DPI question.

O.k., time for another one of those what-the-hell-is-he-talking-about questions. What's the deal with setting DPI in the FF stand-alone ? I cannot seem to find a place to do that, and I can't imagine that we're supposed to just do the pixel math, then convert it to 300DPI or whatever by changing the stats in another program ? Certainly I am just up too late and missing something easy, so help me out here people. Thanks.

jffe

basically, dpi (dots per inch) and ppi (pixels per inch) are the same thing when you're dealing with digital. dpi is the older, analog rating, where ppi is the newer version in digital. and, it's now more common to say ppi when dealing with digital images.

think of ppi as a multiplier. the easiest way to see this is to create a new image in your graphics program. make a 300 x 300 image at 100 ppi. then make another new image at 300 x 300 with a 200 ppi resolution. you shld notice that when both are open to 100% image size, they are exactly the same size on your screen. seems weird, right? but if you look at the info tab/menu item on each one, you'll notice the one at 100 ppi also says the image is 3 inches by 3 inches, where the one at 200 ppi is rated at 1.5 inches by 1.5 inches or exactly half the inch size of the 100 ppi. so, if you printed both, like dilla says, the one at 100 ppi is going to print a 3 inch by 3 inch image and the other a 1.5 inch by 1.5 inch.

FF doesnt care about this. if you're working with a texture filter, there's no reason to do anything with this. your finished texture image can just be taken and used in another graphic image and stretched to fit or shrunken to fit. and if it's an image filter, the imported image will determine all the necessary sizing. so, FF doesnt need to deal with ppi internally except to read the imported image's size and simply make itself that size for working.

that make sense? and trust me, you're not the only one that gets confused by this and not just in FF.

Filter Forge itself is capable of recognizing image DPI and selected host units when it is running in plugin mode. With some code tweaks it can recognize standalone loaded images DPI also (a lot of image formats do not support resolution, or just don't have this field properly set, so we'll have to resort to some kind of "default" resolution like the current monitor's one).
The problem is that the only place where DPI would be really useful is the Size slider, with the ability to display size not only in pixels, but in resolution-dependent units. We were going to implement the "current units" sizing when you run under Photoshop for example, so if you set ruler units to cm, you'll get "Size, cm" slider with appropriate values, taking into account the image resolution in Photoshop. But then, we thought that this is an almost completely useless feature after all, which will cause confusion ("Why this !@#$%^& Size is in inches?! Give me back my pixels!" (yes, we explored the idea of having a dropdown to choose Size units)), and will have very questionable benefits at the expense of increasing complexity.

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onyXMaster wrote: ("Why this !@#$%^& Size is in inches?! Give me back my pixels!" (yes, we explored the idea of having a dropdown to choose Size units)), and will have very questionable benefits at the expense of increasing complexity.

----Well, I get it now, but it is odd at first because there are several ways to "measure" graphics. I just look at it now like DPI is a formatting term, almost like .jpg or .tif, as in: "what DPI do you need those 5 X 7's in ?", and then I go do the math on the pixels, and set the DPI before saving it, to make it format to the DPI someone wants.
----What about from the FF stand alone though, it always seems to output at 72DPI, is there a way to change that ?

jffe

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onyXMaster wrote: Hint: 72 is the default Windows image DPI (so one pixel equals one typographic point) Filter Forge does not write DPI information in files it saves. It's your graphics software that defaults to 72 DPI when it loads file that does not have DPI information embedded. FYI: General support for DPI fields is built into FF, but since it does not preserve DPI information obtained from files (for reasons specified above), it should not write it, since DPI value itself does not affect the output image file.

----Oh, so I should blame Windows at least partially for reading everything at 72DPI as a default, o.k.
----Is there any reason that FF couldn't be made to tag output with DPI info though as an advanced option ? Seems like that wouldn't be much of a coding chore compared to some things ya'll get asked for eh.

jffe

Well, I meant just the stand-alone version of FF, guess I forgot to note that eh.

jffe

Well, that it defaults to 72Dpi, or more accurately defaults to having no Dpi tag seems alright I guess. But it should maintain any Dpi tagging, and allow for you to tag output for sure, that just seems well, obvious for professional use at any level. Just a simple menu option in the save dialog, and for people who don't know/care, well they can just ignore it and carry on ya know. No offense, but the idea that you could run a graphic tagged with Dpi info through FF, and somehow lose that coming out, is just not at all professional. So yes, Vlad, please idiot proof the Dpi situation, for the sake of myself, and many other idiots using FF ha-ha.

jffe

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Vladimir Golovin wrote: Personally, when I need to change the DPI while preserving the pixel dimensions, I use Photoshop's Image Size dialog with the Resample checkbox turned off.

Oh you're a life saver Val. Thank you!!!

How do I change the default output of 72dpi, to 300dpi from Filter Forge? My clients want 300dpi, and presently, I need to change every output image from the standalone FF to 300dpi, it's a real drag when doing many images. Would prefer to do this from FF, rather than going into Photoshop, etc.