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Date Posted: 17:55:52 06/15/01 Fri
Author: Michel
Subject: Re: How can TImageFormatTransform apply to TBitmap?
In reply to: wto 's message, "How can TImageFormatTransform apply to TBitmap?" on 11:30:24 06/15/01 Fri


Unfortunately, the transform classes only work with classes derived from TDibGraphic, as the transform classes require the RGB property in TDibGraphic.

The palette of Bitmap and BitmapGraphic will have changed with reducing the color to 256. I assume you original is in true color.

The last line,

Bitmap.Assign(BitmapGraphic) will not give you the desired results. Assign a TBitmapGraphic to a TBitmap will convert the Bitmap back to 24 bit. Ideally it would be better to work with TBitmapGraphic from the start. If this is not possible a better solution to,


would be to use a memory stream.

Stream := TMemoryStream.Create;
Stream.Seek(0, soFromBeginning);

Best regards,


>I want to apply TImageFormatTransform to a TBitmap?
>How should I do? Currently I use a urgely method:
>procedure MyTransform(Bitmap: TBitmap);
> BitmapGraphic: TBitmapGraphic;
> ImageFormatTransform: TImageFormatTransform;
> BitmapGraphic := TBitmapGraphic.Create;
> BitmapGraphic.Assign(Bitmap);
> ImageFormatTransform := TImageFormatTransform.Create;
> try
> ImageFormatTransform.ImageFormat := ifColor256;
> ImageFormatTransform.Apply(BitmapGraphic);
> Bitmap.Assign(BitmapGraphic);
> finally
> ImageFOrmatTransform.Free;
> end;
>And I want to know that after the transformation, has
>the Palette of Bitmap and BitmapGraphic been changed?

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