de>
>>> Date: Mon, 28 Jul 2014 23:58:12 +0200
>>> Subject: [PATCH] avfilter: ported lenscorrection filter from frei0r
>>>
>>> ---
>>> Changelog | 2 +-
>>> MAINTAINERS | 1 +
>>> doc/filters.texi | 46 +++++++
>>> libavfilter/Makefile | 1 +
>>> libavfilter/allfilters.c | 1 +
>>> libavfilter/version.h | 4 +-
>>> libavfilter/vf_lenscorrection.c | 199
>>> +++++++++++++++++++++++++++
>>> tests/fate/filter-video.mak | 3 +
>>> tests/ref/fate/filter-pixfmts-lenscorrection | 8 ++
>>> 9 files changed, 262 insertions(+), 3 deletions(-)
>>> create mode 100644 libavfilter/vf_lenscorrection.c
>>> create mode 100644 tests/ref/fate/filter-pixfmts-lenscorrection
>>>
>>
>> This is missing a "Signed-off-by" from you
>
> So I what do I write there?
That is usually automatically done by git itself when you "git format-patch".
>
>>> diff --git a/Changelog b/Changelog
>>> index 25dd210..79393ce 100644
>>> --- a/Changelog
>>> +++ b/Changelog
>>> @@ -3,7 +3,7 @@ releases are sorted from youngest to oldest.
>>>
>>> version <next>:
>>> - Icecast protocol
>>> -
>>> +- ported lenscorrection filter from frei0r filter
>>>
>>> version 2.3:
>>> - AC3 fixed-point decoding
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index c383d3f..6948e22 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -354,6 +354,7 @@ Filters:
>>> vf_histogram.c Paul B Mahol
>>> vf_hqx.c Clement Boesch
>>> vf_il.c Paul B Mahol
>>> + vf_lenscorrection.c Daniel Oberhoff
>>> vf_mergeplanes.c Paul B Mahol
>>> vf_psnr.c Paul B Mahol
>>> vf_scale.c Michael Niedermayer
>>> diff --git a/doc/filters.texi b/doc/filters.texi
>>> index 86feebc..c4888d3 100644
>>> --- a/doc/filters.texi
>>> +++ b/doc/filters.texi
>>> @@ -5532,6 +5532,51 @@ kerndeint=map=1
>>> @end example
>>> @end itemize
>>>
>>> + at section lenscorrection
>>> +
>>> +Correct radial lens distortion
>>> +
>>> +This filter can be used to correct for radial distortion as can result
>>> from the use
>>> +of wide angle lenses, and thereby re-rectify the image. To find the
>>> right parameters
>>> +one can use tools available for example as part of opencv or simply
>>> trial-and-error.
>>> +To use opencv use the calibration sample (under samples/cpp) from the
>>> opencv sources
>>> +and extract the k1 and k2 coefficients from the resulting matrix.
>>> +
>>> +Note that effectively the same filter is available in the open-source
>>> tools Krita and
>>> +Digikam from the KDE project.
>>> +
>>> +In contrast to the @ref{vignette} filter, which can also be used to
>>> compensate lens errors,
>>> +this filter corrects the distortion of the image, whereas @ref{vignette}
>>> corrects the
>>> +brightness distribution, so you may want to use both filters together in
>>> certain
>>> +cases, though you will have to take care of ordering, i.e. whether
>>> vignetting should
>>> +be applied before or after lens correction.
>>> +
>>> + at subsection Options
>>> +
>>> +The filter accepts the following options:
>>> +
>>> + at table @option
>>> + at item cx
>>> +Relative x-coordinate of the focal point of the image, and thereby the
>>> center of the
>>> +distrortion. This value has a range [0,1] and is expressed as fractions
>>> of the image
>>> +width.
>>> + at item cy
>>> +Relative y-coordinate of the focal point of the image, and thereby the
>>> center of the
>>> +distrortion. This value has a range [0,1] and is expressed as fractions
>>> of the image
>>> +height.
>>> + at item k1
>>> +Coefficient of the quadratic correction term. 0.5 means no correction.
>>> + at item k2
>>> +Coefficient of the double quadratic correction term. 0.5 means no
>>> correction.
