Article View: comp.graphics.avs
Article #227read image Endian questions
From: Allen V. Schiano
Date: Wed, 16 Dec 1992 00:59
Date: Wed, 16 Dec 1992 00:59
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1894 bytes
Given that we have been having a lot of fun with this recently, I thought it would be a good time to ask the AVS community and AVS designers about how AVS reads images, i.e., *.x files. We've noticed that on our DEC 5200s running AVS, that the form of the various .x files in /usr/avs/data/image are often different. In particular, the digital.x and the avs.x, seem to have their bytes flipped in terms of the width (or nx) and height (ny) of the picture. Since these are the only pieces of information in the images that specify the image size (no XDR type stuff in the file like with a field), we're guessing that when the read image module or the image viewer reads this file it tries to make some sense of these numbers. If they are wierd (like negative or large) it tries to flip the Endian of ALL the values in the dataset (including the data that defines the alpha, R, G, B of the image). Is this true? We found this out when we tried to write X apps that read in AVS image files. Some seem to work fine but others died because they were not flipping the Endian. We assumed that all the .x files were the same type. Forgive us! You can see this quite easily by using the 'od' command on a couple of these files (like digital.x and avs.x). Allen V. R. Schiano Advanced Scientific Computing Office of Academic Computing University of California, Irvine Irvine, Ca 92727 schiano@uci.edu
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Path: arc1-ca.pugleaf.net!sparky!uunet!usc!news.service.uci.edu!vega.acs.uci.edu!schiano From: schiano@vega.acs.uci.edu (Allen V. Schiano) Subject: read image Endian questions Nntp-Posting-Host: vega.acs.uci.edu Message-ID: <2B2E7F6D.8114@news.service.uci.edu> Newsgroups: comp.graphics.avs Reply-To: schiano@vega.acs.uci.edu (Allen V. Schiano) Organization: University of California, Irvine Keywords: read image module, Endians Lines: 33 Date: 16 Dec 92 00:59:26 GMT