Defkthon CTF - Misc 200 - Writeup

Given a text file of 61366 lines with each line having values similar to

255,255,255
255,255,255
237,130,48
215,140,82
255,243,207
255,251,237

etc.

I could identify that those were RGB values for an image.
So initially I tried to find the resolution of the pic that will multiply to 61366

 
for i in range(0,1000):
    for j in range(0,1000):
        if i*j==61366:
            print i,"*",j

I got the values to be 122 * 503, or 503*122.
So next thing was to create the image using Python Image Library. I used the CSV library to read from the input file. 

 
import Image
import csv
 
img = Image.new( 'RGB', (503,122), "black") # create a new black image
pixels = img.load() # create the pixel map
f=open('flag.txt','r')
reader = csv.reader(f, delimiter=',')
mycsv = list(reader)
k=0
for i in range(img.size[0]):    # for every pixel:
    for j in range(img.size[1]):
        pixels[i,j] = (int(mycsv[k][0]), int(mycsv[k][1]), int(mycsv[k][2])) # set the colour accordingly
        k=k+1
img.show()

and thus I got the image..

and thus the flag.