Using non-premultiplied TIFF files

Utilities for use with imported images

Using non-premultiplied TIFF files

TIFF files can have two styles of alpha handling: premultiplied, and non-premultiplied:

In a premultiplied TIFF, as the alpha value for a pixel is decreased (i.e. the pixel becomes more transparent), so the pixel's red, green and blue values are also decreased.

: You can see this in the Color Chooser's color well - as you make a color more transparent, less and less of the color remains in the color well, which finally becomes black and white. Regardless of which color you started with, none of it remains at full transparency.

: This makes it easier for the computer to composite TIFFs, as some of the arithmetic has already been done.

In a non-premultiplied TIFF, as a pixel's alpha value changes, its red, green and blue values remain the same.

: This makes it more work for the computer to composite TIFFs, as it has to do arithmetic at the compositing time which has already been done with a premultiplied TIFF.

Animo 2.0 normally uses premultiplied TIFF files; but it can also import non-premultiplied TIFF files that you have created in other applications. Such files must be correctly formatted for Animo 2.1 to recognize they are not pre-multiplied, and treat them appropriately.

Unfortunately, some other companies' applications fail to set the flag inside a TIFF file that marks it as non-premultiplied. The file looks like a premultiplied TIFF to Animo 2.0 (and to any other application!), and is imported as such. Consequently, the file may not look as expected. This is usually most noticeable at the edges of opaque sections of the image, which can look ragged and miscolored. To correct this, you must use a script we provide. Type:

set_needs_premultiply TIFF_filenames

This correctly flags the specified TIFF file(s), so Animo 2.0 then treats them properly.

Utilities for use with imported images

Using non-premultiplied TIFF files