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GbReaper

Last update: Thu Jun 5 22:25:41 2025

GbReaper : a Game boy ROM viewer, sprite and map editor

I'm playing with GB now and though you can use multiple tools to do the job, it's a pain. So I'm making this easier with a all in one tool. All exist as free software, usually with source code but in "old" languages (Delphi 3!) and no more maintained.
- ROM viewer: replace GB tile viewer
- Sprite editor: replace GBSP
- Map editor: replace GBMP
(2020 March) Now maybe 5 years later I wonder why I started that, other than "because I can" and that damned not-invented-here syndrom. Anyway it's covering enough of what I need, and if by chance it helps someone someday I'll be happy.
(2022 August) Still wondering but resumed developping it! Moved it to its own repo also.

So in case you are not like me and don't want to reinvent the wheel use the old-yet-working:

GameBoy Tile Designer

GameBoy Map Designer

Specifications

✔ = done, otherwise it's a TODO

ROM

See a GB ROM content ✔

Extract one sprite to the library ✔

Extract 2/4 consecutive sprites (most of them are 4x4 anyway) with Ctrl

Set a palette △ (disabled for now)

Page up/down + mouse scroll △ (Page up/down ok)

Slight vertical misalignement on large ROM to be fixed

Library

Reorder library

Delete sprite from library

Duplicate sprite from library

Group some sprites by 4 visually

Categories : background, characters, items, custom, ...

Fold categories

Sprites

Create new sprite in library ✔

See a 3x3 map of the sprite ✔

See a zoom x1, x2 and x4 of the sprite ✔

Real time update of everything when updating a sprite ✔

Edit sprite: pen ✔

Edit sprite: fill, Mirror L/R T/B, negative, rotate, rotate palette

See each one palette

In and out

Save & load to file ✔

Export to C code to be built by GBDK-n or the old GBDK: nb elements const and each element start index ✔

Import and image and transform to sprites on the fly New! ✔

Import 4 tile at a time with Ctrl ✔

Better algorithm than closest neighbor for Tilizator: dither

Export also makes a makefile

Export can choose which map(s)

Export can save space by skipping unused tiles

Maps

Create new map, delete map, edit map ✔

Map editor: use sprite and tool paint/fill ✔

Paint with 4 consecutive sprites (most characters are 2x2) with Ctrl ✔

Fill paint with 2 consecutive alternate sprites (for backgrounds)

Highlight hover on map

Duplicate map

Code

Source

C# on .NET 4.0 (use Visual Studio 2010 Express it's free) and runs on Windows, not on Mono (alas, at least not yet).
As usual on Git https://github.com/AlanFromJapan/GBReaper

You can compile it with GBDK-n or the old GBDK.

Compilation

Ok so everybody complains about the old GBDK and ...yeah honestly, it's pretty bad. Took me 2 days to end up with bugs on code that I knew was sound (been a coder for 25 years, I know my C).

Solution 1: use GBDK-n, better but my Mint 19 sdcc is 3.5 and sometimes compilation take minutes to complete!

Solution 2: use GBDK-n AND the latest sdcc 4.0. You need to edit the gbdk-n compile script to use the right sdcc, and you get nice compilation under a handful of seconds.

Solution 3: go ASM

In all cases, that code ended working as planned with a recent compiler.

Projects

On GitHub, on my GameBoy repository.

Pictures

Basic screen, with a ROM loaded and a project with 2 maps loaded.

The same map loaded on a ROM and in a GB v(^_^)v.

All content on this site is shared under the MIT licence (do what u want, don't sue me, hat tip appreciated)
electrogeek.tokyo ~ Formerly known as Kalshagar.wikispaces.com and electrogeek.cc (AlanFromJapan [2009 - 2025])