How to get image to display at correct size

Post questions on how to use or achieve an effect in Inkscape.
sarahedgecumbe
Posts: 9
Joined: Sat Feb 02, 2019 5:09 pm

How to get image to display at correct size

Postby sarahedgecumbe » Fri Mar 08, 2019 2:17 pm

Hi folks,

So i'm creating an image to print onto fabric.

I changed the setting to 300 DPI (it HAS to be 300 DPI) in the main menu. So i was drawing at 300DPI.

I need to know how big to make the drawing in inkscape to make it print at 21cm x 31cm. at 300 DPI.


as if i make the image 21cm by 31cm in inkscape it prints out way way too big.

what is the maths for this.

many thanks.

User avatar
druban
Posts: 1719
Joined: Fri Nov 20, 2009 10:48 pm

Re: How to get image to display at correct size

Postby druban » Fri Mar 08, 2019 4:26 pm

21 cm/(2.54 cm/in) = 8.27 in x (300 D/in) = 2480 px
31 cm/(2.54 cm/in) = 12.2 in x (300 D/in) = 3661 px

your object/drawing/page needs to be 2480 x 3660 px (rounded down). Don't use cm or in etc, use px for maximum precision
Your mind is what you think it is.

sarahedgecumbe
Posts: 9
Joined: Sat Feb 02, 2019 5:09 pm

Re: How to get image to display at correct size

Postby sarahedgecumbe » Fri Mar 08, 2019 6:01 pm

Champion Druban!!

been trying to reply for two hours but been stuck with a 1 week old baby... :-)

thanks I was wondering if this is the case as i measured the actual print out and measured what i thought it should be and it seems that the actual print out image is 66% ish smaller than what i though through the toyles tile tester . so your numbers are 33 ish % bigger.

what an annoying thing it is not being able to "see" this in inkscape.

I can fix the panel to your numbers now. Many many thanks.

My problem then is figuring out how to "see" this. when i import into toyles tile tester or into gimp it shows the slightly bigger image?

Do i just have to view the image at about 66% size to get a rough idea (and work out the px to get an exact measurement)

thanks so much

Sarah

User avatar
druban
Posts: 1719
Joined: Fri Nov 20, 2009 10:48 pm

Re: How to get image to display at correct size

Postby druban » Sat Mar 09, 2019 11:25 am

Do you mean on screen size? That is so tricky these days because no monitor resolution is standard.

You can go into Inkscape preferences/interface and hold a ruler to the screen and adjust the correction factor so it gets close, and this should be good enough to work in. If you have never done this before it will help considerably.

complicated because dpi and ppi are not the same thing when you switch devices, and therefore it's best if you can avoid as many of the conversions from inches/centimeters to device units as possible. The last conversion (printer) is of course unavoidable....
Your mind is what you think it is.

User avatar
brynn
Posts: 10205
Joined: Wed Sep 26, 2007 4:34 pm
Location: western USA
Contact:

Re: How to get image to display at correct size

Postby brynn » Sat Mar 09, 2019 12:14 pm

I need to know how big to make the drawing in inkscape to make it print at 21cm x 31cm. at 300 DPI.

as if i make the image 21cm by 31cm in inkscape it prints out way way too big.


Whatever size you set in Inkscape, that IS the size of the image. If you exported a PNG at 300 dpi, it's expected that it will be much bigger. But when you print it, you set the size you want, and then you have the right size and the right resolution (300 dpi). Can you find some way to set the size when you print it?

But I'm confused in your last message. Why do you need to see it on the screen at exactly the right size?

You could export a PNG at the correct size (with 96 dpi), and look at that in an image viewer, to see the exact size. But still, as druban indicated, your screen resolution affects that, and it might not be exactly the same size.

