Timeline for What aspects of image preparation workflows can lead to accidents like Boris Johnson's No. 10 tweet's 'hidden message'?
Current License: CC BY-SA 4.0
38 events
| when toggle format | what | by | license | comment | |
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| Dec 24, 2021 at 14:23 | vote | accept | uhoh | ||
| Nov 14, 2020 at 3:25 | comment | added | David Waterworth | I think the answer to why you'd print an image, scan it and tweet it could conceivably be the person who tweeted the image only had access to a printed copy and not the digital original? | |
| Nov 13, 2020 at 21:31 | comment | added | Asteroids With Wings | @Andrei Not really. Those are two completely unrelated and different things. There are sensible reasons people upload images with text on to Twitter (formatting control, mainly). Doing a completely useless thing that takes loads of time and would ruin the quality of the image is incomparable. | |
| Nov 13, 2020 at 16:27 | comment | added | Andrei | @IMil While I agree that this explanation is not the best fitting, but your argument is also poor. The answer to who "would print an image and then scan it to use in a tweet?" is whoever tweets an image of some text on a text sharing platform. | |
| Nov 13, 2020 at 5:40 | comment | added | uhoh | @user10216038 dunno, I think my pens are talking to each other when I sleep, so I've moved them to separate pocket protectors. | |
| Nov 12, 2020 at 9:04 | comment | added | Chris H | ... If I left click and save image on my phone (Firefox for Android) over WiFi or 4G I get a 2048x1152px image, 149kB. Flood fill reveals hidden text. | |
| Nov 12, 2020 at 8:56 | comment | added | Chris H | unfortunately (in this case, but a very good idea overall) there's minimal EXIF info in JPGs downloaded from twitter | |
| Nov 12, 2020 at 8:55 | comment | added | Chris H | Another data point: Twitter serves image files based on context. If I right click on the image in the tweet and "save image as" in Firefox on Linux, i.e. desktop, I get a 680x383px image of 39kB; bucket fill, threshold 0 doesn't work (it shows something that might be parts of letters, but there's a region all round the white text that's lighter than background & dominated by jpg compression artifacts). If I left click on the image, I go to twitter.com/BorisJohnson/status/1325133262075940864/photo/1 which downloads as 4096x2304px, 378kB, reveals "Trump". File names are identical | |
| Nov 12, 2020 at 8:44 | comment | added | Chris H | as @AlanBirtles says - are you perhaps downloading over a mobile ISP? I've had trouble with O2 (a few years back) recompressing JPGs so map text wasn't legible. But twitter should always be https | |
| Nov 11, 2020 at 23:28 | comment | added | IMil | Sorry, but this explanation is ridiculous. Who would print an image and then scan it to use in a tweet? Even ignoring the highly incredible process, this would inevitably produce image distortions, which are not visible in the image. | |
| Nov 11, 2020 at 20:05 | comment | added | ManfP | I think this makes some assumptions that are a priori pretty unlikely: This would have to be a pretty high-quality print and scan (in terms of resolution+smoothness of the color), but yet low-quality enough so that there is text bleed that can easily seen by eye alone (but only at limited locations, with smooth and gradient-like edges). jkej's answer seems way more likely to me | |
| Nov 11, 2020 at 18:36 | comment | added | jkej | Printing and scanning a picture to post it on Twitter would be magnitudes more insane than directly creating a digital image with slightly higher resolution than needed. | |
| Nov 11, 2020 at 18:06 | comment | added | user10216038 | @Ahmed Tawfik - It used to be standard security policy to require printing 3 blank pages before using a classified printer to print unclassified. The original intent was to prevent bleed over like this. Of course like many governmental guides, the purpose was lost to blind rules resulting in imposing the same restrictions on ink-jet printers and labeling toner cartridges as classified and unclassified. It was easier to follow procedure than explain that a box of black dust doesn't store information anymore than a ballpoint pen remembers writing classified sentences. | |
| Nov 11, 2020 at 17:56 | comment | added | user10216038 | The image size of 4096x2304 is yet another indication that this was scanned paper. A direct digital image created that big for a Twitter post would be insane. | |
| Nov 11, 2020 at 17:08 | comment | added | Alan Birtles | maybe your web browser/ISP is recompressing the image before you download it? | |
| Nov 11, 2020 at 16:56 | comment | added | Tristan | curiouser and curiouser | |
| Nov 11, 2020 at 16:41 | comment | added | jkej | @Tristan But I have been working on such a large file all along and the background seems to be solid. | |
| Nov 11, 2020 at 16:39 | comment | added | Tristan | ah interesting. It's possible we are accessing the image after some sort of downscaling by twitter. If it is 4k then what we're seeing would be averaging over any noise you've got pretty well so it makes sense that we'd see a solid background | |
| Nov 11, 2020 at 16:39 | comment | added | jkej | @user10216038 Yes, that's the resolution of my image too. The file size is 368 KB (377 707 bytes). | |
