Re: [Gimp-user] problems with understand how to resize images properly

[Steve Kinney <admin pilobilus net>]

On 11/20/2017 09:05 AM, menglor wrote:
> Good Day!
>
> I am a newbie learner to “” and I am trying to accomplish a series of steps, but
> things just don’t seem to work out for me.
>
> I have 2 problems, well more but I wont go into everything 
>
> -     Basically   I am trying to import a picture of varing sizes, and then resize
> them to fit a specific size.
>
> For example,  I am importing an image  that is 5” x 3”,   and wanting to print
> it on a label,
> So I need to be able to copy it out of GIMP, and past it into a Avery Shipping
> Label template in Word.
>
> I have been a little successful, but I am having issues with the sizes changing.

Hi menglor,

The process you describe will give you images of different sizes if the
originals have different DPI values, because when you scale an image to
be a certain number of inches in size, the GIMP looks at the DPI
resolution of the image first, then scales the image to be X number of
pixels wide/tall based on that DPI and the physical dimensions you specify.

Example:  A 300 DPI image scaled to 1" x 1" will come out 300 pixels
wide.  A 150 DPI image scaled to 1" x 1" will come out 150 pixels wide -
half "size" of the 300 DPI one.

Scaling images by adjusting their size in inches (or centimeters, etc.)
is rarely done.  Useful results require resetting the DPI of images as
necessary, so a set of images of the same size in inches, cm or etc.
will also be the same size in pixels.

Or can multiply the size in inches of the output images you want by the
DPI you want, to get the correct dimensions in pixels for /all/ the
images intended to be the same size when printed.  From that point on,
you can just scale your whole batch of images to the same size in pixels
and ignore the size "in inches."

The DPI setting in an image is only a number recorded in the file
header; changing the DPI of an image changes nothing but that one
number, and as far as I know it does not affect the actual or displayed
/ printed size of the image, except when scaling the image in an editor
like the GIMP.

Typical DPI values:

300 DPI for high quality print
150 DPI for office documents etc. where "good enough is good enough"
96 DPI for on-screen display
72 DPI - a legacy default setting based on printers' "point" size

Note that doubling the DPI of an image while maintaining the same print
size when scaling, multiplies the size of the resulting file on disk by
about 4x.  Exporting images in lossless PNG format (vs. lossy JPG) for
maximum print quality also creates much larger file sizes on disk.  So
big, high quality print jobs can take up a lot of space in storage or
time in transit across the network.

You also mentioned printing via a Word document, and that the sizes you
get are a little off.  I think that's to be expected, because word
processors were not intended for "pre-press" work, a.k.a. printing
images with high accuracy.

I use Scribus, a Free desktop publishing application, for pre-press
work.  Make your images, put them on the page exactly where you want
them, export the file as PDF and print that:  Viola, accurate results.

For really precise positioning on page, i.e. when printing on peel and
stick label stock or etc., it may be necessary to print a test page,
measure any placement errors, and adjust the Scribus master document to
get your required results from that particular printer.

https://www.scribus.net/

:o)



> Steps I am completing.
>
> 1-    Open Image.
> 2-    Click menu “Image”  and then click Scale image
> 3-    I assign the Size height as  1.30 inches  (because of the linked reference,
> width defaults to  2.0 inches ISH
> 4-    Resolution seems to imply its  76 x 76
> 5-    And it seems like it works, though when I COPY and paste into Word and print.
> The size is a little off.
>
> However, I went on to the next picture, which ultimately was a desktop  image , 
> I completed the following
>
> 1-    Open Image.
> 2-    Click menu “Image”  and then click Scale image
> 3-    I assign the Size height as  1.30 inches  (because of the linked reference,
> width defaults to  2.0 inches ISH
> 4-    Resolution seems to imply its  560 x 560  (don’t have the real numbers handy)
> 5-    Then I copy it , and then Paste into Word.
> 6-    When I look at the image in my template  the image height should be 1.3, but
> its about 2.3.  and the width is also messed up.
>
> I am confused. If I tell them image to be 1.3  why is it not listening?   I
> understand there is a setting called Print size somewhere, but I am trying to
> make the image  Size X, but something else is getting in the way.
>
>
> I am hoping someone can give me an answer,  or maybe point me to a Youtube video
> that goes over it.   I have watched about 6-8 tutorials, but I cant find
> anything that  goes into that whole aspect of