Transparency

UNDER CONSTRUCTION. oh dear what is this mess.

Layer Transparency

Alpha channels

Many programs and programming languages will refer to a file format as "RGB" and "RGBA". You've read about how image formats store their colors as three separate channels, red, green and blue, but not you can add a fourth channel. The "Alpha" channel.

For many file formats this is where the actual transparency value of an image is stored.

The concept of an "alpha" channel can be a little hard to understand some times. This is because some programs, like Adobe Photoshop, make it seem as if the alpha channel of an image is saved like a "layer" would be instead of a color channel as it is in some other contexts.

Whether or not you'll actually have to define your transparency as an "alpha" channel depends on your requirements. To be honest the only time this author has had to use the "alpha" channel operations of Adobe Photoshop is when testing specific game engines. For most Graphic Design, Painting, and Web Design work you can probably use the terms "transparency" and "alpha" almost interchangeably.

Masks

The concept of masking will vary in use between programs and will be discussed more in depth in the various discipline sections. The general idea that you should internalize early on is the basic definition of a mask.

A mask is an image, either vector or greyscale raster, that dictates the transparency of another image.

You will immediately wonder what the difference is between a Mask and basic Transparency of an image.

Typically the transparent part of an image in a compressed format is not saved. The "clear" parts of a png or gif for instance are usually discarded to save space. To "Mask" part of an image typically refers to a non-destructive use of transparency in an editing environment.

In other words it allows you to define transparency temporarily, before you make the change permanent, and usually in the authoring environment before a compressed version of your media is saved (and unseen areas discarded).

These words are the same for both still images and video alike. In Adobe Photoshop you might use a mask to hide parts of an image that you wish to bring back, and similarly in something like Premiere Pro or After Effects you might wish to temporarily hide parts of a movie clip in your raw project environment before the final cut is exported as a single video file.