>>> + at end table
>>> +
>>> +The formula that generates the correction is:
>>> +
>>> + at var{r_src} = @var{r_tgt} * (1 + @var{k1} * (@var{r_tgt} / @var{r_0})^2
>>> + @var{k2} * (@var{r_tgt} / @var{r_0})^4)
>>> +
>>> +where @var{r_0} is halve of the image diagonal and @var{r_src} and
>>> @var{r_tgt} are the
>>> +distances from the focal point in the source and target images,
>>> respectively.
>>> +
>>> @anchor{lut3d}
>>> @section lut3d
>>>
>>> @@ -8744,6 +8789,7 @@ For example, to vertically flip a video with
>>> @command{ffmpeg}:
>>> ffmpeg -i in.avi -vf "vflip" out.avi
>>> @end example
>>>
>>> + at anchor{vignette}
>>> @section vignette
>>>
>>> Make or reverse a natural vignetting effect.
>>> diff --git a/libavfilter/Makefile b/libavfilter/Makefile
>>> index 0f54381..e9c8456 100644
>>> --- a/libavfilter/Makefile
>>> +++ b/libavfilter/Makefile
>>> @@ -138,6 +138,7 @@ OBJS-$(CONFIG_IL_FILTER) +=
>>> vf_il.o
>>> OBJS-$(CONFIG_INTERLACE_FILTER) += vf_interlace.o
>>> OBJS-$(CONFIG_INTERLEAVE_FILTER) += f_interleave.o
>>> OBJS-$(CONFIG_KERNDEINT_FILTER) += vf_kerndeint.o
>>> +OBJS-$(CONFIG_LENSCORRECTION_FILTER) += vf_lenscorrection.o
>>> OBJS-$(CONFIG_LUT3D_FILTER) += vf_lut3d.o
>>> OBJS-$(CONFIG_LUT_FILTER) += vf_lut.o
>>> OBJS-$(CONFIG_LUTRGB_FILTER) += vf_lut.o
>>> diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
>>> index 1877557..b1d6ff5 100644
>>> --- a/libavfilter/allfilters.c
>>> +++ b/libavfilter/allfilters.c
>>> @@ -156,6 +156,7 @@ void avfilter_register_all(void)
>>> REGISTER_FILTER(INTERLACE, interlace, vf);
>>> REGISTER_FILTER(INTERLEAVE, interleave, vf);
>>> REGISTER_FILTER(KERNDEINT, kerndeint, vf);
>>> + REGISTER_FILTER(LENSCORRECTION, lenscorrection, vf);
>>> REGISTER_FILTER(LUT3D, lut3d, vf);
>>> REGISTER_FILTER(LUT, lut, vf);
>>> REGISTER_FILTER(LUTRGB, lutrgb, vf);
>>> diff --git a/libavfilter/version.h b/libavfilter/version.h
>>> index 1a43dc5..47bac78 100644
>>> --- a/libavfilter/version.h
>>> +++ b/libavfilter/version.h
>>> @@ -30,8 +30,8 @@
>>> #include "libavutil/version.h"
>>>
>>> #define LIBAVFILTER_VERSION_MAJOR 4
>>> -#define LIBAVFILTER_VERSION_MINOR 11
>>> -#define LIBAVFILTER_VERSION_MICRO 102
>>> +#define LIBAVFILTER_VERSION_MINOR 12
>>> +#define LIBAVFILTER_VERSION_MICRO 100
>>>
>>> #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR,
>>> \
>>> LIBAVFILTER_VERSION_MINOR,
>>> \
>>> diff --git a/libavfilter/vf_lenscorrection.c
>>> b/libavfilter/vf_lenscorrection.c
>>> new file mode 100644
>>> index 0000000..c2346db
>>> --- /dev/null
>>> +++ b/libavfilter/vf_lenscorrection.c
>>> @@ -0,0 +1,199 @@
>>> +/*
>>> + * Copyright (C) 2007 Richard Spindler (author of frei0r plugin from
>>> which this was derived)
>>> + * Copyright (C) 2014 Daniel Oberhoff
>>> + *
>>> + * 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
>>> + */
>>> +
>>> +/**
>>> + * @file
>>> + * Lenscorrection filter, algorithm from the frei0r plugin with the same
>>> name
>>> +*/
>>> +#include <stdlib.h>
>>> +#include <math.h>
>>> +
>>> +#include "libavutil/opt.h"
>>> +#include "libavutil/intreadwrite.h"
>>> +#include "libavutil/pixdesc.h"
>>> +
>>> +#include "avfilter.h"
>>> +#include "internal.h"
>>> +#include "video.h"
>>> +
>>> +typedef struct LenscorrectionCtx {
>>> + const AVClass *av_class;
>>> + unsigned int width;
>>> + unsigned int height;
