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Date Posted: 07:15:15 05/17/00 Wed
Author: Michel
Subject: Re: Acquire with ShowUI=true
In reply to: Jöerg 's message, "Re: Acquire with ShowUI=true" on 09:41:04 05/16/00 Tue


Hi Joerg,

You are correct, this is a little like the chicken and egg problem. The simplest solution, yes, if to first create a TDibGraphic to get the image format. Then you may create a new TDibGraphic derived class from the appropriate format, and assign it from the first DibGraphic.

If you want to create a function which returns the image format without creating an entire TDibGraphic, you could use the code in AssignFromDibHandle,

var
pBmpInfoHeader : ^TBitmapInfoHeader;
pBitmapInfo : Windows.PBitmapInfo;
BitsPerPixel : Word;
ImageFormat : TImageFormat;

begin

pBmpInfoHeader := GlobalLock(InDibHandle);
try
pBitmapInfo := Pointer(pBmpInfoHeader);

BitsPerPixel := pBmpInfoHeader^.biBitCount;

if BitsPerPixel in [16,32] then
ImageFormat := ifTrueColor
else
ImageFormat := GetImageFormat(BitsPerPixel);

finally
GlobalUnLock(InDibHandle);
end;
end;

Best regards,

Michel

> Hi Michel,
>
> sorry, but where do I get the property "ImageFormat"
> without a Graphic class?
>
> case Graphic.ImageFormat of
> ifBlackWhite: {do something}
> end;
>
> Do I need to create a TDibGraphic first, use case
> statement and create a TTiffGraphic (i.e.) second? Or
> can I get ImageFormat from DibHandle?
>
> Thanks and best regards
> Joerg
>
> >
> > Hi Joerg,
> >
> > In your code, the problem is that you are creating
> > your Graphic as a TDibGraphic, so you cannot typecast
> > it to a TTiffGraphic or TJpegGraphic. Instead, create
> > your Graphic object in the case statement itself:
> >
> > case Graphic.ImageFormat of
> > ifBlackWhite:
> > begin
> > Graphic := TTiffGraphic.Create;
> > Graphic.AssignFromDibHandle(DibHandle);
> > Graphic.XDotsPerInch := XDpi;
> > Graphic.YDotsPerInch := YDpi;
> > Graphic.Compression := tcGroup4;
> > Graphic.SaveToFile('c:\temp\test.tif');
> > end;
> > ifTrueColor:
> > begin
> > Graphic := TJpegGraphic.Create;
> > Graphic.AssignFromDibHandle(DibHandle);
> > Graphic.XDotsPerInch := XDpi;
> > Graphic.YDotsPerInch := YDpi;
> > Graphic.SaveToFile('c:\temp\test.jpg');
> > end;
> > end; { case }
> >
> > You should also add a default in your case statement
> > to handle other image formats.
> >
> > Best regards,
> >
> > Michel
> >
> > > Hello Michel,
> > >
> > > how can I get information about ImageFormat and
> > > XYResolution with ShowUI=true? I need it to select
> > the
> > > best image filetype and compression.
> > >
> > > Example:
> > > If user acquires a bw image, my app shall save it
> > > automatically as tif fax g4, if he scans truecolor,
> > my
> > > app shall save it as jpeg. Please have a look at
> the
> > > following source. Can I do so or what goes wrong?
> > >
> > > procedure TXImageFrame.Acquire(const DibHandle:
> > > THandle; const XDpi,
> > > YDpi: Word; const CallBackData: Integer);
> > > var Graphic: TDibGraphic;
> > > begin
> > > Graphic := TDibGraphic.Create;
> > > try
> > > Graphic.AssignFromDibHandle(DibHandle);
> > > Graphic.XDotsPerInch := XDpi;
> > > Graphic.YDotsPerInch := YDpi;
> > > case Graphic.ImageFormat of
> > > ifBlackWhite: with TTiffGraphic(Graphic) do
> > begin
> > > Compression := tcGroup4;
> > > SaveToFile('c:\temp\test.tif');
> > > end;
> > > ifTrueColor:
> > >
> TJpegGraphic(Graphic).SaveToFile('c:\temp\test.jpg');
> > > end;
> > > finally
> > > Graphic.Free;
> > > end;
> > > end;
> > >
> > > Thank you very much and regards from germany
> > > Joerg

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