Ok.... So "compression" is the best measure of quality? -----Original Message----- From: Andy Matthews [mailto:[EMAIL PROTECTED] Sent: Thursday, January 03, 2008 11:24 AM To: CF-Talk Subject: RE: Manipulate the DPI with cfimage?
Mark... You're also confusing image quality (compression) with DPI (or pixel dimensions). At it's heart, a bitmapped (or raster) image, is simply a series of 1 pixels blocks with specific color assignments. An image doesn't know what quality (compression) it is. It also doesn't know what resolution it is. The only thing an image knows about itself, is how many pixels it is comprised of, and what specific color each of those pixels are. I think Claude's usage of the term "density" is an excellent choice. DPI simply indicates how many pixels are crammed into your unit of measure. If you REALLY want to start bending your head you'd start talking LPI (lines per inch), or linescreen. That's usually a better measure of print quality than is DPI. Bit depth simply refers to the total number of colors available to an image. -----Original Message----- From: Mark Kruger [mailto:[EMAIL PROTECTED] Sent: Thursday, January 03, 2008 11:06 AM To: CF-Talk Subject: RE: Manipulate the DPI with cfimage? Claude, Hmmm.... Ok this is interesting to me. The argument below seems semantic.... So I think I am missing something. I'd like to get my head around this. Visually DPI represents "dots per inch" - it's a measure of "density" in printing. The higher the DPI the better the quality of printing - right? Ok I get that so far.... On a monitor the "pixel" is in one way a measurement of size - as in "how many pixels can I get on the screen". When I look at an image in Fireworks I get a measurement of pixels at the bottom - 800 by 600 for example - 96 "pixels per inch". That's a size measurement. But on a screen or inside the file - what is representative of the "quality" of the file as it is presented on a monitor... In a JPG file there is a "quality" setting for exporting. This setting (as I understand it) is really related to the lossy compression that is used and dictates how aggressively the file is to be compressed. But this is where non-imagy folks like me get confused. I DPI is not the same as "resolution" what is the proper term? Is it "bit depth" or the number of colors used or what. How do you reference the quality of the image on the screen without using the word "resolution"? And if resolution IS the proper term for the "quality" of an image, then doesn't it have at least some correlation to DPI? In my head a JPG is still a group of pixels - a bitmap... (even though I know it is more than that). I envision that the smaller the pixels are and the closer they are packed tightly together - the better the "resolution" of the picture - yes? So in my head, DPI and JPG's pixels have a similar function. I need education on this point. What is the proper way of referring to the "quality" of a digital image? Camera's use "mega-pixels" ... But doesn't that mean smaller pixels packed "closer" together? Isn't it analogous to having 180 pixels per inch instead of just 96 pixels per inch? And doesn't that translate pretty well into the idea of "density"? Help out a struggling graphically challenged coder :) -mark Mark A. Kruger, CFG, MCSE (402) 408-3733 ext 105 www.cfwebtools.com www.coldfusionmuse.com www.necfug.com -----Original Message----- From: Claude Schneegans [mailto:[EMAIL PROTECTED] >>I've argued many times myself (as author of ImageCFC) that "DPI" is not a function of the image itself, but the meta-data of the image, as the DPI is *ONLY* used for print. ....... or scanning, I couldn't agree more. The resolution is a quality of instruments, images have no resolution. ....... and DPI do not even express a "resolution" as currently said, but a "density", anyway... ;-) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~| Adobe® ColdFusion® 8 software 8 is the most important and dramatic release to date Get the Free Trial http://ad.doubleclick.net/clk;160198600;22374440;w Archive: http://www.houseoffusion.com/groups/CF-Talk/message.cfm/messageid:295765 Subscription: http://www.houseoffusion.com/groups/CF-Talk/subscribe.cfm Unsubscribe: http://www.houseoffusion.com/cf_lists/unsubscribe.cfm?user=89.70.4
