52 States in 8 Months

What Paul really saw…

Posted in Forreign blogs by Ulf on April 11, 2009

A long time ago Paul posted some pictures from Canada on his blog. This was one of them:image013
The picture reminded me of the flag of Dominica, some island nation in the Caribbean Sea which is always confused with the Dominican Republic. This is Dominica’s flag:
125px-flag_of_dominicasvgSo, what is wrong about Paul’s picture? The vertical river is missing, and the red reflection is in the wrong place. It turned out that these flaws were pretty easy to correct:
what_paul_really_saw

You’re not impressed? Okay, stop reading this blog post, there remainder will only tell you how I created this picture.

So, how did I do this? Well, creating the vertical river was easy. I just copied some piece of the horizontal river and mirrored/flipped it a few times such that one doesn’t see the pattern immediately. Moving the red reflection was a bit more challenging. At first I split Paul’s image into three channels, representing the red, green and blue parts:

red green blue

Then I calculated the difference between the red and the green channel (and I forced all negative values to zero):difference_red_green
Voilà, the red reflection was identified! The next steps were obvious: I amplified this difference a bit and then added it back to the red channel of the original picture. The next two pictures show the results with amplifications of γ=1.0 and γ=1.4:

rot_fast_weg rot_fast_weg

Finally, I added a new red reflection near the intersection of the two rivers by simply increasing the red channel, but this was once again a straight forward task after eliminating the first red reflection…

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One Response

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  1. tfrt said, on April 12, 2009 at 3:13 pm

    Hmm, some image processing.
    Seems interesting… you got mail ;-)


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