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Date Posted: 21:14:02 01/05/03 Sun
Author: Michel
Subject: Re: Evaluting Envision 2 ....
In reply to: Roberto Nicchi 's message, "Evaluting Envision 2 ...." on 11:19:58 01/03/03 Fri


Hi Roberto,

Currently, you need to load the images to get the size an dimensions. The JPEG header is easy to read:

TJpegHeader = packed record
SOI : array [1..2] of Byte;
APP0 : array [1..2] of Byte;
Length : array [1..2] of Byte;
Identifier : array [1..5] of Byte;
Version : array [1..2] of Byte;
Units : Byte;
Xdensity : array [1..2] of Byte;
Ydensity : array [1..2] of Byte;
XThumbnail : Byte;
YThumbnail : Byte;
end;

This is what you find at the beginning of the file.

For TIF this is hard because the tags may be at different locations in the file.

For the JPG support in TIF files, it is unfortunate that imaging for Windows does not use the revised specs. TIFF is quite complex and Envision uses the reference library www.libtiff.org. Your best workaround would be to avoid using the JPG compression in TIFF and use Packbits instead, but your file will be larger.

Best regards,

Michel


>I'm now evaluating Envision Ver 2
>
>It looks interesting but i have some questions.
>
>Can someone tell me how i can do the following things:
>
>1) find the pixels per inch (DPI) of a jpj or tif file
>without load all the image.
>
>2) find the dimension in pixels of a jpj or tif file
>without load all the image.
>
>I see also (reading other messages and trying) that
>Envision is using a new compression algoritm that is
>not yet supported from other softwares. I see that tif
>saved from the demo program can't be opened from my
>windows XP Imaging or from windows Paint. I think this
>can be a problem because it can happens that my
>customers send images by email to other users. Are you
>planning to do sometthing with this "problem" ?
>
>that's all for now
>
>thank you
>
>Roberto

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