Hi! On Fri, 17 Mar 2006 09:46:16 +0100 Barry wrote:
> Simon M. Campden-Main wrote: > > Good morning, folks. > > > > Can any one direct me to a snippet or suggest an approach > > to obtaining the resolution of an image [file] with PHP. > > [ . . . ] > > There is no way you can do it. > To have on screen e.g. 40 ppi or 80 ppi when the image has a > size of 400x400 pixel you would have to read out the image > how big a pixel in it is. at 80 ppi you would have your > normal image and on 40 ppi the pixels used per dot would be > duplicated. you still have 400 pixel in width and you would > not be able to "count" the pixels who got duplicated. > > If you are lucky it's written in the file. Otherwise no > chance. > > The normal screen resolution is: with an average of 0.26 mm ~ > 3.8 pixel/mm ~ 97 pixel per inch. > No matter what kind of "resolution" you would choose > (800x600,1024x768 etc.) Reading the surrounding sentences, I think I can see where you're coming from. But, the above statement is a bit confusing. There is a reason why it's called "pixel per INCH". And it definitely have something to do whether your monitor is set to 800x600, 1024x768, etc. A 15-inch monitor at 800x600 will have around 53ppi x 40ppi (800 pixels divided by 15 inches, etc.) and *the same* monitor at 1024x768 will have around 68ppi x 51ppi. If your 15' monitor is normally setup at 1024x768, everything (images, etc.) will look a bigger if the same image is viewed using the same monitor at 800x600. This happens because the pixels are now "bigger". (One image "pixel" is now compose of many physical dots on the screen.) But, I guess, you already knew that. (^_^) > an image having for example 48ppi would have pixels that use > 2x2 pixels (4 pixels) as one colored pixel and so on. > > Now guess what you see when you have 194 ppi. > Nothing, it's still 97 ppi because it's not possible for the > screen to view anything else. Normally the screen would just > duplicate the imagesize from 400x400 to 800x800. > > Greets Barry > HTH & HAND, - Edwin - -- "He that is slow to anger is abundant in discernment, but one that is impatient is exalting foolishness." - Proverbs 14:29 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
