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RE: Netscape and IE images

From: Dave J Woolley <DJW@bts.co.uk>
Date: Fri, 4 Feb 2000 11:52:23 -0000
Message-ID: <81E4A2BC03CED111845100104B62AFB53F3FDA@stagecoach.bts.co.uk>
To: www-html@w3.org
> From:	rev-bob@gotc.com [SMTP:rev-bob@gotc.com]
> 
> > and JPG and GIF are coded for screen or RGB (Red, Green, Blue).
> 
> That's accurate, at least as far as I can attest.
> 
	JPEG is normally internally coded as YUV (intensity and two
	colour components, as used in colour TV - the colour components
	are normally recorded with lower resolution than the intensity
	component).

> True animation (multiple frames): GIF and PNG, but not TIFF, BMP, or JPG.
> 
	I wasn't aware that PNG permitted animation.  TIFF allows
	multiple frames per file, even if no browser animates them
	(this is normal case for TIFF fax images, as viewed by Wang/
	Kodak/Eastman Imaging in Windows).

> Lossless data storage: All but JPG.
> 
	The palletisation process in GIF is lossy, although the losses
	don't accumulate if the image is reprocessed.  (With dithering one
	even trades spacial resolution for colour resolution.)

> High color range: All but GIF, which is limited to 256 different colors at
> most.
> Simple transparency (one color): GIF and PNG only.
> Complex transparency (shades): Multi-channel PNG only, map stored in alpha
> channel.
> 
	Also XCF, the native GIMP format.  This also supports animation
	and layered images.

> Smallest image size (complex image): JPG.
> 
	Natural scenes, not complex images.

> Largest image size (any image): TIFF/BMP.
> 
	TIFF files can be JPEG or LZW encoded, so this statement is only
	true of a sub-class of TIFF.  In fact, for black and white text
	scans, TIFF with Group 4 FAX encoding is probably the best format.
Received on Friday, 4 February 2000 06:58:49 GMT

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