Is PNG alpha Premultiplied?

PNG uses “unassociated” or “non-premultiplied” alpha so that images with separate transparency masks can be stored losslessly.

What is Alpha Premultiplied?

“Premultiplied alpha” or a “premultiplied image” means that the color image was masked (multiplied) by its own alpha channel; it has already been masked. Images with hand-painted masks are normally saved unmasked.

What is difference between straight alpha and Premultiplied?

In straight alpha, the RGB channels are left untouched and aren’t matted or premultiplied with a specified color. When ignoring the image’s alpha-channel, the image will not look correct and have rough edges and dots all over the place. This can be surprising for people who do not know what straight alpha is.

Does PNG support 16 bit?

As with RGB and gray+alpha, PNG supports 8 and 16 bits per sample for RGBA or 32 and 64 bits per pixel, respectively. Pixels are always stored in RGBA order, and the alpha channel is not premultiplied.

Can PNG support 16 bit?

RGB. RGB (truecolor) PNGs, like grayscale with alpha, are supported in only two depths: 8 and 16 bits per sample, corresponding to 24 and 48 bits per pixel. This is the image type most commonly used by image-editing applications like Adobe Photoshop.

How does alpha value work?

The alpha channel controls the transparency or opacity of a color. Its value can be represented as a real value, a percentage, or an integer: full transparency is 0.0, 0% or 0, whereas full opacity is 1.0, 100% or 255, respectively.

How does alpha transparency work?

Alpha transparency is a way to support gradations of opacity on a continuum. Values between zero (0) and one (1) allow some of the background to “show through” and “mix” with that color. Values closer to zero (0) show more background, and values closer to one (1) show less background.

What alpha value is transparent?

0 to 1
When alpha compositing is in use, each pixel has an additional numeric value stored in its alpha channel, with a value ranging from 0 to 1. A value of 0 means that the pixel is fully transparent and the color in the pixel beneath will show through.

What does premultiplied alpha mean in image processing?

“Premultiplied alpha” or a “premultiplied image” means that the color image was masked (multiplied) by its own alpha channel; it has already been masked. Images with hand-painted masks are normally saved unmasked. (Unmasked images usually go by one of the names “straight alpha”, “unpremultiplied alpha”, or “unassociated alpha”.)

What is premultiplied and how does it work?

Premultiplied is pre-masked. To use the mask, to actually apply it, your software multiplies the image and the mask together. The result is an image that has been masked over black. Notice how this was the first step of compositing from above.

Why do renderers produce pre-masked (premultiplied) images?

So renderers produce pre-masked (premultiplied) images for the exact same reason compositors do – they have to do masking along the way, and once you’ve started masking and layering, everything comes out masked. Just like with compositors, many renderers have a setting that will allow you to unmask the output image.