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Date Posted: 21:24:43 04/20/03 Sun
Author: Michel
Subject: Re: Identify graphic type
In reply to: glup 's message, "Identify graphic type" on 08:14:09 04/19/03 Sat

Hi Glup,

I am not sure if you are using version 2, but this has been added. The class method is,

class function CanRead( const Stream : TStream ) : Boolean; virtual;

and all current TDibGraphic derived classes implement it.

With the TImageScrollBox, you can now load any Envision support graphic without knowing the image type, with

LoadFromStream( const Stream : TStream;
const ImageNo : LongInt );

Best regards,


>I have to create for an existing picture database with
>more than 500.000 pictures a new frontend. Even the
>database tables contain lots of information regarding
>the images stored in blobs, there is no information of
>the image type.
>I have stored the blob content into files and analysed
>it with Linux fileinfo to identify the file type. With
>this information it was easy to load the image with
>the appropirate envision class. For some multi-page
>images I have encountered errors, but the original
>program reported them too.
>I'm not allowed to modify the database structure, e.g.
>to introduce a new field with the image type I had
>identified using fileinfo once during migration.
>Now the question:
>How can I avoid using fileinfo to identify the image
>type? I'm missing something like
>class function TDibImage.CanLoad( const aStream:
>TStream ): boolean;
>If I try to load the image with all possible envision
>classes until I find one where no error occur, the
>identification takes very long and seams not allways
>to be correct. The identifation with fileinfo is at
>least 5 times faster and in my 200 test cases correct.

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