Re: [Openexr-devel] B44 question

[Florian Kainz]

Hai,

the B44 compression rate is fixed; it does not depend on image content.
If you store the pixels as RGB data, the compression rate for the raw
pixels is 32:14 (approximately 2.28:1).  If you store the pixels as
luminance/chroma data, the compression rate is 32:7 (approximately 4.57:1).
In addition to the pixels, the file contains header data and some padding,
so the overall compression rate will be slightly less.

Since the compression rate is fixed, the easiest way to determine the
size of a file with given dimensions, is to compress one image; other
images will have the same size.

I don't have an exact formula for the size of B44-compressed files,
but if necessary, we can probably work it out.

Florian



Hai Nguyen wrote:
> Hi,
>
> I am wondering if there was a formula of some type of find the maximum 
> size of a B44 compressed image
> give its dimensions? I briefly looked through the header files but I 
> couldn't find what type the final compressed
> data is stored in.
>
> Thanks,
> - Hai
>
>
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