Primatte chromakey technology

Source: Wikipedia, the free encyclopedia.

Primatte is a brand of

Eyeon Fusion
and several other compositing and editing software packages.

Example of chroma key effect.

Workflow

Primatte is usually activated on a foreground image with a person or other foreground object filmed or digitized against a solid colored background or backing screen; usually a

greenscreen
. The solid colored background area is removed and replaced with transparency. This allows the user to replace the solid colored background with a background image of their choice.

If the foreground object was filmed close to the backing screen or with less than ideal lighting conditions, the foreground object will usually have ‘spill’ somewhere on it. This is most common when filming blonde people against a blue or greenscreen as their translucent hair will absorb the backing screen color. Such ‘colorspill’ can be removed and replaced with several options to achieve a more realistic result.

Another problem is chromakeying images that were created on film stock is that some film stocks have a distinct ‘film grain’ to them. A large amount of film grain will often cause rough edges around the foreground object. Rough edges can be minimized to achieve a smoother transition between the edges of the ‘chroma keyed’ foreground object and the user selected background image.

History

The Primatte algorithm was created by Yasushi Mishima while working at

IMAGICA Corporation
in Tokyo, Japan in 1992. The basic algorithm utilized in Primatte was originally presented at the 8th NICOGRAPH Conference and the 23rd Imaging Technology Conference and a U.S. patent was granted in 1994.

It was initially released as a stand-alone product on

Macintosh
platforms.

The Algorithm

The Primatte chromakey algorithm is a method of color space

segmentation, where Primatte segments all the colors in the foreground image into one of four separate categories. The result is a 'spill suppressed' foreground image and a matte
which is used to apply the modified foreground to a suitable background.

Primatte works in 3D RGB color space. Here is a visual representation of the Primatte algorithm after an image has been processed.

3D Viewer Window

The user essentially creates three

polyhedrons
. These can be pictured as three globes (or polyhedrons or polys), one within the other, which share a common center point. The creation of these polyhedrons separates all possible foreground colors into one of four regions; inside the small polyhedron (1), between the small and medium polyhedrons (2), between the medium and the large polyhedrons (3) and outside the large polyhedron (4).

Primatte Algorithm Regions


See also

  • Computer Generated Imagery
  • Chroma key
  • Special Effects

External links