TIFF Transparency


Today’s Question: How do you get transparency in a TIFF file?

Tim’s Quick Answer: Transparency in a TIFF image is achieved by either erasing pixels or (preferably) by using a layer mask to hide pixels. However, most applications will not automatically reflect that transparency.

More Detail: This question was something of a follow-up to a question (or two) that previously addressed the PNG (Portable Network Graphics) file format, which supports transparency. What transparency means in the context of a PNG image is that most applications will actually support the transparency, so that whatever is “behind” the image will show through in transparent areas. For example, PNG images with transparency are often used on a website for situations where you want to be able to change the background color of the website without having to modify the PNG image.

For TIFF images the situation is slightly different, since TIFF images are typically used for scenarios that are different from the typical scenarios for PNG images. For example, while PNG images are often used for websites, TIFF images are typically used for printing and other situations that tend to call for larger overall image sizes (and in some cases more advanced features).

For some applications (such as page layout applications) a saved selection (or other layer mask or alpha channel) in a TIFF image can automatically be used as a mask for the image. In other words, even if the master image actually contains a full rectangular arrangement of pixels, an alpha channel can be used so that only the area defined by a saved selection or layer mask is shown when the image is placed in a document.

So, if you want to preserve transparency when saving a TIFF image, you really just need to preserve any layer masks, saved selections, and alpha channels that were used to create that transparency in Photoshop. Just keep in mind that only certain applications will actually present the image with that transparency, since the image is at that point a layered image that for the most part can be thought of as a Photoshop-only image file.