I see it said pretty much everywhere that you can't upscale a non vector image without some lossiness and blur, but how does the zoom tool work differently?

Example: I'm trying to make this: enter image description here about twice as big.

When using the zoom tool in a program like GIMP or Paint.NET or Picture Viewer, there is very little blurriness even when made much bigger, as shown here: enter image description here

But when I use the scale tool in GIMP on any of Cubic, Linear or Sinc mode, the image becomes blurry, particularly the edges of each "pixel".

I guess using the zoom tool and printscreen>paste into a new window is ONE solution, but is it the only/best one?

  • What you want is called either box filtering ( but only on upscaling does it work like this) or nearest neighbour filtering. But yes the filter you chose would do that. – joojaa May 25 '17 at 5:58
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    Possible duplicate of How can I 'blow up' small pixel art? – Cai May 25 '17 at 6:35

Try to shrink this:

enter image description here

It's easier than making something bigger.

The black outline need some manual work to make it blocky if it's wanted. But test, if this is useful. The white fill should be exact - it's not copied from elswhere, it's from your image, only the anti-aliasing is quessed and taken back. It didn't work perfecly to the outline that had sharp blocky outer edges. I put a new smooth outline.

NOTE: Download this PNG, if you copy and paste it, the result is random. Probably you lose the transparent background.

The receipe:

Your original small r was enlargened to 800% pixel dimensions. There are many good resizing programs that quess the missing details and can take back some obvious anti-aliasing. On1 Perfect Resize was used here. The result:

enter image description here

The outline isn't especially nice, but there was no glue to do it otherwise. The interior was anti-aliased. On1's resizer by default thinks the interior has originally had a sharp edge.

I selected the interior, smoothed the selection (not blurred nor feathered) and painted it full white. Then I took the interior to Inkscape (=Ctrl+C, Ctrl+V)

In Inkscape I traced the interior with default settings. See the following cartoon:

enter image description here

  1. The enlargened r with whitened interior. This was not traced!

  2. The interior after the tracing, turned to black and a thick black stroke was inserted

  3. The interior after the tracing, only white fill, no stroke

  4. this is 3 and 2 piggybacked, the same as already offered to be shrinked

ADDENDUM: On1 Resizer is a high cost program. There's also usable freeware. I have tried Smilla Enlarger. https://sourceforge.net/projects/imageenlarger/

Its results are a little softer than On1's. But they can be sharpened. Smilla seemingly tries to quess also what's behind the blocky outline of your r. Heres a enlargening result which is made in Smilla and then made sharp in GIMP.

NOTE: This is bitmap, no tracing attempted.

enter image description here

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Using Interpolation: None instead of Cubic, Linear, or Sinc gave me the results I was looking for.

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  • 1
    And this is what the Zoom effectively does, too. – Michael Schumacher May 26 '17 at 0:01

You will achieve the best possible result increasing the size of the image so that it becomes 4 times as much. The simple explanation is that doing so, every pixel will be drawn on 4, and there will be no processing or alteration of the image that you can't control. An example of this is seen when projecting an HD image on a 4K screen.

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