Retro Graphics Toolkit is a GPLv3 or later licensed open source graphics editor that stores truecolor information in addition to regular tiles. This allows for non destructive editing of palettes. When the palette is changed the tiles can be dithered to fit the new palette. With Retro Graphics Toolkit you can save palettes, tiles, tilemaps, sprites and levels for the Sega Genesis, NES, Master System and Game Gear. Support for more systems is planed for future versions. The best way to get started With Retro Graphics Toolkit is to read the wiki https://github.com/ComputerNerd/Retro-Graphics-Toolkit/wiki Although there is nothing special about the format outputted by Retro Graphics Toolkit (complying with existing formats for the system is one of my goals). I do provide examples currently for the Sega Genesis, NES, Master System and Game Gear. https://github.com/ComputerNerd/Retro-Graphics-Toolkit/tree/master/examples Screenshots: The plane editor is what you will be using when importing an image and displaying on the game system. You don't even have to worry about making sure your image's dimension are a multiple of the tile width and tile height for the system. Retro Graphics Toolkit can center images to conform to tile size. This makes it very easy to directly import an image. Also a selection of color quantization algorithms and ways to pick which tile uses what row allows for quick and easy high quality images. Retro Graphics Toolkit features an advanced sprite editor capable on creating groups making alignment much easier, even including buttons to do very easy alignment and Retro Graphics Toolkit can import an image creating a sprite group large images are divided up using as few sprites as possible. Another feature that goes in hand with Retro Graphics Toolkit's philosophy of easy importing is the sprite sheet importer. Typically sprite sheets have many sprites on it that are spaced in a non-uniform way with a background color that is not used anywhere on the sprite or uses an alpha channel. This means that simply dividing up the image into even rectangles will not work. Retro Graphics Toolkit solves this problem by first identifying the background color If a background color was used that is treated as transparent. Next line segments are created and those line segments are merged to create rectangles. The longest line segment determines the width and height of the rectangle that is created. The level editor is a new feature starting in version 0.8 RC1. Sprites from the sprite editor can be displayed on the level editor as well. The easy to use palette editor is great for viewing the entire palette at once making changes a breeze. Levels are constructed with chunks. This shows Green Hill zone's graphics converted to the NES. And it looks much better than Somari. This shows the power of Retro Graphics Toolkit. Source code: https://github.com/ComputerNerd/Retro-Graphics-Toolkit Windows binary: https://github.com/ComputerNerd/Retro-Graphics-Toolkit/blob/master/RetroGraphicsToolkit.exe.7z To download the windows binary click "View Raw" (without the quotes). If you have any bug reports, feature requests, pull requests or patches I would like to hear about them. With Lua scripting it should be much easier to get Retro Graphics Toolkit to do what you need as opposed to writing your own tool. If you made any useful Lua scripts be sure to post them.