A Photoshop contest, or sometimes photochop contest, is an online game, in which a website or user of an Internet forum will post a starting image — usually a photograph — and ask others to manipulate the image using some kind of graphics editing software, such as Photoshop, Corel Photopaint, The GIMP, Paint Shop Pro, Paint.NET or Microsoft Paint.
While Photoshop is the industry standard image editing program, Adobe discourages use of "Photoshop" to refer to anything other than Adobe's photo editing software, to prevent its trademark from becoming a genericized trademark.
A large part of the humor in many of these contests involves the use of internet memes.
Such contests are nowadays finding increasing participations in many blogs. A more "underground" variety of these image manipulation jokes involves the blending of celebrity faces with nude or pornographic images, often combined with references to movies, music, magazines and other forms of related popular culture.
Photoshop tennis 
Photoshop tennis (also known as Photoshop Pong or Photoshop battle (similar in its function to a "DJ battle" in hip hop music)) is a game played through sequential alternating photoshopping of an image. Photoshop tennis originated in graphics-related internet forums in the late-1990s/early-2000s, and shares an earlier history with online image games such as SITO's "PANIC" (started January, 1994). The game was made popular by art director Jim Coudal in 2001 as "Photoshop Tennis". The matches on coudal.com have since been renamed Layer Tennis, as they are no longer restricted to the use of Adobe Photoshop.
Each match of Photoshop tennis is generally played with two competing players. The players pick a starting image, or one is "served" by a player, then another player makes some sort of alteration to the image in any chosen image editor (matches are not exclusive to Adobe Photoshop). He or she then sends that altered image to the other player or players, usually via e-mail or by posting the image to a Photoshop tennis forum, who then edits that image and sends it back to the first player. This process goes back and forth until a predetermined number of rounds have elapsed, or the players otherwise wish to end the game. When the final round is over, there may be an independent judge who determines who has played the best shots, and declares that person the winner, or players may play without a clear winner. Sometimes extra rules can be enforced, such as sticking to one particular software package, or keeping to a particular theme.
A landscape photo composited and manipulated in Photoshop.
Photos composited and manipulated in Photoshop.
See also 
- Adobe Photoshop
- E-mail art
- Photo editing
- Something Awful's "Photoshop Phriday"
- SITO Panic and Photoshop Tennis
- Schreve, Jenn (2001-09-27). "Anyone for Photoshop Tennis?". Wired News. Retrieved 2007-10-27.
- Coudal Partners' Layer Tennis
- StreetFire Photochops
- Something Awful's Photoshop Phriday feature
- Photoshop contests