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TiffEncoderOptions.AlphaPremultiplied Property

Gets/sets the value that determines whether to premultiply image with alpha channel during image encoding or not.

Namespace: Aurigma.GraphicsMill.Codecs
Assembly: Aurigma.GraphicsMill (in Aurigma.GraphicsMill.dll)


Visual Basic
Public Property AlphaPremultiplied As Boolean
public bool AlphaPremultiplied { get; set; }

Property Value

The value which determines whether to premultiply color channels of each pixel with corresponding alpha channel during image encoding or not.


The value of this property has meaning only when saving image with alpha channel.

TIFF specification defines two ways of alpha channel encoding.

  • The first is so called "unassociated alpha" - when content of the alpha channel is simply stored along with color channels of the image. This is default behaviour.
  • The second way is to store image with "associated" alpha channel. This way implies that not only alpha channel itself will be encoded into the file, but also color channels of each pixel will be premultiplied with the corresponding alpha channel value.

You should use TIFF files with associated alpha if you have software which gain some benefit from them (for example, unassociated alpha channel will be shown as separate channel in Adobe® Photoshop®, while image with associated alpha will be shown as image with transparency). But you should take into account that premultiplying process slows down encoding and introduces rounding error. So you should not set this property to true without reason.

There is no difference for you between files with "associated" and "unassociated" alpha if you process them with Graphics Mill for .NET. TiffReader class implementation takes into account this option during image decoding and performs demultiplication if necessary. So you will always get usual Bitmap object with "unassociated" alpha.

See Also