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What does straight Unmatted mean?
With straight (or unmatted) channels, transparency information is stored only in the alpha channel, not in any of the visible color channels. With straight channels, the results of transparency aren’t visible until the image is displayed [and interpreted correctly] in an application that supports straight channels.
What are Alpha colors?
The alpha channel is a color component that represents the degree of transparency (or opacity) of a color (i.e., the red, green and blue channels). It is used to determine how a pixel is rendered when blended with another.
What does the Alpha mean in premultiplied alpha?
With premultiplied alpha, the RGB components represent the emission of the object or pixel, and the alpha represents the occlusion. A more obvious advantage of this is that, in certain situations, it can save a subsequent multiplication (e.g. if the image is used many times during later compositing).
How is Alpha used in blending and compositing?
Alpha compositing, OpenGL blending and premultiplied alpha Image compositing is the process of combining one or more images into a single one. Compositing can be done in any number of ways, but a very common way of doing it is to use the alpha channel for blending. Here, alpha is loosely treated as opacity.
What is the difference between OpenGL blending and alpha compositing?
Alpha compositing, OpenGL blending and premultiplied alpha Alpha compositing, OpenGL blending and premultiplied alpha Image compositing is the process of combining one or more images into a single one. Compositing can be done in any number of ways, but a very common way of doing it is to use the alpha channel for blending.
How to recap premultiplied alpha in OpenGL?
To recap premultiplied alpha, our pipeline now operates like this: Render the premultiplied destination image onto the frame buffer. Render the premultiplied source image onto the frame buffer, with blending enabled, glBlendEquation (GL_FUNC_ADD), and glBlendFunc (GL_ONE, GL_ONE_MINUS_SRC_ALPHA).