Re: How does one obtain the resolution of an image in PHP?

Hi! On Thu, 16 Mar 2006 14:31:38 -0500 John Hinton <webmaster@ew3d.com> wrote: > Simon M. Campden-Main wrote: > > > > Well, there's the meat of it, isn't it? I wonder how Paint > > Shop Pro comes up with PPI (Image - Image information). > > I have several thousand scanned images with resolution > > ranging from 72 PPI up to 1200 PPI (As reported by Paint > > Shop Pro) and want to discard, or more likely tag as > > rejected, any that suffer a resolution of less than 150 > > PPI. As you might imagine, I find the thought of > > doing it manually with Paint Shop Pro repugnant. Okay, if it was scanned at 72ppi then you can't really print it out again even with a near-similar quality. However, having an image with a 72ppi does NOT necessarily mean that you have an image unsuitable for printing. > PPI or pixels per inch is a printing term. Last time I checked, "dpi" is the printing term. (^_^) dpi (dots per inch) -> printer ppi (pixels per inch) -> monitor/screen > It has nothing to do with viewing on a monitor as a > monitor's pixel setting is your set resolution, as in > 800x600, 1024x768, 1600x1200.. etc. This is a > constantly debated urban legend. A pixel on a monitor > is a pixel... True. > Pixels per inch are used in the printing world and relates to > how many pixels are used to provide one inch of printed > space. Obviously, at least up to the limits of the printer > being used, a high PPI setting produces a higher quality > 'printed' image. This really depends on how big the image is to be printed. Besides, an image/photo taken using a digital camera (at least mine) always defaults to 72ppi. BUT that does not mean that it will come out badly printed at 300 dpi -- it all depends on how big is the size (setting) of the picture when I first took it. > If you don't believe me, use your paint program, change the > PPI of an image and notice how the image doesn't change size > on the screen. Also, do this and switch the image size > display back and forth between inches and pixels.. the pixel > count doesn't change, only the inches change.. but again... > that's the printing world and has nothing to do with display > on a monitor or webbrowser. True. This is basically because most monitors/screens are actually at or near 72 ppi. "screen" !== "printer" (^_-) > So, an image 10,000pixels by 10,000pixels will be huge on > screen. If set to a resolution of 1000ppi, the image would be > printed at 10" x 10", but you still can't view the whole > image on a monitor without zooming out. If resolution we set > to 10,000dpi, the image would print as 1" x 1", but you still > wouldn't be able to view it on a monitor (unless you have an I think you meant, "... but you still would be able ... " > awesome multi-display setup that can reach 10,000 pixels wide > and tall). That's the bottom line. > > So, I keep seeing 'display size' when I'm thinking the term > should be 'printed size'. > > John Hinton HTH & HAND, - Edwin - -- "A capable wife is a crown to her owner." - Proverbs 12:4