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Date Posted: 20:11:39 09/16/03 Tue
Author: Michel
Subject: Re: Create PNG with transparent background
In reply to: glup 's message, "Create PNG with transparent background" on 16:32:03 09/16/03 Tue

Hi Glup,

Here is from the help file:

Transparent images (with palettes and true color) are supported with the TPngGraphic class. In order to create a transparent image, the SaveTransparent property must be set True, and the TransparentColor must be set to a color that exists in the image. The SaveWithBackground and BackgroundColor determine if a default background color will be saved with the transparent image.

So it should be

wPng.SaveTransparent := True;
wPng.TransparentColor := ...
wPng.BackgroundColor := ...

Best regards,


>I try to convert a Bitmap to a PNG with transparency:
>procedure TForm1.SaveAsPngStream( const aBmp: TBitmap
> wPng: TPngGraphic;
> wPng := TPngGraphic.Create;
> try
> wPng.Assign(aBmp);
> wPng.TransparentColor := wPng.RGB[0, 0]; // = (R:
>255; G: 0; B: 255);
> wPng.BackgroundColor := wPng.RGB[0, 0];
> wPng.Transparent := true;
> fImg.Clear;
> wPng.SaveToStream(fImg);
> wPng.SaveToFile('test.png');
> finally
> wPng.Free;
> end;
>If I load test.png with another graphic app I see no
>area transparent, even the complet background does
>have that color.
>Have I missunderstood something?

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