To remove shadows and grain from the background we can chose a threshold for values of transparency and of opacity when using the "Color to Alpha" tool in Gimp 2.10:
Simply drag the sliders until you are happy with the result. On a white background your image will then look like this:
Alternatively you can make a colour selection with the select by colour ...
You can clean the picture first, for instance using Levels:
the big peak on the right is the original background. This shows that the background is not pure white. If you use C2A without preprocessing, you have to aim for this color.
The white handle is dragged to the left (left edge of the background peak), so that most of the background becomes pure white....
You can't because the Tab is reserved for the GTK library (Gimp's UI is based on GTK). For some details see here.
This explains why you can't assign that combination in the keyboard shortcut editor, the editor doesn't see that key event when you enter it.
Even trying to bypass the editor and enter something like:
I believe the result you're looking for can be achieved with Lighting effects.
Following your steps up to the RGB noise, and then navigating to
Filters > Light and Shadow > Lighting effects
Within that menu turn on the Bump Map, then edit the material settings to your liking.
This quick mockup was made with Bump Mapping set to a Linear curve and Maximum ...
Use Filters > Map > Tile
Break the aspect ratio link icon so you can enter different values in the width and height independently.
Multiply the width and height by the number of images you want. Here I added *3 to the width, and *4 to the height - which calculates the tile size for 3 images across by 4 down.
Is there a way to change the guide units from relative to absolute when moving them on GIMP?
No need to, you already have the information:
And yes, even if you click slightly outside the guide, the values are corrected so that:
initial guide position + the offset (the values you circled) = actual guide position
Also is there a way to add a guide on ...
There is no way to flip non-parametric brushes.
The brush rotate options are only available on the "parametric" brushes (those that you can create with the brush editor). Since all these brushes have a symmetry you can achieve a flip by the suitable rotation.
There is no way to set keyboard shortcut to rotate non-parametric brushes.
You can set keyboard ...
The channels become grayed out whenever the image is not using the usual RGB mode (in other the words image is grayscale or color-indexed). To change the color mode, click "Image" -> "Mode" -> "RGB". Then you will be able to use the Curves tool to its full extent.
Anything "Auto" is not going to be the same on all images. So
you can accept that images are going to be transformed differently. This can be a good thing in some cases.
you want to apply the very same changes to all: you have to use an explicit/manual tool on the others (Levels/Curves...) but if you use an "auto" tool on the first, Gimp won't ...
Thanks for the update. As I suggested in my comment, separate motion blurs on different layers might work for you.
Duplicate the layers to be motion blurred, and apply motion blur separately to each, then blend the two using a layer blending mode - in the example I used "lighten only" but you could experiment with others.
Update: Another ...
Duplicate the layer
Make everything but the blue bars transparent in the upper layer:
Layer>Transparency>Add alpha channel
Color-select the white, and Delete
Color-select the grey lines, and Delete
Shift the top layer down by the width of the gaps
Not with paths directly, but with brushes certainly.
Click Windows > Dockable Dialogs > Symmetry Painting. Choose the symmetry you want, and paint. It is possible to create a path and then stroke it with a brush, and then the symmetry painting settings will apply.
If instead you want to create vector graphics, perhaps have a look at Inkscape. Like ...
When using bitmap files like PNG, it is always better to have a specialised program handle sizing. Though browsers have been much improved in this regard throughout the years, they are not as heavily optimised as specialised image handling programs such as Photoshop or GIMP.
Photoshop has a batch image resizer, which you can find under File > Scripts > ...
It looks like you are applying the gradient in one narrow horizontal strip.
You can apply the gradient to a wider strip, and you can shift the position of the stops while using the tool so it looks more like the example in the tutorial.
Here's the gradient I used
AFAIK there is no such thing in Gimp. Given the result, it seems equivalent in Gimp to
Stroke the edges with a paint brush set to 20% opacity
Stroke the edges ("Line" mode, or brush at 100% opacity) on an additional layer, set to 20% opacity.
To recreate the image below:
Tool: Paint brush, Hardness 100 brush,pure white,
The solution is to use a newer version of GIMP! The UI of the tool has been updated. (And all the keyboard shortcuts mentioned in the question also work).
*Aside: The source code I reference in the question is of the latest GIMP version at time of writing. Looking at the source code appropriate to my old version of GIMP, the "step backwards one frame" ...
Make sure you have installed the gimp-python package, which has become "optional" in recent Ubuntu releases.
The message you see above is normal, the python code imports modules that are only available when the plugin is called by Gimp.
If you want to routinely cut an image using guides (always the same positions?) and save the results, I 'll suggest:
ofn-preset-guides. This lets you define set(s) of guides that you can add to your image (with a single keystroke if you define a shortcut).
ofn-layer-guillotine: works like "Slice using guides", but slices a layer into multiple layers