| Nov 11, 2020 at 16:35 | comment | added | jkej | @user10216038 Are you doing something special to look at the "native file". I just open the file in GIMP. I manage to fill with 0 threshold. | |
| Nov 11, 2020 at 16:35 | comment | added | user10216038 | @jkej - The native file is 4096x2304. Which is a ludicrously large tweet image. | |
| Nov 11, 2020 at 16:29 | comment | added | user10216038 | @Tristan - Ijust pulled down the image again and used fill with 0 threshold, it did not fill. Using a threshold of 1 filled most and illuminated the hidden text. I believe that you are not looking at the native file. | |
| Nov 11, 2020 at 16:28 | comment | added | jkej | @user10216038 Yes, that appears to be the same image. Eventually you get to the same URL either way. Could they have changed the picture since you downloaded it? Could you upload the original that you have where the background is not uniform? | |
| Nov 11, 2020 at 16:19 | comment | added | Tristan | @user10216038 I agree with jkej, using a fill with 0 threshold, so it only fills identical colours, and the original photo, all the background apart from the visible text is filled in, suggesting it is a single colour. Something weird seems to have happened between the server and the tool you're using to look at it | |
| Nov 11, 2020 at 16:18 | comment | added | user10216038 | @jkej - The image I used is: twitter.com/BorisJohnson/status/1325133262075940864/photo/1 which I got to by following the Guido Fawkes Article then selecting the tweeted link and finally the actual tweet. | |
| Nov 11, 2020 at 16:11 | comment | added | jkej | @user10216038 Do you have a different original image than the rest of us? I have used the one Alan Birtles linked to. In that image the background certainly is a solid color. I have used the color picker in GIMP and the background color is #231F20 everywhere. | |
| Nov 11, 2020 at 16:02 | comment | added | user10216038 | @Alan Birtles - The background color is NOT a solid color. You can see this readily in GIMP by using the color picker at various points on the background and you will see it change. What's more, if you zoom to 400 or 800 percent you can readily see the lighter hidden text. | |
| Nov 11, 2020 at 14:01 | comment | added | Tristan | The text is easily revealable using a naive fill tool (i.e. one that only replaces the exact colour you click on). This replaces the background, but leaves behind the incorrect text, and a couple of jpg artifacts. This is not the behaviour you'd expect if @user10216038 had the right solution, and fits that suggested below much better | |
| Nov 11, 2020 at 13:58 | comment | added | Chris H | Similarly I don't see noise, only jpg artifacts (and some anti-aliasing effects) around the letters i.e. the background is pure #231F20 except near the letters | |
| Nov 11, 2020 at 13:55 | comment | added | John Dvorak | @AlanBirtles that's because they have a camera app preinstalled on their phone but their bluetooth isn't currently working and the corporate firewall doesn't allow word documents over the internal network... and they couldn't have taken a photo of the screen because it's one of those places that use a CRT. It might sound facetious but it's entirely plausible. | |
| Nov 11, 2020 at 13:39 | comment | added | Alan Birtles | @AhmedTawfik I'm not sure that in reality left over toner would leave a mark which is simultaneously not visible to the naked eye on the page, not visible in the scan/photograph and retrievable from the image. Even if it was possible why would anybody print something out just to take a picture of it? | |
| Nov 11, 2020 at 13:26 | comment | added | jkej | The noise in the image you posted is most probably an artifact of your equalizing algorithm. It certainly isn't there in the original. More importantly, the "hidden message" is brighter than the background. Surely, remaining toner from the last print could only have made the print darker? | |
| Nov 11, 2020 at 11:27 | comment | added | Ahmed Tawfik | Information leakage of this sort is terrifying. I can easily imagine national secrets having been printed on the printer instead, and therefore accidentally making to the Internet! | |
| Nov 11, 2020 at 11:16 | comment | added | Alan Birtles | The background of the original image is a solid colour as far as I can tell, not sure where the noisy background is coming from in your image | |
| Nov 11, 2020 at 9:22 | comment | added | uhoh | (not "pure color" I suppose I mean each toner color (y, m c)) | |
| Nov 11, 2020 at 7:40 | comment | added | uhoh |
Thanks! This is not what I expected but it turns out to be far more interesting. A quick check of correlation coefficients between colors for the "blank"100,000 pixel noisy area in the middle of your image with np.corrcoef(r, g) shows roughly a 0.8 correlation factor between any two colors, i.sstatic.net/5uI6e.png I suppose that doesn't mean anything conclusive without knowing more about the toner particle size, pixel size and focus, but it seems consistent with these being subtractive colors and therefore each pure color exciting two of the three RGB channels of the camera.
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| Nov 11, 2020 at 3:55 | history | edited | user10216038 | CC BY-SA 4.0 |
deleted 1 character in body
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| Nov 11, 2020 at 3:48 | history | answered | user10216038 | CC BY-SA 4.0 |
