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[REBOL] Re: Display device DPI

From: doncox:enterprise at: 22-Oct-2002 10:33

On 21-Oct-02, [atruter--hih--com--au] wrote:
> 1) Are these DPIs (120 and 96) representative of all CRT/LCD display > devices respectively?
Traditionally, CRTs had 72 dpi, but this seems to have crept up in recent years. 72 dpi gives you pixels matching points, which is good for DTP. In practice, now, two users with the same OS and the same CRT monitor will set the screen to different resolutions, and so have different dpi on screen. A printer will have much higher dpi than any display.
> 2) Does the OS know this number (the display DPI) and how can I access > it?
Only if it knows the size in inches of the user's monitor, which isn't likely if you think about it.
> 3) Have others hit this, or a similar, WYSIWYG / scaling issue?
It happens all the time in Photoshop.
> 4) Do other file formats (eg. PDF, Word, Open Office, etc) have similar > issues (where the image dimensions are given in a unit of measure > other than pixels, and a document is generated on one display device > and viewed on another)?
If you are preparing an image for a web page, you have absolutely no idea how big it will be on the client screen in inches/mm. If you are preparing an image for print, you have to decide the dpi you need for print quality, and the size on paper, and work back to the resolution needed in pixels to get that result. Some image files have dpi information in the header and others don't.
> 5) Am I just approaching this from the wrong POV?
Possibly. Regards -- Don Cox [doncox--enterprise--net]