I think I know a website that tells how to figure out the exact size. Let's see if I can find it.... Ok, about the middle of this page, it tells you how to figure out the DPI of your screen: http://auctionrepair.com/pixels.html Maybe some info on that page can help you? Edit - And this site might help too? http://www.pxcalc.com/

I think GIMP uses the same resolution as Inkscape, so that doesn't explain why it looks like a different size when you open in GIMP. Unless I'm mistaken about that? You have the zoom factor at 100%, right?

sarahedgecumbe
Posts: 9
Joined: Sat Feb 02, 2019 5:09 pm

Re: How to get image to display at correct size

Postby sarahedgecumbe » Sat Mar 09, 2019 2:37 pm

Many thanks for your replies.... i am going to reply later this evening. I'm stuck with a cranky baby :-)

I need to "visualise" the size and hold up pattern pieces to the screen to look at pattern placement of the images on the fabric.

Will reply shortly with some extra info


many many thanks for your replies.

much appreciated

sarahedgecumbe
Posts: 9
Joined: Sat Feb 02, 2019 5:09 pm

Re: How to get image to display at correct size

Postby sarahedgecumbe » Sat Mar 09, 2019 6:34 pm

Ok so... Just trying to clarify my question. Thanks so much for your help it is very much appreciated.


I have my image in inkscape that is measuring 220px x 220 px (via the top viewer bar) or approx 5.6cm square. give or take.

On exporting to PNG in the PNG export frame it says that the image is 688px at 300 DPI.

The problem is I sent this design to the fabric printer and it printed out at like 13cmx13cm ish (its a repeating pattern on fabric so hard to measure exactly)

I viewed it in toyles tile tester and it was about 19cm2. and in Gimp it was about 19cm2. I originally was expecting it to be about this size.

How do i work out what size the image will actually print out at? I tried printing the image at home on my home printer set at 300DPI and it came out about 19cm as well.


What size would you expect this design to print at?
Do i need to ask the printer specific details? (easier said than done as i give the file to someone else who gets it printed at their printer)


Any advice appreciated.


Sarah

User avatar
brynn
Posts: 10205
Joined: Wed Sep 26, 2007 4:34 pm
Location: western USA
Contact:

Re: How to get image to display at correct size

Postby brynn » Sat Mar 09, 2019 9:36 pm

A cranky week-old infant -- omg -- poor babies (you and baby)!

Regarding holding the pattern pieces up to the screen....well, if there's no other way, I guess, but it would take some more complicated math than I would want to do, to make the image display at its exact size on the screen. Instead, I would consider putting the pattern pieces in Inkscape. Are they very complicated? Or could you draw the pattern pieces? Then you could move them around any way you want, in Inkscape. As long as you draw them at the right size, and the image is the right size, then what you see in Inkscape is all the correct proportions.

Someone else will have to answer some of your other questions, because I get very confused about dpi and resolution. But this is my understanding about how to print at a certain size and resolution.

Set the image size that you want in Inkscape, and it should print exactly that size. Don't let yourself get confused about how other programs handle the image, unless you're going to use those programs. There are other variables that muddy the water, so unless you need to use them, they might just confuse you more.

If you change the DPI (in Inkscape), and you don't set the size when you print it (using your printing software), it will print bigger. That's ok, that's what we expect.

In order to get the higher DPI and the size you want, you have to change the DPI in Inkscape, when you export it. And when you print it, set the size you want using the printer software. Then the image comes out at the right size, with the right dpi.

You'll need to tell the printer what size you want it to print at. You'll need to ask them what kind of file formats they will accept. Although since you're concerned with dpi and resolution, that must mean that you're sending them a raster format. So that probably won't be hard to do.

(This is probably irrelevant, but I wonder why they won't accept vector formats? Using a vector format would eliminate the need for resolution. I guess it must be related to their hard and software?)

As far as I understand, Inkscape apparently handles dpi a little differently than raster graphics software (such as gimp). I suppose, if there's some reason why a fabric printer can't set the size using the printing software, you could use gimp to set the resolution. I couldn't tell you how to do it though.

sarahedgecumbe
Posts: 9
Joined: Sat Feb 02, 2019 5:09 pm

Re: How to get image to display at correct size

Postby sarahedgecumbe » Sun Mar 10, 2019 8:17 am

Thanks Brynn,

She is really very good... just got bad wind... poor bubba.... lucky us.. lol.


