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Rainbow in the Dark
Posted: Fri Mar 20, 2009 6:54 pm
by efe
It took me quite a while until I figured out the correct sort sequence of the pixels.
This was very helpful:
http://en.wikipedia.org/wiki/HSL_and_HS ... HSL_or_HSV 
Here is my Python Code:
Code: Select all
import Image
img = Image.open("rainbow.png")
pixel = img.load()
width,height = img.size
def sortkey(x):
r,g,b = x[0]/255.0, x[1]/255.0, x[2]/255.0
cmax = max ([r,g,b])
cmin = min ([r,g,b])
if cmax==r:
return (g-b)/(cmax-cmin)
elif cmax==g:
return 2.0+(b-r)/(cmax-cmin)
else: # cmax==b
return 4.0+(r-g)/(cmax-cmin)
for y in range(height):
pixellist = [pixel[x,y] for x in range(width)]
pixellist.sort(key=sortkey)
for p,i in map(None,pixellist,range(width)):
pixel[i,y] = p
img.show()
Posted: Fri Mar 20, 2009 8:22 pm
by teebee
This was very helpful for creating the challenge:
http://snurl.com/e88zm
Posted: Tue Dec 03, 2013 8:37 am
by TheBigBoss
Nice to see the intended final image from the Python code above.
I used a technique similar to other challenges. I created four images from the source using different transformations, flipped them if necessary and put them side to side. The result was at least readable.
Posted: Sun Jul 02, 2017 4:10 am
by Redford
Seems like I've found the solution in a similar way to TheBigBoss.
I wanted to test if there's something hidden in the pixels (treated as raw bytes), so I converted the image to BMP and looked at the image using trigram view in
Veles (a tool which I'm one of the devs). To my surprise, I found something which looked like letters:
Then I wrote a Python script to extract faces of the cube (only these with letters), merged them in Gimp and recovered the password.
I'm not sure why sorting pixels generated such properties, it's probably something related to how pixels containing FF byte were ordered.
More fancy images below
