[fpc-pascal] questions on fpimage
Mattias Gaertner
nc-gaertnma at netcologne.de
Thu Jan 5 11:15:49 CET 2017
On Tue, 03 Jan 2017 02:54:05 +0100
Marc Santhoff <M.Santhoff at web.de> wrote:
> Hi,
>
> firstly a happy new year to you all and keep on rocking!
>
> While reading the fpimage unit code I found some pieces I don't
> understand and could not clear up reading the docs. Here we go:
>
> <code>
> TFPCustomImage = class(TPersistent)
> [...]
> public
> [...]
> property Extra [const key:string] : string read GetExtra write SetExtra;
> property ExtraValue [index:integer] : string read GetExtraValue write SetExtraValue;
> property ExtraKey [index:integer] : string read GetExtraKey write SetExtraKey;
> procedure RemoveExtra (const key:string);
> function ExtraCount : integer;
> </code>
>
> Whats that good for? Ist to tag images inside my own program or does it
> handle image meta data like EXIF and stuff?
Yes. Both.
> And at the end:
>
> <code>
> initialization
> ImageHandlers := TImageHandlersManager.Create;
> </code>
>
> Looking at this class it seems to be sort of a type registry, maybe able
> to detect type and name or instantiate the reader and writer classes.
> How ist that to be used and do I need to care for?
All image formats register themselves there.
It is used by
TFPCustomImage.FindHandlerFromExtension
and
TFPCustomImage.LoadFromStream
You can query it yourself or use the above.
Mattias
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