[FFmpeg-devel] Add alternative delogo algorithm for my donation

[uwe.freese at gmx.de]

Hello,

I would like that the delogo filter is improved by an alternative way of 
removing the logo. It's the "UGLARM" mode known from Virtual Dub's 
DeLogo filter and ffdshow.
I used it many years (under Windows), but now moving to Linux miss it 
using ffmpeg as encoding tool.

Since an ffmpeg developer can probably add the code in a fragment of the 
time and more consistently than it would take me to add it, I'd like to 
hire someone to do so.

The code is just ~50 lines, and already available in c for ffdshow. I'd 
donate 50 EUR (PayPal) for someone adding it - hopefully into the normal 
production code for everyone to use. :)
So if someone knows the delogo code / filter code and volunteers, let me 
know. :) I would be really glad if this could be done.


++ How does it work:

The algorith is called "UGLARM mode" and takes all pixels of the 1-pixel 
border of the box covering the logo into account to interpolate the 
inner pixels. Each pixel is taken into account according to an 
exponential value of the distance. The result is a more blurred and I 
find much more pleasing effect than the current xy-algorithm in 
ffmpgeg's delogo filter, which tends to show vertical and horizontal 
lines / crosses. Although the calculation takes more time than the 
xy-interpolation, this is absolutely not relevant compared to the video 
encoding time.

The code was impemented by myself ~15 years ago for the VirtualDub 
filter "LogoAway" by Chris Wojdon. It was taken over in the ffdshow 
Codec package for Windows.

"UGLARM" stands for "Uwe's Great LogoAway Remove Mode". :-) It was my 
not-so-serious answer to Chris about how we could name it. But the name 
was taken over in his filter and later ffdshow, where it's available 
until now.

++ How does it look:

See these examples:
http://www.fixya.com/support/r3995122-remove_logo_from_avi_mpg4_file_using
https://forum.videohelp.com/threads/260207-Remove-Spoilers-Logos-etc 
(search for "UGLARM" for the image).

++ Code to add:

I alreday took a look at the ffmpeg code and ffdshow code.
In ffdshow, you can find the functions in TimgFilterLogoaway.cpp:
https://sourceforge.net/p/ffdshow-tryout/code/HEAD/tree/trunk/src/imgFilters/TimgFilterLogoaway.cpp

In ffmpeg, it has to be added in libavfilter/vf_delogo.c, function 
apply_delogo.

Here's the relevant code to add (+ some config variable to set the mode 
I guess):

// Precalculate weights once.
void TimgFilterLogoaway::Tplane::calcUweWeightTable(int w, int h, int power)
{
     double e = 1.0 + (0.3 * power);
     int x;
     for (x = 0; x < w; x++)
         for (int y = 0; y < h; y++)
             if (x + y != 0) {
                 double d = pow(sqrt(double(x * x + y * y)), e);
                 uwetable[x + y * w] = 1.0 / d;
             } else {
                 uwetable[x + y * w] = 1.0;
             }

     for (x = 1; x < w - 1; x++)
         for (int y = 1; y < h - 1; y++) {
             double weightsum = 0;
             for (int bx = 0; bx < w; bx++) {
                 weightsum += uwetable[abs(bx - x) + y * w];
                 weightsum += uwetable[abs(bx - x) + abs(h - 1 - y) * w];
             }
             for (int by = 1; by < h - 1; by++) {
                 weightsum += uwetable[x + abs(by - y) * w];
                 weightsum += uwetable[abs(w - 1 - x) + abs(by - y) * w];
             }
             uweweightsum[y * w + x] = weightsum;
         }
}

// apply filter
void TimgFilterLogoaway::Tplane::uwe(const TlogoawaySettings *cfg)
{
     if (!uwetable) {
         uwetable = (double*)aligned_malloc(w * h * sizeof(double));
         uweweightsum = (double*)aligned_malloc(w * h * sizeof(double));
         calcUweWeightTable(w, h, cfg->blur);
     }

     for (int x = 1; x < w - 1; x++)
         for (int y = 1; y < h - 1; y++) {
             double r = 0;
             const unsigned char *lineN = bordn, *lineS = bords;
             for (int bx = 0; bx < w; bx++) {
                 r += lineN[bx] * uwetable[abs(bx - x) + y * w];
                 r += lineS[bx] * uwetable[abs(bx - x) + abs(h - 1 - y) 
* w];
             }
             const unsigned char *lineW = bordw, *lineE = borde;
             for (int by = 1; by < h - 1; by++) {
                 r += lineW[by] * uwetable[x + abs(by - y) * w];
                 r += lineE[by] * uwetable[abs(w - 1 - x) + abs(by - y) 
* w];
             }
             logotempdata[y * logotempstride + x] = uint8_t(r / 
uweweightsum[y * w + x]);
         }

}


Regards,
Uwe