Color4

Color4 is a color representation that stores red, green, blue, and alpha components. The red, green, and blue channels define an opaque color, while the alpha channel encodes transparency. In computer graphics, Color4 is commonly used to pass color and opacity information through rendering pipelines, image editors, and shaders. The four components are usually named r, g, b, and a.

Component values can be stored in different numeric formats. Commonly, each channel is a floating-point value in the range 0.0 to 1.0, or an 8-bit integer in the range 0 to 255. The alpha channel ranges from fully transparent to fully opaque, with 0.0 to 1.0 or 0 to 255 correspondingly, though some APIs interpret alpha differently (premultiplied alpha is one such variant).

Color4 is often represented as a four-component vector, such as a vec4 in shading languages or a four-element structure in high-level APIs. A color might be constructed as Color4(r, g, b, a), with sample values like (0.5, 0.25, 0.75, 1.0) or (128, 64, 192, 255) in 8-bit form.

In rendering, alpha determines blending with underlying pixels: the output color is a blend of the foreground color and the destination color, weighted by alpha. This makes Color4 essential for translucency, antialiasing, and compositing. Some systems use premultiplied alpha, where the color channels are stored after being multiplied by alpha, which changes blending equations.

Color4 is closely associated with the RGBA color model and is subject to color space considerations such as linear versus sRGB encoding. Ordering (RGBA, ARGB, BGRA) varies by API and platform and must be matched to the receiving endpoint.