i need this for a job , my company is ask it , i just found this
http://blenderartists.org/forum/showthread.php?t=54035
and i just dont know how to proceed , also its from 2002 , is there any news on this ?
'ossamattah?
Don’t know how to use a calculator?
Sorry, sorry…
…but seriously, do you really “need” this? It’s a very simple calculation to perform.
Did you try the python script from that thread?
“DPI” means “dots per inch,” which really means pixels per inch when talking of digital images, and is a measure of the resolution of an image when reproduced in some real-world medium, like offset printing or high-res inkjet. It has little correspondence to any parameter within Blender, since Blender doesn’t output to any real-world device except a monitor, which has a pixel rez of 72-96 dpi depending on the model (this is true of all real-world devices, btw – their “dpi” can vary from one to the next).
So, to determine a “dpi” for an image made in Blender, you first have to determine how large the image will be reproduced in the real world, let’s say ink on paper.
Say your image is to reproduce at 10" x 10" and the image size in pixels is 1000x1000. Thus you have 1000 pixels covering a 10" linear measure, and that means 1" has 100 pixels, so your “dpi” for this reproduced image is 100 pixels per inch, usually abbreviated to 100 dpi.
Here’s the basic math: pixel dimension/linear image dimension (in inches) = dpi . Make sure you use the same “side” for doing this formula. i.e., width in pixels and width on paper
So, now you have a way of determining dpi for any image usage, as long as you know the image’s pixel dimensions (which is what Blender uses) and the size of the reproduced image that will be made from it. Example: if your 1000x1000 image reproduces at only 4" x 4", then the dpi = 1000/4 = 250 dpi.
You can also use this formula to determine the appropriate pixel dimensions for a rendering, i.e., if you have a 5" x 4" printed picture space and need a 300 dpi rez, then your image must be at least 1500x1200 pixels in size to meet the requirements.
… or if you don’t want to do the calculations yourself (or use the Basse’s script from the cited thread) you can always just open up photoshop or gimp (or whatever 2d app you use) create a new image with the real world dimensions and DPI you require. This image will have your desired pixel dimensions.
I use this method frequently. Most of what I create these days is for video projection or still images made into 35mm slides, so DPI (PPI) doesn’t matter, only image size and proportion. But occasionally I need to make related images for print in the local newspaper, and they want everything in JPG format at 300 DPI.
GIMP to the rescue! I open the image in GIMP, then Image>Print Size and change the dpi accordingly. Then I save the image as a JPG and I’m done with it.
Using apps like P-shop & Gimp as dpi calculators is a bit of overkill imo, plus, when you’re in a client meeting, and they ask you a question related to dpi and the image you’re producing for them (like whether you can enlarge the image by 62.5% and not have it be under-rez for the print job), having to haul out your laptop (if you have one) and launch an image editor to answer the question, when a simple multiplication/division problem (hand calculator or – OMG! – pencil & paper) is all that’s needed, would make one look rather dumb, eh?
Using computers in this way is a crutch rather than a convenience, better to learn the underlying principle (it’s not like it’s rocket science, fgs) so you can use it in any situation and in many different ways.
A pencil? That’s crazy talk! Take an abacus to the meeting! They’ll think you’re an eccentric genius!
snigger
I tend to prepare material in advance when i go to meetings…
“so how much will this all cost me then?” Me: “oh wait, let me get the Bat-Pencil”…
Having said that, the DPI calculation really isn’t rocket science. I’d like to see a client bring THAT up in a meeting…