Gimp Script Showcase: Warming and Cooling Filter

June 5, 2010
A photo edited with the filter discussed below.  f/4.0; 1/320sec; 105mm; ISO 200

A photo edited with the filter discussed below. f/4.0; 1/320sec; 105mm; ISO 200

I’ve talked about using solid color layers to warm or cool your photos, but there’s also a Gimp script out there if you’re not interested in going the Do-It-Yourself route. Plus it offers a few more options than just simple solid-color layers do. You can find the script here. Once again, if you need to know how to install Gimp Scripts, go on back to this entry.

Once you install this warming and cooling filter, you’ll find it under Colors –> Warming or Cooling Filter.

Let’s take a look at the options for this Script:

Options

The Tone drop-down has 7 options:

  • Cooling – Wratten 80
  • Cooling – Wratten 82
  • Warming – Wratten 81
  • Warming – Wratten 85
  • Roy’s Warm
  • Brauer’s Warm
  • Pasty Cadaveric Look

The Overlay Fill Method only applies to the Wratten Filters, so I’ll talk about it when I go over those. The Opacity slider, I’m sure you’re all aware of what I’ll say about that one: there’s no need to mess with it because it’s easily changed after-the-fact.

And finally, the Flatten Image checkbox will – surprisingly enough – flatten your image after running the script. Flattening an image means that it will basically remove all the layers you were working with and instead give you one layer of what was visible. So any new layers created while running this script and any layers you already had in your image will no longer be there for you to play with. I never check this box on any script I run, because as soon as you do that, the only way you can manipulate or undo any part of the filter is to do an Edit –> Undo and remove the entire filter itself.

The Wratten Filters

The basics of these filters really build off of what my previous entry was talking about – using solid colored layers to warm or cool your photos. If we don’t mess with the Overly Fill Method dropdown and just run each of the four Wratten filters, you’ll get four different solid color layers, set to Overlay and set at 25% Opacity:

Wratten Colors

Nothing special is happening, nothing changed to my Background layer, running the filter just gives you a solid color layer set to overlay. Obviously this is something that’s done easy enough without using a script, but sometimes it’s just nice to click a button and have it do it for you instead of creating your layer and picking your fill color and setting the blend mode (what? I’m lazy sometimes. I’ll admit it.). At 25% opacity, the change was pretty subtle, so to make sure you could really see the difference in the photos, I bumped it up to 50%. Here’s what those lovely colored layers do to an image of a flower (top half is the original photo, bottom half is with the Wratten Filter):

Cooling - Wratten 80

Cooling - Wratten 80

Cooling - Wratten 82

Cooling - Wratten 82

Warming - Wratten 81

Warming - Wratten 81

Warming - Wratten 85

Warming - Wratten 85

Now that we know what all the colors are and how much they warm or cool a photo, let’s look at the next drop down for the Fill Method. If you go back to the page in the Gimp plugin registry, you’ll see that it explains that selecting the Fill Red Channel, it will select only the red channel of your image and apply the color to that – suggesting that this is good for warming or cooling skin tone without effecting the entire image.

So, let’s start with this (unedited) photo of my niece:

Unedited

Unedited

If I run Warming – Wratten 81 with the Fill Red Channel option selected, I get a new layer created that looks like this (note, the script doesn’t actually look like this when it runs, because this layer is set to Overlay and 25% opacity. But I switched it to normal and 100% opacity in order to show you what the layer itself looked like):

100% Opacity, Normal blend mode

100% Opacity, Normal blend mode

Notice that her purple shirt and the dark parts of the green grass are almost all black, so they’re not going to get as warmed up as they would if I was running the script with Fill Entire Layer selected. I ran the script twice – once with Fill Red Channel and once with Fill Entire Layer (and kept them both at overlay – I think I might have bumped the opacity up to 50%, too, but I didn’t seem to write that down. Oops.). Here they are, side-by-side for a comparison:

Fill Entire on the left and Fill Red on the right

Fill Entire on the left and Fill Red on the right

You can really tell the difference by looking at the trees in the background that are getting quite yellow-y in the Fill Entire Layer version of the image. It’s a very helpful tool. The only thing I don’t really like is that, because the non-colored part of the Fill Red Channel layer is so dark, and the layer is set to overlay, it makes parts of the photo – like the shadows, her hair, and her shirt – quite dark.

