Monday 24 February 2014

Image Quality Tool - Fool the Tool

Re-sized Images

An easy cheat for the Birding Image Quality Tool would be to take an image which scores poorly because of low pixel resolution and simply re-size it bigger.  Now all of a sudden it contains as many pixels as a much better resolved image.  

It is surprisingly difficult to detect such a simple cheat I have found.  You might assume the image would contain obvious duplicates of each pixel but this may not always be the case.  The image editing software may re-compress the image and re-touch its sharpness a bit, masking any obvious aliasing of pixels.

The best solution to avoid this is to ask the photographer to supply the original, unaltered JPEG, or ideally RAW format image if available.

I came across a really cool website while researching this question called

The website allows you to upload an image which it scans looking for evidence of image manipulation.  
Using this site I was able to detect an obvious difference between an image which I simply re-sized and re-saved compared to the original unaltered image so there are ways and means to detect a fraud.

However this is a a lot of effort to go to for typical birders or rarities committees.  One downside to simply re-sizing an image to beat the pixel resolution test is that the image will appear softer and more pixellated, plus more valuable data may have been lost to image compression.  I will look at the relative scoring of the resolution and focus tests again to try and compensate for someone trying to dupe the tool under these circumstances.

I now have a couple of tweaks to make so I will get on and have a go at REV. 1.2 of the tool.

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