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Date Posted: 17:31:04 08/10/01 Fri
Author: Michel
Subject: Re: Also problems with graphic dimensions
In reply to: Kai Peters 's message, "Also problems with graphic dimensions" on 13:43:46 08/10/01 Fri


Hi Kai,

You are creating a TDibGraphic, then calling LoadFromFile. The base class TDibGraphic does not "know" any file formats. You need to use a derived class.

Here is a routine that should work:

procedure GetGraphicSize( const FileName : String;
var Width : Integer;
var Height : Integer );
var
Graphic : TDibGraphic;
begin
Width := 0;
Height := 0;
Graphic := NewDibGraphic(FileName);
if Graphic = nil then
Exit; { not a registered graphic format }
try
Graphic.LoadFromFile(FileName);
Width := Graphic.Width;
Height := Graphic.Height;
finally
Graphic.Free;
end;

end;

Note that NewDibGraphic is used instead of TDibGraphic.Create. NewDibGraphic returns a graphic object related to the type of file, ie, jpg, png, ...

Best regards,

Michel
>Michel,
>
>I wanted to write a fairly generic function to obtain
>graphics' dimensions. Why does my approach from below
>always returns '0'?
>
>Thanks,
>Kai
>
>
>
>function ObtainGraphicDimensions(graphicfile: String;
>wantedval: Char): Integer;
>var
> dgr: TDibGraphic;
> ext: String;
>
>begin
> ext := Uppercase( ExtractFileExt( graphicfile));
> Result := 0;
> //
> if FileExists( graphicfile) and ((Pos( ext,
>'.PNG.JPG.JPEG.BMP') > 0)) then
> begin
> try
> dgr := TDibGraphic.Create;
> dgr.LoadFromFile( graphicfile);
> //
> if (ext = '.PNG') then
> Result := iif( Upcase( wantedval) = 'H',
>TPngGraphic( dgr).Height, TPngGraphic( dgr).Width)
> else if ((ext = '.JPG') or (ext = '.JPEG')) then
> Result := iif( Upcase( wantedval) = 'H',
>TJPEGGraphic( dgr).Height, TJPEGGraphic( dgr).Width)
> else // must be BMP
> Result := iif( Upcase( wantedval) = 'H',
>(BitmapGraphic( dgr).Height, TBitmapGraphic(
>dgr).Width);
> finally
> dgr.Free;
> end;
> end;
>end;
>
>function iif(cond: Boolean; tval, fval: Variant):
>Variant;
>begin
> if cond then
> Result := tval
> else
> Result := fval;
>end;

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