Roy’s Warm

If you go back to the registry page for the filter, you’ll see that it says the Roy’s Warm option uses teh color balance to adjust the magenta and yellow hues in order to warm up the image. From my limited experience, I can tell you a few things about this option:

  • You don’t have to bother with the Fill Mode dropdown (since that only applies for the Wratten options anyway)
  • The Opacity slider makes no difference even if you wanted to use it, because it doesn’t create a second layer…
  • …which is why I suggest creating a duplicate layer before using this option, if only to make it easier to compare before and after by just making the second layer visible and invisible
  • It made such a little difference on some of my photos that it wasn’t even noticable. For instance, on the flower photo I was using in the Wratten examples, you could barely tell anything changed, even when switching the visibility on the layer

It did, however, make a slight difference on this photo of a dandelion next to a river. Original, unedited photo is on the left, Roy’s Warm is on the right:

Roy's Warm

Roy's Warm

Brauer’s Warm

Once again, we can look at what it says on the registry page to know that a duplicate layer is already going to be created for us, and the hue of this layer is going to be adjusted.

The opacity slider does make a difference on this one (though I still say no reason to bother messing with it until after you run the script so you can adjust it while actually looking at the photo). What you’re going to get is a rather sepia-looking version of your photo with the blend mode set to Normal. For instance, if you run it on the original flower photo and set the opacity to 100%, this is what you get:

100% Opacity

100% Opacity

If you drop the opacity down to the default of 25%, you get this (unedited on top, Brauer on the bottom):

Brauer's Warm

Brauer's Warm

I had a lot of fun playing with this one, too, and really liked switching the blend mode to Overlay and bumping the opacity back up to 100% (once again, unedited on top):

Blend mode set to overlay at 100%

Blend mode set to overlay at 100%

It’s not quite as much of a “warming” effect, per se, but it does look kinda cool, in my opinion.

Pasty Cadaveric Look

As the name suggests, this is supposed to “cool” the skin tones and give a person a pasty cadaver-like look. I ran this on the photo of my niece, and it definitely did what it said it would do, but I can’t say I actually like it (sorry, I didn’t split this one into unedited and edited, I apologize):

Pasty

Pasty

But, then I tried it on the flower picture, just to see how it looked on a non-person, and ooooh, I liked it! (As usual, unedited on top):

Pasty flower

Pasty flower

Conclusion

I’m really loving this script – which in a way seems surprising because it’s all things that are relatively easy to do without a script, but it’s just kinda nice to have a script do it all for you, and have a bunch of warming and cooling options all tucked away in one place, so if you KNOW you want to warm up your photo, you can just try them all and see what looks best in a matter of a few minutes. Which reminds me of something else I really liked about this script – it ran really fast. I realize that’s directly related to the fact that it’s doing relatively simple things. But still, it’s definitely nice.

As a final thought, I did want to mention that, if you’re shooting in RAW, you also have the option of changing the white balance of your photo in order to warm or cool the image. I talk about using the Temperature slider – among other things – in UFRaw in this post.

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  • Alma

    Very good tutorial, thanks!

  • These are such helpful, useful, interesting and relevant posts. I would never have known GIMP scripts existed without them and now I am much more brave about editing photos. Tutorial posts are a lot of work, too, so many thanks!

  • Great Article. This will save me some time. Going to try this out of a few of my photos.
    Thanks,

  • Thank you for pointing this one out. I've been frustrated with doing it 'manually' and not getting what I want and this will help, especially being able to adjust the opacity.
    Jeff

  • kensley

    Good tutorial. A similar technique for warming up photos in gimp is simply duplicating the photo layer - set the top image to a layer effect of 'overlay'. On that same layer click on color->curves. From that point adjust your value points and your red blue green color points (all 3) to give you rich effects!

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