>>> + int hsub, vsub;
>>> + int nb_planes;
>>> + double cx, cy, k1, k2;
>>> +} LenscorrectionCtx;
>>> +
>>> +#define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
>>> +static const AVOption lenscorrection_options[] = {
>>> + { "cx", "set relative center x", offsetof(LenscorrectionCtx,
>>> cx), AV_OPT_TYPE_DOUBLE, {.dbl=0.5}, 0, 1, .flags=FLAGS },
>>> + { "cy", "set relative center y", offsetof(LenscorrectionCtx,
>>> cy), AV_OPT_TYPE_DOUBLE, {.dbl=0.5}, 0, 1, .flags=FLAGS },
>>> + { "k1", "set quadratic distortion factor",
>>> offsetof(LenscorrectionCtx, k1), AV_OPT_TYPE_DOUBLE, {.dbl=0.0}, -1, 1,
>>> .flags=FLAGS },
>>> + { "k2", "set double quadratic distortion factor",
>>> offsetof(LenscorrectionCtx, k2), AV_OPT_TYPE_DOUBLE, {.dbl=0.0}, -1, 1,
>>> .flags=FLAGS },
>>> + { NULL }
>>> +};
>>> +
>>> +AVFILTER_DEFINE_CLASS(lenscorrection);
>>> +
>>> +typedef struct ThreadData {
>>> + AVFrame *in, *out;
>>> + float w, h;
>>> + int plane;
>>> + float xcenter, ycenter;
>>> + float k1, k2;
>>> +} ThreadData;
>>> +
>>> +static int filter_slice(AVFilterContext *ctx, void *arg, int job, int
>>> nb_jobs)
>>> +{
>>> + ThreadData *td = (ThreadData*)arg;
>>> + AVFrame *in = td->in;
>>> + AVFrame *out = td->out;
>>> +
>>> + const float w = td->w, h = td->h;
>>> + const float xcenter = td->xcenter;
>>> + const float ycenter = td->ycenter;
>>> + const float r2inv = 4.0 / (w * w + h * h);
>>> + const float k1 = td->k1;
>>> + const float k2 = td->k2;
>>> + const int start = (h * job ) / nb_jobs;
>>> + const int end = (h * (job+1)) / nb_jobs;
>>> + const int plane = td->plane;
>>> + const int inlinesize = in->linesize[plane];
>>> + const int outlinesize = out->linesize[plane];
>>> + const uint8_t *indata = in->data[plane];
>>> + uint8_t *outrow = out->data[plane] + start * outlinesize;
>>> + int i;
>>> + for (i = start; i < end; i++, outrow += outlinesize) {
>>> + const float off_y = i - ycenter;
>>> + const float off_y2 = off_y * off_y;
>>> + uint8_t *out = outrow;
>>> + int j;
>>> + for (j = 0; j < w; j++) {
>>> + const float off_x = j - xcenter;
>>> + const float r2 = (off_x * off_x + off_y2) * r2inv;
>>> + const float radius_mult = 1.0f + r2 * k1 + r2 * r2 * k2;
>>> + const int x = xcenter + radius_mult * off_x + 0.5f;
>>> + const int y = ycenter + radius_mult * off_y + 0.5f;
>>> + const char isvalid = x > 0 && x < w - 1 && y > 0 && y < h -
>>> 1;
>>
>>> + *out++ = isvalid ? indata[y * inlinesize + x] : 0;
>>
>> IMHO "nearest neighbour" resampling isnt a reasonable choice, if
>> thats the only choice the user has.
>
> So you want me to add other methods? I found nearest neighbor sufficient for
> our needs and using other methods seemed to slow the code down too much for
> us, but if you think the filter is unfit for ffmpeg otherwise I will add
> other methods. Up to what order would you say resampling options are
> required?
It is not mandatory(but it would be nice) to add other methods to have
this filter included into libavfilter.
>
>> also md5 based regression tests and extensive use of floats are
>> unlikely to work together, different architectures/platforms or even
>> compiler versions might give you different results
>
> Sounds reasonable, so should I remove the tests then?
Yes.
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