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Date Posted: 21:17:21 12/11/03 Thu
Author: Michel
Subject: Re: How to detect non bmp files and convert automatically to bmp grayscale in code
In reply to: Andrew Diabo 's message, "Re: How to detect non bmp files and convert automatically to bmp grayscale in code" on 03:31:14 12/09/03 Tue

Hi Andrew,

GuessDibGraphicClass returns a class type, not an object instance. The typecast,


is not valid because DibClass is not an object instance. You can create the object by doing,

DibGraphic := DibClass.Create;
if DibGraphic is TBitmapGraphic then

For your purpose, you can use the TDibGraphic.CanRead class method,


if TBitmapGraphic.CanRead(Stream) then
... stream is a bmp stream

Best regards,


>Hi Michel,
>Thanks for taking the time to respond. I'm having a
>little difficulty understanding the concept, but
>following is my attempt to do the GuessDibGraphicClass
>with no success. Can you please tell me where I went
>procedure TForm1.LoadFile( const FileName : String );
> Stream: TFileStream;
> DibClass: TDibGraphicClass;
> Stream := TFileStream.Create(FileName, fmCreate);
> try
> Stream.Seek(0, soFromBeginning);
> DibClass := GuessDibGraphicClass(Stream);
> if TDibGraphic(DibClass) is TBitmapGraphic then
> Edit1.Text := 'Bitmap'
> else
> Edit1.Text := 'Not a Bitmap';
> finally
> Stream.Free;
> end;
>>Hi Andrew,
>>You can use the function EnDiGrph.GuessDibGraphicClass
>>to determine the file format from the contents of the
>>file. If TBitmapGraphic is not returned, then it is
>>not a bitmap. You can then load the file in the
>>appropriate TDibGraphic derived class, and assign it
>>to a TBitmapGraphic to convert it. Then you can use
>>the TImageFormatTransform to convert it to grayscale.
>>Best regards,

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