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Date Posted: 17:15:20 10/12/05 Wed
Author: Michel
Subject: Re: Problem with gray scale bitmap
In reply to: Roberto Pungartnik 's message, "Problem with gray scale bitmap" on 10:37:39 10/11/05 Tue

Hi Roberto,

Technically, there is no difference between a grayscale 256 and color 256 image. They both use a 256 color palette, but with gray, all the R G and B values are the same.

It depends how an image is manipulated before saving it as JPEG. Check the ImageFormat property of TDibGraphic before saving to see if it is ifColor256 or ifGray256.

Best regards,


>Im trying to make a test software In Borland C++
>Builder 5, that converts a 256 gray level bitmap to
>JPEG, but when I try to convert, i receive the message
>"JPEG must be gray scale or true color", but my image
>is a 256 gray scale.
>In one of my tests i used the DemoC4.exe that i
>generated from the samples.
>If I convert an image from 256 colors to gray scale,
>and try to save as JPEG, it works fine, but if I save
>the same image on gray scale(converted using the
>DemoC4) and try to open(with DemoC4)and save as JPEG,
>i got the same error.
>If i look at ImageScrollBox- Graphic- ImageFormat I
>see that my 256 gray sacale image is opened as 256
>colors, not as gray scale, this is a piece of my
> TImageScrollBox *ImageScrollBox = new
>TImageScrollBox( this );
> ImageScrollBox-> LoadFromFile( "ImgBase.bmp", 1 );
> ImageScrollBox-> SaveToFile( "ImgnJpg.jpg" );
> delete ImageScrollBox;
>Anyone have some ideia about this?
>Thanks in Advance
>Roberto Augusto

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