Wikipedia:Reference desk/Archives/Miscellaneous/2023 August 22

= August 22 =

How to cleanup Google-digitized image artifacts
There's an amazing archive of old Google-digitized images held by groups like HathiTrust. But as you can see from this example, many of them have some kind scanning artifact. What is the best way to remove these artifacts? I would like to upload these wonderful images to Commons. Viriditas (talk) 22:58, 22 August 2023 (UTC)
 * , I suggest that you ask at Graphics Lab. Editors skilled at improving images are active there. Cullen328 (talk) 23:18, 22 August 2023 (UTC)
 * Thank you! I will remove this post. Viriditas (talk) 23:25, 22 August 2023 (UTC)
 * Update, the graphics lab takes requests for specific images, they don't help you answer these types of questions. My guess is that this question has come up dozens of times before since it's an error unique to Google-digitized images, so maybe someone knows something. Viriditas (talk) 23:57, 22 August 2023 (UTC)
 * , perhaps you can submit a small sample, say three to five images, and if another editor succeeds in improving the image quality, discuss their techniques and tools with them. Cullen328 (talk) 00:02, 23 August 2023 (UTC)
 * That's a great idea. Now I know why they pay you the big bucks. Viriditas (talk) 00:03, 23 August 2023 (UTC)
 * Actually, I get paid in crappy virtual T-shirts. Cullen328 (talk) 00:04, 23 August 2023 (UTC)
 * Now you can retire (for a second time) and rest on your laurels. You've finally made it. Viriditas (talk) 00:08, 23 August 2023 (UTC)
 * Would you prefer Trump Bucks? You could become a Trumpillionaire! Clarityfiend (talk) 13:06, 23 August 2023 (UTC)


 * The latest WP:Signpost has a relevant article -- Verbarson talkedits 11:10, 23 August 2023 (UTC)

Pages 348, 350, 353, 355 and 357 of the given reference show very interesting full-tone images marred by an Aliasing pattern probably generated by mismatch of the Photogravure printing screen and the Google scanner grid. In principle the undesired pattern can be reduced by processing each digital image file with a two-dimensional bandstop filter. However this is difficult to apply because 1) a lack of existing tools so that new programming is called for, 2) the pattern frequency and orientation must be found for each image and 3) the degree of filtering must be adjusted by eye to minimise degradation (blurring) of the remaining image. Fast Design of 2-D Narrow Bandstop FIR Filters for Image Enhancement  offers a mathematical treatment but I have not yet seen a convincing demonstration of this kind of image restoration. Philvoids (talk) 11:32, 23 August 2023 (UTC)
 * when I used to use a scanner back in the early 2000s, the scanner software had a filter to remove moiré pattern artifacts. They looked very much like this. Viriditas (talk) 08:08, 24 August 2023 (UTC)
 * Software that controls the image scan process can reduce moiré artifacts by a strategy such as scan at 2X the desired resolution, apply a blur filter and finally resample to half size to get the desired image size. It's much more difficult to remove pattern artifacts after they have been added to an image. I doubt that Google would be inclined to redo their scan work but there is moiré avoiding advice here. Philvoids (talk) 09:17, 24 August 2023 (UTC)
 * I thought as much. Thank you for the education! Viriditas (talk) 09:21, 24 August 2023 (UTC)
 * See also . --Lambiam 21:29, 27 August 2023 (UTC)