CreatingShieldIconsInGimp

This is a quick summary of how I created two segment shield icons for the HUD.

I'm writing this down so I remember how to do this, because me not being an artist, it took me ages to figure out how to do this and I don't want to go through the frustration of rediscovering it!!!!

Programs I used:

• GIMP 2.8
• apngasm 3.1.6

Create Ship Image

1. (if necessary) create a new canvas 112x93
2. Import a top down image of the ship & centre it
   • so far I've grabbed the existing shield anim frame 0
   • might be able to grab other ships by
     1. setting shield anim to be FSO generated
     2. DISABLING shields (or the auto-generated shield bars may overlap the image)
     3. screenshot'ing the HUD
     4. converting the image to greyscale (TBC how best to do this!)

Create Shield

1. Using fuzzy select (with zero threshold) select the area outside the ship image; then invert selection
   • If necessary modify the selection to better fit the ship, e.g. using the oval select (additive) to round out an irregular shape
2. Select -> Grow... by 10 (? try 11) pixels
3. Select -> feather set to 2 pixels
4. Create new layer (black background) & select the new layer
5. Bucket fill: white
6. Select -> Shrink... by 3 (?) pixels
7. Bucket fill: black (leaving a mostly 1 pixel full-white outline)
8. Select -> Grow... by 2 pixels
9. Filters -> Blur -> Gaussian blur; aspect locked; 3 (?) pixels
10. Filters -> Artistic -> Softglow; 9 (?) pixels
11. Use colour select to select all the fully black regions (outside & inside shield); then invert selection
12. Layer -> Mask -> Add Layer Mask... using the current selection
13. Confirm you can clearly see the ship and the shields don't overlap the ship (unless you really want them to!)

Split Shield into Segments

1. through the middle of the oval; create rectangle selection 2 pixels high & shield width, then fill full black
2. at the end of each shield (4x ends) create rectangle selection, 2 pixels high & shield width
   • should have 4x small rectangles
   • might need to be done in two steps? fore/aft ends?
3. apply the gaussian blur filter (1 pixel, width & height locked)
4. create a new layer and move fore or aft to it (should have 3x layers)
5. export image (all layers) as png
6. use apngasm to create APNG image
   • apngasm -o shipname_shield.png ship_base.png ship_shield_fore.png ship_shield_aft.png
7. test in FSO

WASH, RINSE, REPEAT

TODO: figure out if there's any benefit to creating an ani instead of an apng (maybe uses less ram/texture memory? since apngs auto-expand to full 24bits per pixel?)