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Re: [Openexr-devel] OpenEXR vs Raw images
From: |
Rod Bogart |
Subject: |
Re: [Openexr-devel] OpenEXR vs Raw images |
Date: |
Mon, 22 Dec 2003 12:33:35 -0800 |
User-agent: |
Mutt/1.2.5i |
On Mon, 22 Dec 2003, nkb wrote:
> I did a simple comparision. In terms of file size, for the same image,
> canon crw file size (in my example) is 4.7MB while openexr format with
> piz compression yields a result of 12.8MB.
The 3x size difference is because the CRW has only one channel, and the
OpenEXR has three. CRW uses a single value per pixel, with an assumed
layout (something like RGRGRGRGRG for even scanlines and GBGBGBGBGB for
odd scanlines). It is a mosaic sensor, stored in the CRW file. To make
an RGB for each pixel, there is a filtering step which blends neighboring
pixels together. After this step, you have three times as much data to
store in the output file.
RGB