Halo (photo editor)

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Halo effect

A halo is a (usually unwanted) effect in digital image processing ("halo" around the image object).

Emergence

It occurs when there is a color transition to the background in an object due to antialiasing and the background is replaced. This often happens in the following cases:

  • In GIF images, the background is defined as transparent, but the transition to the background is not, as there is no graduated transparency in this format. If the image is displayed on a web page against a different background, the halo effect occurs.
  • If you cut out such objects with image processing software and insert them into other images, the same effect occurs.

remedy

The problem can be avoided if the data format supports antialiasing through different levels of transparency or an alpha channel . If you work with vector graphics and only convert the image to a raster graphic after replacing the background , the problem does not arise either. This is not possible with digital photos as they are only available as raster graphics.

Anti-aliasing under the microscope
Halo effect under the magnifying glass