Sent: 2010-05-12 18:46:35 UTC (almost 2 years ago)

From: uluru75

Set exact print size

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I have a problem with setting print size of images.
When i set it to 148mm and 105mm, it's being set, then i save and close the
image.
However, when i re-open the jpg, it often show the sizes like 148.22mm or
105.05. Basically i don't want anything after the dot, i want exact size.
Does anyone has any idea how to fix it?

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Sent: 2010-05-12 19:14:15 UTC (almost 2 years ago)

From: Branko Vukelic

Set exact print size

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It's probably a series of rounding errors when converting mm to inches
and then inches to pixels. The image should have:

148mm / 25.4mmpi = 5.82677165"
5.82677165" * 300ppi = 1748.0314950000002 px

105mm / 25.4mmpi = 4.133858267716536"
4.133858267716536" * 300ppi = 1240.1574803149608 px

as you can see, not clean round number. You should have something like
1748px x 1240px which translates to roughly 148x104.99mm.

On Wed, May 12, 2010 at 6:46 PM, uluru75 wrote:
> I have a problem with setting print size of images.
> When i set it to 148mm and 105mm, it's being set, then i save and close the
> image.
> However, when i re-open the jpg, it often show the sizes like 148.22mm or
> 105.05. Basically i don't want anything after the dot, i want exact size.
> Does anyone has any idea how to fix it?
>
> --
> uluru75 (via www.gimpusers.com)
> _______________________________________________
> Gimp-user mailing list
> Gimp-user@lists.XCF.Berkeley.EDU
> https://lists.XCF.Berkeley.EDU/mailman/listinfo/gimp-user
>

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studio@brankovukelic.com

Check out my blog: http://www.brankovukelic.com/
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Sent: 2010-05-12 22:18:00 UTC (almost 2 years ago)

From: Burnie West

Set exact print size

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On 05/12/2010 09:46 AM, uluru75 wrote:
> I have a problem with setting print size of images.
> When i set it to 148mm and 105mm, it's being set, then i save and close the
> image.
> However, when i re-open the jpg, it often show the sizes like 148.22mm or
> 105.05. Basically i don't want anything after the dot, i want exact size.
> Does anyone has any idea how to fix it?
>
Images are always saved in integer numbers of pixels.

To get exactly 148mm by 105 mm, a mm should be an exact number of pixels.

The number of pixels you mention is not exactly commensurate with a 148
x 105 mm image,
so the image (if it's really 148.22 x 105.05) will have to be scaled to
be a little bit shorter.

So in the Image->Scale Image tool, select image size in mm, but don't
scale it yet.

Then set the X-Y resolution to exactly number of pixels you want in a mm
(10, say). This makes the specified print size come out exactly in pixels.

Then, click on the chain link on the Image Size x-y pair, so the image
can be scaled to exactly the dimensions you want. Notice that 72 pixels
per inch is 2.8346567 pixels/mm.

Now, enter 148 in the Width textbox and 105 in the Height textbox (the
pixels/mm entry should not change). NOW, scale the image. On this user
list, people have mentioned a few times that the best scaling quality
seems to be Sinc (Lanczos3) interpolation, but YMMV.

Actually, when I did this with a 3872x2592 pixel image, then saved and
reopened the image, it reopened with the image size default set to
inches, and then when I converted that image size to mm, it said 148.01
x 105.01. Then, when I clicked in the pixels/mm box, then the height
box, the .01's went away by themselves. This suggests it was a rounding
error, rather than a size problem.

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