What Is Alpha Gradient?
The red, green and blue color space is the most commonly used in computer graphics and imaging. Each color is represented by its own channel, the combination of which produces the full-color images we see onscreen. Some graphics editors, however, support an augmented version of the RGB color space called RGBA, where the “A” represents something known as the alpha channel.
Other People Are Reading
-
The Alpha Channel
-
Basically, the alpha channel in an RGBA-based image contains the image’s transparency information. A pixel with an opacity value of zero percent in the alpha channel is totally transparent; a pixel with an opacity value of 100 percent is fully opaque. The alpha channel is used to blend two or more images by manipulating the opacity values in their respective alpha channels, making it possible to blend the images without editing their red, green and blue channels directly. The alpha channel is grayscale. By painting black onto the alpha channel in an application like Adobe Photoshop, for example, the corresponding parts of the image’s red, green and blue channels are rendered translucent, while painting white onto the alpha channel makes the corresponding areas fully opaque. Painting shades of gray into the alpha channel produces relative degrees of translucency.
Gradients in the Alpha Channel
-
In computer graphics, a gradient is a smooth transition between two or more colors wherein every hue between the extremes is represented. An alpha gradient is a white to black gradient applied to the alpha channel of an image. For example, creating a white to black gradient in an image’s alpha channel results in an image that smoothly fades between complete opacity and complete transparency. If the graphics editor being used supports layers, other images and color fills on the layers below this image show through in the translucent and transparent areas.
-
Possible Uses of an Alpha Gradient
-
Alpha gradients are often used to blend two, similar images in such a way that it’s nearly impossible to tell that two distinct images were used. For example, an astrophotographer might use an alpha gradient to blend two, discrete images of the night sky to produce a much wider-scale overall image. Alpha gradients are also often used in the production of print advertisements. An alpha gradient is used to gradually fade an image of a given product or scene, leaving a blank area in which text and other elements can be placed.
Applications and File Formats
-
As of November 2011, most current versions of high-profile imaging applications like Adobe Photoshop, Adobe Flash and Corel Painter, among others, include the ability to apply an alpha gradient to an image. In these contexts, the alpha gradient is often referred to as a “gradient mask.” Several consumer-level applications also support alpha channel editing and gradients as well. Not all image file formats support alpha channels, however. The TIFF, PNG and TGS formats support them, as well as the various proprietary formats associated with compatible editors, such as Photoshop’s PSD format. The GIF format also supports the alpha channel, but cannot utilize alpha gradients — each pixel in a GIF image’s alpha channel can only be fully transparent or fully opaque.
-
Resources
- Photo Credit David De Lossy/Photodisc/Getty Images
