mirror of
https://github.com/gbdev/rgbds.git
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8c62e80c18
Currently missing from the old version:
- `-f` ("fixing" the input image to be indexed)
- `-m` (the code for detecting mirrored tiles is missing, but all of the
"plumbing" is otherwise there)
- `-C`
- `-d`
- `-x` (though I need to check the exact functionality the old one has)
- Also the man page is still a draft and needs to be fleshed out
More planned features are not implemented yet either:
- Explicit palette spec
- Better error messages, also error "images"
- Better 8x16 support, as well as other "dedup unit" sizes
- Support for arbitrary number of palettes & colors per palette
- Other output formats (for example, a "full" palette map for "streaming"
use cases like gb-open-world)
- Quantization?
Some things may also be bugged:
- Transparency support
- Tile offsets (not exposed yet)
- Tile counts per bank (not exposed yet)
...and performance remains to be checked.
We need to set up some tests, honestly.
177 lines
6.6 KiB
Groff
177 lines
6.6 KiB
Groff
.\"
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.\" This file is part of RGBDS.
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.\"
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.\" Copyright (c) 2013-2021, stag019 and RGBDS contributors.
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.\"
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.\" SPDX-License-Identifier: MIT
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.\"
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.Dd March 28, 2021
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.Dt RGBGFX 1
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.Os
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.Sh NAME
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.Nm rgbgfx
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.Nd Game Boy graphics converter
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.Sh SYNOPSIS
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.Nm
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.Op Fl CDhmuVv
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.Op Fl f | Fl F
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.Op Fl a Ar attrmap | Fl A
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.Op Fl d Ar depth
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.Op Fl o Ar out_file
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.Op Fl p Ar pal_file | Fl P
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.Op Fl t Ar tilemap | Fl T
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.Op Fl x Ar tiles
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.Ar file
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.Sh DESCRIPTION
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The
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.Nm
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program converts PNG images into data suitable
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.Sh ARGUMENTS
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Note that options can be abbreviated as long as the abbreviation is unambiguous:
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.Fl Fl verb
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is
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.Fl Fl verbose ,
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but
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.Fl Fl ver
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is invalid because it could also be
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.Fl Fl version .
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The arguments are as follows:
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.Bl -tag -width Ds
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.It Fl a Ar attrmap , Fl Fl attr-map Ar attrmap
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Generate a file of tile mirroring attributes for OAM or (CGB-only) background tiles.
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For each tile in the input file, a byte is written representing the dimensions that the associated tile in the output file should be mirrored.
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Useful in combination with
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.Fl m
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to keep track the mirror direction of mirrored duplicate tiles.
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.It Fl A , Fl Fl output-attr-map
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Same as
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.Fl a ,
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but the attrmap file output name is made by taking the input filename, removing the file extension, and appending
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.Pa .attrmap .
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.It Fl C , Fl Fl color-curve
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Use the color curve of the Game Boy Color when generating palettes.
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.It Fl D , Fl Fl debug
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Debug features are enabled.
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.It Fl d Ar depth , Fl Fl depth Ar depth
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The bit depth of the output image (either 1 or 2).
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By default, the bit depth is 2 (two bits per pixel).
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.It Fl f , Fl Fl fix
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Fix the input PNG file to be a correctly indexed image.
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.It Fl F , Fl Fl fix-and-save
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Same as
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.Fl f ,
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but additionally, the supplied command line parameters are saved within the PNG and will be loaded and automatically used next time.
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.It Fl h , Fl Fl horizontal
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Lay out tiles in column-major order (column by column), instead of the default row-major order (line by line).
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Especially useful for "8x16" OBJ mode, if the input image is 16 pixels tall.
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.It Fl m , Fl Fl mirror-tiles
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Truncate tiles by checking for tiles that are mirrored versions of others and omitting these from the output file.
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Useful with tilemaps and attrmaps together to keep track of the duplicated tiles and the dimension mirrored.
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Tiles are checked for horizontal, vertical, and horizontal-vertical mirroring.
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Implies
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.Fl u .
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.It Fl o Ar out_file , Fl Fl output Ar out_file
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The name of the output file.
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.It Fl p Ar pal_file , Fl Fl palette Ar pal_file
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Output the image's palette in standard GBC palette format: bytes (8 bytes for two bits per pixel, 4 bytes for one bit per pixel) containing the RGB15 values in little-endian byte order.
