• Overview of GIMP • List of GIMP tools I regularly use • Example of some quick simple edits on a sample image.
On Editing
Stable Diffusion is very powerful and can do a lot, but it will also make mistakes all the time. Often, I will have a render that I cannot make perfect, no matter how much I iterate and fine tune. This can be frustrating to spend so much time trying to improve on something, but making no meaningful progress.
This is where some basic image editing skills can become crucially useful. You don’t even need to be super good at it, since we can pass the edited image through img2img on low denoise to smooth out rough edits.
My general process • Make an initial upscaled render that is almost perfect (Image 1A, 1B) • Edit the render in GIMP to make rough fixes (Image 1C) • Process the edited image with img2img (Image 1D)
Kinds of things that I commonly edit • Adding/removing/extending/shortening fingers • Fixing/adding/replacing other body parts: including hands, teeth, eyes, genitals, nipples, bellybuttons, ears, noses • Removing unwanted background objects • Increasing amount of certain (ahem) bodily fluids • Color correction on clothes, fur, skin • Fixing horizontal alignment or perspective of background objects: including benches, fences, walls, buildings
GIMP
I use GIMP (GNU Image Manipulation Program) for all my editing, which is a free alternative to Photoshop. Download here https://www.gimp.org/
The GIMP user manual covers every aspect of the program in detail. My tutorial will mostly be guidance on what are the important things to focus on, and linking to the relevant parts of the manual.
There are lots of tools in the GIMP toolbox and menu, which can be overwhelming. What I’m doing here is listing just the tools that I regularly use. This is still kind of a large list, but this covers maybe 99% of everything I use in GIMP. Keyboard shortcuts are included.
(* Indicates an especially common or important tool that I use. If you only learn these, you will already have most of what you need for basic editing.)
Passing the edited image through img2img is an optional last step that I often do to smooth out my edits. Typically I do this with the same prompt, resolution, and settings as the original; but with as low a denoising strength as is possible. Usually the denoising I use is 0.05 or 0.1.
I find that this step also has a side effect of making the image more vibrant and sharp, especially with higher denoise. If this is undesirable for your style, you may consider using an inpainting mask to only process some parts of the image. This will be a topic for a future tutorial.
Images 2B and 2C show my A1111 settings to process the edited image 1B into the final render 1C. Here I use a denoise of 0.1.
Example Render and Edits
The attached images show a render of a couple foxes that I intentionally made with some noticeable mistakes and recorded a video of myself editing them in GIMP. Here I will go over the edits that were done and how I did them.
Attached “Video of GIMP editing” shows the entire editing process. Most of it is sped up, but you can see the edit history on the top right panel lists every action I am taking. The raw video was about 15 minutes.
First thing I do on any new edit is to lock the main layer, so that the original image is always there as the bottom layer. This is done by clicking the 3 buttons next to “Lock” in the layer view. Every edit happens in a new layer, usually made with the Rectangle tool to copy part of the original image.
Removing an extra finger
The female fox is waving with a hand that has 6 fingers.
Adding and removing fingers is probably the most common thing that I have to do. For removing a hand I usually end up just replacing it with background colors. I do that here with the Free Select and Smudge tools, which is how I usually remove things that are against a simple background.
However, this example is especially tricky because its an open hand where the palm under the finger also has to be edited. I could potentially just Smudge out the edge of the palm, but the lighting on there is important to keep in the image. So instead I take the uncommon step of using the Perspective tool on a Free Select of palm edge to align with the remaining fingers. This creates a new layer for the copied palm, which I use Eraser and Smudge to blend into the main hand. There’s still a bit of the original palm sticking out that I remove the same way I removed the finger.
Fixing background objects
There are several things to fix in background. On the top right, there’s a weird piece of a bench that I don’t want there. There’s what looks like a long patch of grass on the foot path. There’s a weird circular bump on a lamp post. On the center right, there’s a piece of path on the grass that I think shouldn’t be there.
All of these things can be fixed in a similar method as removing the finger. Since the backgrounds are mostly just grass and concrete, the Free Select and Smudge tools give me most of what I need to remove the parts that I don’t want there.
As I’m writing this, I am also noticing that parts of the main park bench don’t quite line up consistently. This is a common problem for me that I usually fix by replacing the bits of bench that don’t match. This can be easy to do since the bench planks are just brown rectangles with simple grass in the background.
Duplicating a hand
I want the image to have both foxes with their hands on the other’s shoulder. The male fox’s hand is missing.
Usually when I’m adding or replacing a body part like a hand, I usually copy it from another failed render. In this case, I am copying from within the same render. I’m making a copy of her hand to make his hand.
Usually, I will make a Rectangle copy of the thing I am copying and using Free Select to delete the outer edges of it. In this case, since it is a small object, I instead just use Free Select to copy the hand. After making the copy, the Flip tool is used to horizontally mirror the hand. Then the Perspective tool is used to reposition the hand and also make the proportions of the new hand slightly different. Additional uses of Free Select are used to remove parts obstructed by fur and her thumb. During that part, I temporarily change the opacity on the hand layer so that I can easily see what parts should be deleted.
The new hand needs better shadows to be more believable. I do this on a new layer created under the hand layer. Then I use Color Picker tool to select a dark part of the shirt, Pencil tool to roughly draw shadows under the hand, Smudge tool to make the shadow edges softer, and changing layer opacity to make the shadow transparent.
Once you have the basics down, in some ways editing can become the lazier approach. It can sometimes be so much easier to fix something simple like a missing/extra finger with editing than with the prompt.
Once you have the basics down, in some ways editing can become the lazier approach. It can sometimes
