<p>From the <a href="http://docs.gimp.org/en/plug-in-gauss.html" rel="noreferrer">GIMP docs</a>:</p>
<blockquote>
<h3>IIR</h3>
<p>IIR stands for “infinite impulse response”. This blur works best for large radius values and for images which are not computer generated.</p>
<h3>RLE</h3>
<p>RLE stands for “run-length encoding”. RLE Gaussian Blur is best used on computer-generated images or those with large areas of constant intensity.</p>
</blockquote>
<p>and also</p>
<blockquote>
<p>They both produce the same results, but each one can be faster in some cases.</p>
</blockquote>
<p>So the short answer is that IIR is optimised for photographs, and RLE is optimised for images with areas of flat colour.</p>
<p>The claim seems to be that the only difference is the time taken to calculate the blur, and that the end results are identical. I haven't tested this, so if you need to rely on that claim you should test both and check for any differences in the results.</p>

CC BY-SA 3.0
2015-08-15T10:35:37.133Z
2015-08-15T10:35:37.133Z
2020-06-18T08:32:12.800Z
trichoplax is on Codidact now
<p>The Gimp has two different options in how you can perform Gaussian blur: "IIR" and "RLE".  What's the difference between them?</p>

CC BY-SA 3.0
2015-08-14T04:03:51.747Z
iir is likely "infinite impulse response" which is a type of filtering (the other being finite impulse response). Not sure what rle could stand for. It makes me think of "run length encoding" but I don't think that's what it stands for.
Alan Wolfe
CC BY-SA 3.0
2015-08-14T04:08:03.363Z
I guess I was right about rle but don't understand how it applies.  http://docs.gimp.org/en/plug-in-gauss.html
Alan Wolfe
CC BY-SA 3.0
2015-08-14T21:32:57.017Z
"RLE Gaussian Blur is best used on computer-generated images or those with large areas of constant intensity." Makes me think it's some kind of optimization of the blur process, that's somehow data-dependent so it works better on certain kinds of images? Is there any visible difference between the results of the two?
Nathan Reed
CC BY-SA 3.0
2015-08-15T04:18:03.440Z
This question seems very poorly formulated... You could have taken the time to do a quick search to at least get the definitions for the acronyms, since the previous commenters don't seem to know what they mean exactly.
glampert
<2d><gaussian-blur>
Different types of Gaussian blur?
Mark
# Different types of Gaussian blur?

(Asked by: username_0 on 2015-08-14)

The Gimp has two different options in how you can perform Gaussian blur: "IIR" and "RLE". What's the difference between them?

**Tags:** 2d, gaussian-blur

> **Comments:**
> **username_1**: iir is likely "infinite impulse response" which is a type of filtering (the other being finite impulse response). Not sure what rle could stand for. It makes me think of "run length encoding" but I don't think that's what it stands for.  
> **username_1**: I guess I was right about rle but don't understand how it applies.  http://docs.gimp.org/en/plug-in-gauss.html  
> **username_2**: "RLE Gaussian Blur is best used on computer-generated images or those with large areas of constant intensity." Makes me think it's some kind of optimization of the blur process, that's somehow data-dependent so it works better on certain kinds of images? Is there any visible difference between the results of the two?  
> **username_3**: This question seems very poorly formulated... You could have taken the time to do a quick search to at least get the definitions for the acronyms, since the previous commenters don't seem to know what they mean exactly.  

---

## 1 answers

### Answer by username_4 on 2015-08-15. Score: 5 | Accepted answer

From the [GIMP docs](http://docs.gimp.org/en/plug-in-gauss.html):

> ### IIR
>
> IIR stands for “infinite impulse response”. This blur works best for large radius values and for images which are not computer generated.
>
> ### RLE
>
> RLE stands for “run-length encoding”. RLE Gaussian Blur is best used on computer-generated images or those with large areas of constant intensity.

and also

> They both produce the same results, but each one can be faster in some cases.

So the short answer is that IIR is optimised for photographs, and RLE is optimised for images with areas of flat colour.

The claim seems to be that the only difference is the time taken to calculate the blur, and that the end results are identical. I haven't tested this, so if you need to rely on that claim you should test both and check for any differences in the results.


---