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If the palette contains too few colors, the remaining entries are set to black.
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.It Fl P , Fl Fl output-palette
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Same as
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.Fl p ,
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but the palette file output name is made by taking the input PNG file's filename, removing the file extension, and appending
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.Pa .pal .
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.It Fl t Ar tilemap , Fl Fl tilemap Ar tilemap
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Generate a file of tile indices.
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For each tile in the input file, a byte is written representing the index of the associated tile in the output file.
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Useful in combination with
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.Fl u
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or
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.Fl m
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to keep track of duplicate tiles.
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.It Fl T , Fl Fl output-tilemap
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Same as
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.Fl t ,
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but the tilemap file output name is made by taking the input filename, removing the file extension, and appending
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.Pa .tilemap .
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.It Fl u , Fl Fl unique-tiles
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Truncate tiles by checking for tiles that are exact duplicates of others and omitting these from the output file.
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Useful with tilemaps to keep track of the duplicated tiles.
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.It Fl V , Fl Fl version
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Print the version of the program and exit.
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.It Fl v , Fl Fl verbose
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Verbose.
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Print errors when the command line parameters and the parameters in the PNG file don't match.
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.It Fl x Ar amount , Fl Fl trim-end Ar amount
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Trim the end of the output file by this many tiles.
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.Pq TODO: tiles, or tilemap?
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.El
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.Sh PALETTE GENERATION
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.Nm
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must decide in which order to place colors in the palettes, but the input PNG usually lacks any indications.
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A lot of the time, the order does not matter; however, sometimes it does, and
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.Nm
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attempts to account for those cases.
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.Bl -bullet -offset indent
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.It
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First, if the image contains
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.Em any
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transparent pixel, color #0 of
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.Em all
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palettes will be allocated to it.
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If palettes were explicitly specified using
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.Fl TODO ,
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then they will specify color #1 onwards.
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.Pq If you do not want this, ask your image editor to remove the alpha channel.
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.It
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If the PNG file internally contains a palette (often dubbed an
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.Dq indexed
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PNG), then colors in each output palette will be sorted according to their order in the PNG's palette.
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Any unused entries will be ignored, and only the first entry is considered if there any duplicates.
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.Pq If you want a given color to appear more than once in a palette, you should specify the palettes explicitly instead using Fl TODO .
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.It
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Otherwise, if the PNG only contains shades of gray, they will be categorized into 4
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.Dq bins
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.Pq white, light gray, dark gray, and black in this order ,
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and the palette is set to these four bins.
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(TODO: how does this interact with 1bpp? With more than 1 palette?)
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If more than one grey ends up in the same bin, the RGB method below is used instead.
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.It
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If none of the above apply, colors are sorted from lightest to darkest.
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(This is what the old documentation claimed, but the definition of luminance that was used wasn't quite right.
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It is kept for compatibility.)
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.El
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.Pp
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Note that the
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.Dq indexed
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behavior depends on an internal detail of how the PNG is saved.
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Since few image editors (such as GIMP) expose that detail, this behavior is only kept for compatibility and should be considered deprecated; if the order of colors in the palettes is important to you, please use
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.Fl TODO
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to specify the palette explicitly.
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.Sh OUTPUT FILES
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.Ss Palette data
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Palette data is output like a dump of GBC palette memory: the output is a binary file.
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Each color is written as GBC-native little-endian RGB555 (that is, the first byte contains the red and the lower 3 bits of green).
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There is no padding between colors, nor between palettes; however, empty colors in the palettes are filled as 0xFF bytes.
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.Sh EXAMPLES
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The following will only validate the PNG [...] but output nothing:
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.Pp
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.D1 $ rgbgfx in.png
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.Sh BUGS
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Please report bugs on
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.Lk https://github.com/gbdev/rgbds/issues GitHub .
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.Sh SEE ALSO
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.Xr rgbds 7 ,
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.Xr rgbasm 1 ,
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.Xr rgblink 1 ,
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.Xr rgbfix 1 ,
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.Xr gbz80 7
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.Sh HISTORY
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.Nm
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was originally created by
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.An stag019
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to be included in RGBDS.
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It was later rewritten by
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.An ISSOtm ,
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and is now maintained by a number of contributors at
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.Lk https://github.com/gbdev/rgbds .
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