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Sizes of an image - display v printing

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Sizes of an image - display v printing chuckie 12 Mar 18:44
  Sizes of an image - display v printing Ofnuts 13 Mar 09:27
   Sizes of an image - display v printing chuckie 13 Mar 17:36
2020-03-12 18:44:33 UTC (24 days ago)
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Sizes of an image - display v printing

I am little confused ...

I have an image that is 828 pixels wide.

If I open it in Paint, and HyperSnap or GIMP and view it at 100% and use a ruler, the width of the image is about 23cm.

If I drag the image into a Microsoft Outlook email (embed it) or go to the GIMP Print Size window, they both report it to be 3.5cm wide!

So, the GIMP editor shows it at a nice size of 23cm visually, but to print, or embed it in Microsoft Outlook email it is only 3.5cm width.

Why is it then that the display of it in the editor is 23cm? What changes need to be applied so that the image will embed into Microsoft Outlook email at 23cm? Certainly, I was expectign it to embed at the scale I see it in the GIMP viewer and not the anticipate scale for printing.

chuckie (via www.gimpusers.com/forums)
Ofnuts
2020-03-13 09:27:08 UTC (24 days ago)

Sizes of an image - display v printing

On 12/03/2020 19:44, chuckie wrote:

I am little confused ...

I have an image that is 828 pixels wide.

If I open it in Paint, and HyperSnap or GIMP and view it at 100% and use a ruler, the width of the image is about 23cm.

If I drag the image into a Microsoft Outlook email (embed it) or go to the GIMP Print Size window, they both report it to be 3.5cm wide!

So, the GIMP editor shows it at a nice size of 23cm visually, but to print, or embed it in Microsoft Outlook email it is only 3.5cm width.

Why is it then that the display of it in the editor is 23cm? What changes need to be applied so that the image will embed into Microsoft Outlook email at 23cm? Certainly, I was expectign it to embed at the scale I see it in the GIMP viewer and not the anticipate scale for printing.

When you look at your picture at 100% in Gimp, Paint and other applications, it is displayed "dot for dot", one pixel of the picture is one pixel on your screen, and therefore it is displayed using your screen definition (so given the size you report we can assume that the resolution of your display is 828/(23/2.54)=91 pixels/inch).

On the other hand your picture has an embedded "print definition" which is used for printing, in your case 828/(3.5/2.54)=600 pixels/inch. This sets a theoretical size for the picture, size at which the picture is printed (as long as everything in the print stack abides to it).

Print definition (in Pixels/inch), print size (in inches) and size (in pixels) are related by the formula:

print size = print definition * pixels

Note that this means that you can only pick two of these values, the third is determined by the first two.

In Gimp you can un-tick "View>Dot for dot", in which case the picture will be shown at the print size, if your screen resolution is properly set (see Edit>Preferences>Interface>Display).

When you create the image, you should set the size in pixels big enough so that you can print it at the required size with a print definition of at least 200 pixels/inch (photo) preferably 300 or more if there is text/logos or other computer-generated graphics. The advanced options in "File>New..." let you enter a print size and print definition, and compute the required size in pixels.

2020-03-13 17:36:30 UTC (23 days ago)
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contact
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Sizes of an image - display v printing

When you look at your picture at 100% in Gimp, Paint and other applications, it is displayed "dot for dot", one pixel of the picture is
one pixel on your screen, and therefore it is displayed using your screen definition (so given the size you report we can assume that the resolution of your display is 828/(23/2.54)=91 pixels/inch).

On the other hand your picture has an embedded "print definition" which
is used for printing, in your case 828/(3.5/2.54)=600 pixels/inch. This
sets a theoretical size for the picture, size at which the picture is printed (as long as everything in the print stack abides to it).

Print definition (in Pixels/inch), print size (in inches) and size (in pixels) are related by the formula:

print size = print definition * pixels

Note that this means that you can only pick two of these values, the third is determined by the first two.

In Gimp you can un-tick "View>Dot for dot", in which case the picture will be shown at the print size, if your screen resolution is properly set (see Edit>Preferences>Interface>Display).

When you create the image, you should set the size in pixels big enough
so that you can print it at the required size with a print definition of
at least 200 pixels/inch (photo) preferably 300 or more if there is text/logos or other computer-generated graphics. The advanced options in
"File>New..." let you enter a print size and print definition, and compute the required size in pixels.

Reducing the DPI from 600 to 200 made a big difference for dragging the image into an email. Thank you.

chuckie (via www.gimpusers.com/forums)