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Date Posted: 21:29:10 06/08/00 Thu
Author: Michel
Subject: Re: GrayScale images
In reply to: Bill Mears 's message, "Re: GrayScale images" on 09:27:35 06/08/00 Thu


Hi Bill,

Have you checked to see what is the resulting image format after the scan? I assume it is ifColor256, and this is why the TJpegGraphic does not save it. Unfortunately, the ImageFormat is a read only property, so it cannot be changed directly. I would try using the TImageFormatTransform, to change it to ifGray256 before saving it. This is somewhat confusing, because I suspect that even if you requested ifGray256, the resulting image is ifColor256, since there is really no difference between the two, except the palette.

Best regards,

Michel

> >
> > Hi Joerg,
> >
> > As you have seen, the OnAcquire event returns a
> > DibHandle from the scanner. Then
> > AssignFromDIBHandle(DibHandle) is used to get the
> > resulting image. Unfortunately, from a DibHandle
> > (which is really a memory handle holding bitmap
> > information), it is not possible to determine if an
> > image is gray scale, as a gray scale image is really
> a
> > color palette image with all palette entries having
> > gray colors.
> >
> > JPEG does not support color palette images so this is
> > why you are getting this error. You will need to
> > change the format from ifColor256 to ifGray256
> > yourself (by looking at the Palette property) before
> > saving as JPEG.
> >
> > Best regards,
> >
> > Michel
> >
> > > Hi Michel,
> > >
> > > it's again me... Now I tried to scan and save
> > > grayscale image but failed. Envision function to
> get
> > > image format never returns gray scale (EnScan.pas).
> > > Saving scanned image as JPeg creates exception like
> > > "image must be grayscale or truecolor". Please
> check
> > > it, thank you.
> > >
> > > Best regards from germany
> > > Joerg
> I tried using the "RequestedImageFormat" of ifGray256
> to save as a Jpeg and I got the same error. The only
> way I could get the scan done was to save as a PCX as
> ifBlackWhite

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