Basic GIMP Usage Guide (it has layers, like onion knights)

[Tersius]

I decided to write this guide up to help all the new users that don't have much knowledge about using image editing tools.  As the title suggests, this guide is focused on giving basic instructions for overcoming the learning curve associated with GIMP.

Gimp can be downloaded for free (it's legal!) here:
http://gimp.org/downloads/

* Note:  Whenever I mention a tool, I will specify it's hotkey in parenthesis.  Example:  Eraser (Shift + e).  This means if you hold down shift and press e while your image window is the active window (yes, I know this requirement is very frustrating), the eraser tool will become the active tool.  Also note that hovering the mouse over a specific tool should tell you the hotkey you need to use to activate it.  Some tools have extra functionality when you hold down shift, alt, or ctrl while clicking, I will highlight some of that functionality.

Setting Up
Every time I fire GIMP up to work on sprites, there are a few settings I have to change (if anyone knows how to make GIMP default to these I would greatly appreciate the tip!).  This setup is to make two of my tools behave properly for sprites, and to pull up two dialogs I use extensively in editing.

The first of the tools is the Pencil (n).  When it is active click on the black circle to the right of brush and select the tiniest dot you see (should be to the left of the select brush).  I find it easier to work on sprites with a 1x1 brush.  The next tool is the eraser (Shift + e).  Make sure Hard Edge is checked.

The dialogs I open can be found by clicking Dialogs (it's the second to rightmost menu option on the top of the window your image is in.  Make sure the window is large enough to see all the menu items), then "Colormap", and by clicking Dialogs again, followed by "Layers."  These handy dialogs make editing sprites in GIMP so much easier and are the reason GIMP is my main image editing program.  Next I will explain how to use these dialogs.

The Colormap
The colormap is the color palette for the sprite you are working on.  When you are making changes to a sprite, be sure to only use the first 16 colors (numbered 0 - 15 on the colormap), or you will get an error when you try to import it into ShiShi and your sprite will look "funky" when you use it in the game.  If you want a different color than is on one of the first 16, double click on one of them and select your color.  Note that all parts of the sprite that used the old color will be changed to use the new color.  This allows for simple "repaletting" of sprites, such as changing a sprite's hair from blond to puke green.  

It is important to realize that the first color (#0) is always treated as "invisible" by the game.  By default this color is shown in GIMP as black.  If you want your sprite to be black in the game, you will need to change one of the other colors to black.  If you right click on the colormap, you can also do some options to import other colormaps (or palettes) into the active image.  While this is a very handy technique, it is beyond the scope of this post.

Layers
Layers are a very useful tool for "trying things out" on a sprite.  Layers could be viewed as a slightly more advanced topic, but don't let that stop you from using them as they are very powerful!  They go somewhere along the lines of with great power comes great responsibility...

In order to use layers properly, you need to know a little bit about file types in GIMP.  The default GIMP file type is a .xcf.  If you want layers you create to be saved you have to save your sprite as a .xcf.  However, you cannot import .xcf files into FFT.  To do that, you must save the image as a .bmp.  When you try to save an image that has layers in a .bmp format, GIMP will prompt you with some options about exporting the image.  I always choose to "merge visible layers".  I'll tell you why you should use this option when I explain the usage of layers.  Another useful file format is .png.  If you post a .png image in this forum, that image will show up in the body of your post.

As I mentioned earlier, layers are very useful for "trying things out" on your sprite.  An image with multiple layers could be thought of as multiple images stacked on top of each other.  Any layers that are on top the of list will also be on top of the stack.  When you draw something on a layer, it will obscure everything in that spot for all the layers below that layer.  Because of this, I like to have the "Background" layer (this is the default layer name for the "only layer" that exists in a .bmp) on the bottom, and make my sprite changes on layers that I place above that.

If layers seem confusing to you, think of them in terms of painting.  The background is the first coat of paint you put on.  Then as you go up the "layer list", you go through the subsequent layers of paint.  Whenever you "miss a spot" when painting, you will see the previous coat of paint showing through.

