Gimp

Raster manipulation tool.

Handy Bindings

<Tab> to toggle clear view (same in Tiled)
<Shift-b> for bucket (fill)
o for inkdropper tool
<Cmd-S-l> to convert a selection to a floating layer (drops down to the previous layer once moved with the mouse) to move it around
- <Cmd-h> drops the floating layer again
<Cmd-b> to view Toolbox
<Cmd-l> to view Layers
<S-e> for eraser
- Enable hard edge so that individual pixels can be erased cleanly. Also, set size to 1
<S-f> to flip a sprite
- Default is vertically
m to move a selection or layer
- By linking layers, they can be moved simultaneously (you can resize the layers to the canvas again after)
For the paintbrush tool, use p
Open up the toolbox with <Cmd-B>
Pencil tool can do hard-edge (n)
<E> for eraser
<Shift-o> for selecting by colour
r selecting by rectangle

Double click on a tool in the toolbox to open up tool options for it

Affected area fill can be toggled to fill whole selection/fill similar colours

Set threshold to 0 for pixel art

5 to zoom to 1600% (each pixel will be 2 * 2 grid)
1 to zoom to 100%
Configure the mouse wheel to zoom in and out in Gimp → Preference → Input Controllers → Zoom In/Zoom Out (https://www.linuxquestions.org/questions/linux-software-2/gimp-and-mouse-wheel-for-zoom-393728/)

Change size of canvas with Image → Canvas Size...
- Make sure you either create a new layer with the updated size, or resize the layer (rescale layer, layer to image size)
Configure the grid to be the number of pixels a tile takes up (Image → Configure Grid)
- Then, View → Show Grid to see it
Export with <Cmd-e>

If you cannot draw on a transparent area of a layer, make sure the alpha lock is turned off: http://www.gimpusers.com/forums/gimp-user/2184-cannot-paint-on-transparent-layer

This content has been automatically generated. For feedback or errata, please email eddie at xiaodi.li.