W3C home > Mailing lists > Public > www-style@w3.org > January 2005

Re: Intrinsic size of jpeg images

From: Brian Sexton <discussion-w3c@ididnotoptin.com>
Date: Thu, 27 Jan 2005 18:42:46 -0800
Message-ID: <002a01c504e3$0ceb9460$651aa143@desktop>
To: "Grant, Melinda" <melinda.grant@hp.com>
Cc: <www-style@w3.org>

> Is this correct?  If those in the know could explain why the resolution
> information associated with jpeg images is ignored, it would be greatly
> appreciated.

It is probably because the graphical user interfaces of host operating systems determine the display resolution in terms of both total horizontal and vertical resolutions and dots--or pixels--per inch, the latter of which is often inaccurate because the same total horizontal and vertical resolutions can be displayed on many different displays of different physical dimensions.  Many operating systems make it easy to adjust the DPI/PPI setting, but few people actually do it.

Have you ever used a JPEG image with a lower resolution than your display and stretched it to fit?  If so, it probably looked terrible, right?  That is one reason to not force raster images to DPI/PPI settings other than the current setting of the host interface.  Another reason is that image sizes could vary considerably in relation to other elements within a Web client, as relatively sized text often does between Mac OS and Windows systems.

Kind regards,

Brian Sexton
Received on Friday, 28 January 2005 02:42:47 UTC

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