How to add transpranet background overlay on image (IplImage)

[xiaos]

Hi

@saudet , I try to add an overlay on iplimage, but I find overlay's background are black...

Any idea on how to solve this?

[saudet]

Do you have some code in C/C++ that does what you want?

[nicolake]

Hi, I think something like this : http://jepsonsblog.blogspot.com.ar/2012/10/overlay-transparent-image-in-opencv.html
it's possible?

[saudet]

Sure, what issues are you having doing the same in Java?

[nicolake]

for(int c = 0; opacity > 0 && c < output.channels(); ++c)
      {
        unsigned char foregroundPx =
          foreground.data[fY * foreground.step + fX * foreground.channels() + c];
        unsigned char backgroundPx =
          background.data[y * background.step + x * background.channels() + c];
        output.data[y*output.step + output.channels()*x + c] =
          backgroundPx * (1.-opacity) + foregroundPx * opacity;
      }

so far I could't translate those lines to test the function in java

[saudet]

You might want to try to use indexers: http://bytedeco.org/news/2014/12/23/third-release/
If you're still having issues understanding the code, you may also want to try and ask on Stack Overflow...

[saudet]

FYI, this is going to be much easier done using FFmpegFrameFilter with the overlay filter.