The problem is it is NOt printing at the size that it is set in Inkscape. I can't figure out how to resolve that. The printer just takes the PNG image that i create and prints it. (They ask for a PNG image. I could also apparently use a JPG image.)

I guess the problem is i CAN"T set the size at the printer... so i need to know that conversion factor that you were talking about. you suggested that If the DPI is changed in Inkscape then you said you would expect it to print bigger. Its How much bigger i need to know.

Inkscape is telling me the picture is like 5cm but its printing at closer to 12...

I'll see if i can ask the printer person this question. And see why the size is changing between my file and their printer.

It MUST be an easy fix somewhere. Something this difficult to resolve must actually be something totally dead simple.

I'll message the girl again today who can message the printer. This is just so jolly annoying!!

thanks again for your help dealing with my frustrations.

Sarah

tylerdurden
Posts: 2240
Joined: Sun Apr 14, 2013 12:04 pm
Location: Michigan, USA

Re: How to get image to display at correct size

Postby tylerdurden » Sun Mar 10, 2019 10:07 am

As Druban points out, there is pixel size, print size and and screen size.

In Inkscape, I work in the units used at the destination: px for displays, inches for printing (I'm USA), metric for engineering.

The PNG export dialog in Inkscape allows setting the DPI. Printers frequently allow setting the DPI. Ensure they match.

To scale the display, I just make a rectangle 6in wide (in Inkscape controls bar) and zoom in/out in Inkscape until a ruler held up to the screen matches. make note of the zoom setting in the status bar. On my 1920x1080 laptop screen, the zoom factor is 133%.

Image

When I hold a ruler up to the magenta rectangle, it measures 6" on my laptop. On my 55" HD monitor, it would be a good bit larger unless I zoom back.
Have a nice day.

I'm using Inkscape 0.92.2 (5c3e80d, 2017-08-06), 64 bit win8.1

The Inkscape manual has lots of helpful info! http://tavmjong.free.fr/INKSCAPE/MANUAL/html/

User avatar
druban
Posts: 1719
Joined: Fri Nov 20, 2009 10:48 pm

Re: How to get image to display at correct size

Postby druban » Sun Mar 10, 2019 5:03 pm

not sure if I am explaining it properly. e.g. the printer requires 300dpi. Work backwards from this. You want a 10" print? That's 3000 px. Use this to make your object, and set the document to use px. When you export to PNG, if your export dialog is set to 300DPI your print from the printer should be 10 in.
Still a problem? Open the PNG in a raster program, make sure the pixel dimensions are still the same as you calculated (i.e. 3000 px), and resave it with a resolution of 300 DPI.
If you work in other units, the pixel dimensions and therefore the end result will not be as straightforward!
Your mind is what you think it is.

sarahedgecumbe
Posts: 9
Joined: Sat Feb 02, 2019 5:09 pm

Re: How to get image to display at correct size

Postby sarahedgecumbe » Mon Mar 11, 2019 3:54 pm

right,

thanks SO VERY VERY Much for all your wonderful help.

I am however furious at the printer.... right so.... here is the outcome. You are all correct it should "print" at the size it says on screen...

despite the printer knowing (apparently) that i was testing the sizes of the designs and the designs were SIZED panels for use in sewing.... (like they have to be accurate..) he NEGLECTED to tell me that he printed the samples at any old size onto the fabric just to fill out spots and played with the sizing. so each fabric was a different size.

Finally we figured out (language barrier) and many many photos showing the incorrect size. He owned up to doing that.

i mean seriously who prints a sample fabric panel at the WRONG SIZE and doesn't tell you. even after you ask why its not looking right!!!

anyway so now i have a whole heap of fabric panels that are the wrong size as i increased the file size based on how much bigger they needed to be based on the samples. So they will all be wrong... sigh... so much drama... but the outcome is i think i have this solved.

thanks for helping me understand the other aspects of my question. you have all been very helpful and patient.

kind regards
sarah


Return to “Help with using Inkscape”

Who is online

Users browsing this forum: No registered users and 5 guests