*This is a short summary of the full write-up at<https://smyghalloumi.se/posts/2018-11-01-seccon2018-qr.html>.*
After analyzing the problem one can see that we need to provide theweb service with a single image that produces at least two valid QRcodes with different results under the resizing sequence500→250→100→50.
Since the service is using the `NEAREST` operation, it is enough tofind the pixels from the original image that remain after resizing.
A simple test produces the pixels with indices `(10i + 7, 10j +7)`. So in order to create our image we need to overlay every pixelfrom one image into the above indices of the second image:
```im1[7::10, 7::10] = im2```
Uploading the resulting image to the service gives us back the flag.