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Date Posted: 21:26:54 10/26/03 Sun
Author: Michel
Subject: Re: Detecting PNG Transparency and Progressive
In reply to: LoST 's message, "Detecting PNG Transparency and Progressive" on 10:23:20 10/25/03 Sat


Hi,

TPngGraphic will display tranparent images with a background, but does not set the property values when loading. TPngGraphic.SingleLoadFromStream needs a few changes. I should have some time to look at this tomorrow.

Best regards,

Michel


>Hi,
>
>I want to write a simple program that decompress PNG
>files, but keep all other properties (transparency and
>progressive_mode). Here is what i wrote :
>
>/******************************************************
>****/
>
>PNGSource := TPNGGraphic.Create;
>PNGSource.LoadFromFile(Fp);
>
>if PNGSource.Transparent then
>PNGSource.SaveTransparent:=True;
>Else PNGSource.SaveTransparent:=False;
>
>PNGSource.SaveProgressive:=False;
>PNGSource.CompressionLevel:=pcLow;
>PNGSource.SaveToFile(Fp);
>PNGSource.Free;
>
>/******************************************************
>****/
>
>Problems are :
>
>1/ PNGSource.Transparency is always False (even with a
>png file that shows transparency in paint shop pro)
>
>2/ I can't know if the original png file was saved
>using progressive mode or not
>
>3/ You can add a pcNone in the TPngCompressionLevel
>that sets zlib compression to None :)
>
>If one of you can help, thanks in advance !
>
>LoST

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Replies:

  • Re: Detecting PNG Transparency and Progressive -- Michel, 21:07:08 10/30/03 Thu
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