How to change recurring pattern across image in Gimp?

Question

I have this image in Gimp:

Each red square has the same width, height, color and layer.

I want to make all red squares half blue like this:

To do this I'd make the first square half blue then copy and paste the new square to all the other red squares in the image.

Although what if there's 30 squares, copying and pasting over each square would take ages.

Does Gimp have a way that I can just change the first square and it copies the same change to all the other squares in the image?

Thanks

Answer 1

Although it's possible to use GIMP to create work like this manually by copying and pasting, it's not the best kind of software to use for this.

Use Inskcape instead. It's a vector image editor, and it's free and open source like GIMP. It has a feature called "clones" which could solve your problem. This is very similar to what is sometimes called "symbols" in other software. Anyway, here are the basic steps to set it up.

1. Draw two rectangles butted up against each other, fill each with any colour you want, group them, and clone the group. Move the clone away from it's source (it's automatically created directly on top of the source).

2. Copy and paste the clone as many times as you want.

3. Select a rectangle in the clone source, change the fill and all the clone copies will update automatically

Example

Answer 2

No magic bullet AFAIK, but no need to copy/paste.

Worst case, if the square positions are random:

1. Make a first square as you wish
2. Select and copy this square to the clipboard
3. Start the paint brush oe pencil and set it to clipboard (this is always the first in the list)
4. Paint all remaining squares with a single click on each. If necessary lock the alpha to avoid painting outside of the existing squares.

If the blue parts do not vertically overlap any red parts, you can make vertical strip selections that cover the blue parts, lock the alpha, and bucket-fill the selection.