In the layer dialog, you may notice little "eye" icons next to the layer names.  Clicking on those icons will turn that layer invisible.  Any layers that are invisible when you save a .bmp image and choose "Merge Visible Layers" will not be "drawn into" the bitmap.  This is where layers are useful for "trying things out."  I will illustrate this technique through an example:

Lets say I want to draw a new logo over the logo on the back of the knight's cape.  First I would open my the spritesheet I exported using ShiShi (let's call it knight.bmp).  Because I plan on using layers, I immediately save it as knight.xcf.  Next, I create a new layer and call it logo.  I then highlight that layer and begin painting the new logo to my heart's content.  As long as the "logo" layer is above the "background" layer, the logo will be drawn on top of the "default" logo.  When I am done drawing the logo in all of the proper spots (and at various times during my drawing), I save my sprite as knight.xcf.  Then I save it as knight.bmp so I import it into the game:  Import into ShiShi, recompile into my ISO of choice, and SUCCESS! My knight now has logo awesomeness.

Now let's say get tired of my logo, but I don't really want to delete it outright.  If I only had the bmp version of the logo, I would have to backup the bitmap before making my new change.  However, with my .xcf file I can harness the power and speed of layers.  After opening my "knight.xcf", I click on the eye icon in the left part of the "logo" layer.  My logo disappears!  But all that work is not lost, clicking on the eye brings it right back.  I decide to get to work, and click on the eye icon one more time to hide the logo.  Then I create a new layer and call it "cool logo 2" (or some other creative and descriptive name).  Then, just like the first logo, I go to work painting my new logo.  When I finish up, as long as the first custom logo is still invisible, and the second logo is visible, I can export my .bmp and test for logo awesomeness (don't forget to save the file as .xcf as well in case you need that in the future.)

I like to use layers for more than just creating logos.  When I have multiple hairstyles or outfits I want to try on my sprite (geese that makes me sound like a girl dressing up dolls), I do a quick, single pose mockup using multiple layers and toggle through the layers to see which clothing / hair combination I like.  I also rarely delete a layer in case I want to refer to a previous idea.  Other times, the hair may not quite look right, but I won't know if I should make it longer or shorter.  To test this, I'll create a layer called "longer" and draw the longer hair in.  I then create a layer called "shoter" and use color #0 (FFT's transparent color, but GIMP's very opaque, black color) to "give my sprite a hair cut".  By hiding and showing the two layers I can decide which style I like the most.

Tools List
OK, if you've followed so far, you've been reading for quite a while and by now are probably getting anxious to move on to something else (I know I am).  Fortunately, all I have left for now is a list of the tools I use, their hotkeys, and a few simple tricks.

Pencil Tool (n). Used to color your sprite.  If you hold down ctrl while the pencil tool is active, it becomes the eye dropper tool and "picks up color".  Note that the active color is highlighted in the colormap.  After clicking once on the image, you can hold down shift to draw a straight line (also works with the eraser tool).

Eraser Tool (Shift + E). Used to erase areas.  On upper layers, this means the "painted section" is turned transparent.  I don't remember exactly what it does on the "background" layer (I use the pencil tool + color #0 for erasing there).

Free Select Tool (f). AKA Lasso tool.  Is used to select areas in your image for copy (ctrl + c) / cut (ctrl + x) and paste(ctrl + v).  After pasting, clicking and dragging inside the "selected region" will allow you to move it, and clicking out the selected region will "anchor" (I think of it as make permanent) the selection to the active layer.  Pressing del while an area is selected erases it.  Holding Shift allows you to add to the selection, holding ctrl allows you to subtract from the selection.  Selection is also useful when using the paint bucket tool.

Color picker (Shift + O).  Selects all pixels in the active layer that have the exact same color value (this can be modified in the color picker options) as the clicked pixel.  This is useful when used in conjunction with the paint bucket tool.  Make sure you "deselect" the portrait section before painting over an entire color.  Not doing so may cause undesired results.

Paint Bucket Tool (Shift + B). Used to fill entire sections with a specific color.  The paint bucket tool options can be used to toggle between filling the entire selection, or filling only similar colors in the clicked region.

Magnifying Lense (z).  Used to zoom in on a point in the image.  Can also be used to zoom in on a specific region by click + dragging and drawing a rectangle around the area of interest.  Holding down ctrl, reverses the lens so that clicking will zoom out instead of zoom in.

The End
Well that's it for now.  I hope at least a few people find this guide useful for cracking open GIMP.  Happy spriting!

[Tersius]

Reserved in the unlikely event that I wish to expand on this.