Sprite / Icon bank

A Sprite bank (AmSp) holds sprites used with the SPRITE command; an Icon bank (AmIc) holds bobs used with the BOB command. Both use the same file format and share a 32-entry Amiga colour palette.

Sprites/icons are always in chip RAM. The bank number is fixed: sprite banks are always bank 1, icon banks always bank 2.

Commands

# Export to JSON + PNG sprite sheet
portamos disasm Sprites.Abk output/sprites.json

# Export with IFF ILBM sprite sheet instead of PNG
portamos disasm --ilbm Sprites.Abk output/sprites.json

# Reassemble
portamos asm output/sprites.json Sprites.Abk

JSON schema

{
  "type": "Sprite",
  "spritesheet": "sprites.png",
  "numColours": 16,
  "palette": [
    "#000000", "#ffffff", "#ff0000", "#00ff00"
  ],
  "sprites": [
    {
      "index": 0,
      "x": 0,
      "y": 0,
      "width": 16,
      "height": 16,
      "planes": 4,
      "hotspotX": 8,
      "hotspotY": 8
    },
    {
      "index": 1,
      "empty": true
    }
  ]
}

Field reference

Top level

Field	Type	Description
type	string	"Sprite" or "Icon"
spritesheet	string	Path to PNG or IFF image file relative to the JSON
numColours	integer	Number of colours in the palette (1 << planes)
palette	array of strings	32 hex RGB colours ("#rrggbb")

sprites[]

Field	Type	Description
index	integer	Sprite number within the bank (0-based)
empty	boolean	true for empty/placeholder slots
x	integer	X offset within the sprite sheet in pixels
y	integer	Y offset within the sprite sheet in pixels
width	integer	Width in pixels (always a multiple of 16)
height	integer	Height in pixels
planes	integer	Colour depth in bitplanes (1–6)
hotspotX	integer	Hot-spot X coordinate; omitted when 0
hotspotY	integer	Hot-spot Y coordinate; omitted when 0

Sprite sheet layout

Sprites are composited into a grid. The cell size is determined by the largest sprite in the bank. Non-empty sprites fill left-to-right, top-to-bottom. Empty slots are not placed in the grid.

The importer reads each sprite’s rectangle from the sheet using x, y, width, and height. You can rearrange sprites in an image editor as long as you update the coordinates in the JSON to match.