Updated Aug 16, 2020 at 02:37AM EDT by ohmyjosh.

Added Jun 30, 2011 at 02:46PM EDT by Chris.

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Gmask is a computer program that masks images by scrambling pixels or applying a filter that can be later reversed back to the original image composition. Since its release in 1996, the application has been used to censor NSFW photographs before sharing them on forums and imageboards, or to create puzzle games for other members to solve.


Originally released in 1996 for Microsoft Windows 95, Gmask[1] allows its users to obscure images using a variety of effects, including spirals, vertical lines, photo negative, vertical glass and horizontal glass. The earliest archived Gmask post on 4chan[10] was submitted to a thread featuring the Flea Market Montgomery commercial in the /b/ (random) board on May 8th, 2008 (shown below).

>> □ Anonymous 05/08/08(Thu)00:53:28 No.66386100 File 1210222408127 ipg-(52 KB, 357x537, meko01. jpg) L gmasking in a epic thread


On April 14th, 2009, OwnedCore Forums[11] member Parod submitted a thread titled “Gmasking – Hidden Pictures!”, which invited readers to join in and submit their own Gmask images (shown below). Parod also provided a list of rules, specifying that participants could use up to four masks, work safe pictures only and should refrain from using images of popular memes.

DO NOT use more than 4 masks ( that means 4 button press – Pressing M- twice would count as 2. )
DO NOT use pictures that would be innapropriate to a family site. ( No porn / JB / CP )
DO NOT use highly known pictures or memes, it takes the fun out of discovering what's hidden behind it.
DO NOT mask the whole picture, chose something interesting to mask.
DO NOT use image flips after using M+, M- or FL as it makes it WAY too hard to solve.
DO NOT Use the CP ( passworded ) filter!
DO NOT Mask more than 1 area in a picture, or have 2 masks slighly overlap eachother.
DO use pictures of an appropriate size, not 2800×2000 or 12×12
DO make sure to post the original, unmasked picture with the solution ( in order and abvreviation ) before posting a new one.

On December 2nd, Flash Flash Revolution Forums[5] member Izzy submitted a Gmask puzzle thread, in which posters shared scrambled images and attempted to unmask them. On July 4th, 2010, David Icke Forums[4] member hollo submitted a similar Gmask puzzle thread, receiving 24 responses over the next year. On February 10th, 2011, the Gmask Repository[3] blog was launched, featuring various gmasked images of puzzles and adult-themed content. On September 29th, 2012, the Gmask Rumpus[9] blog was launched, which highlighted scrambled images of adult-themed content submitted by the readers. By the end of 2012, the blog had curated over 60 images.

Notable Examples


Search Interest

External References

[1] Homepage3.Nifty.Com via WaybackMachineGmask Download

[2] Encyclopedia Dramatica – Gmask

[3] Blogspot – Gmask Repository

[4] David Icke Official Forums via WaybackMachine – Gmask Thread

[5] FlashFlashRevolution – Gmask Thread

[6] Daemons Rings Forums – Gmask Thread

[7] MPGH – Gmask Anyone?

[8] Hongfire via WaybackMachine – Who Knows How To Use Gmask Thread

[9] Blogspot – Gmask Rumpus

[10] 4chan Archive – Its Just Like a Mini Mall

[11] Owned Core – Gmasking Hidden Pictures

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