Instructions on how to convert bitmaps into NES graphics.

howto_bitmaps_to_NES

Pre-requisite
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- Install GIMP:  https://www.gimp.org/
- Download the Shiru's NES Screen Tooll:  https://shiru.untergrund.net/software.shtml 
- Download this 8-bit color palette: http://zanagb.deviantart.com/art/The-NES-GIMP-Pallete-V2-197049739
- Import the palette into GIMP (Windows->Dockable Dialogs->Palettes, then Right-Click and import)


1 - Open your image in GIMP, preferably a 128x128 one.
2 - Go to Image -> Mode -> Indexed. Select "Use custom palette" and click on the colors icon. Navigate to the NESPAL.gpl file you just imported.
3 - While still in the Indexed Color Conversion dialog box, make sure "Remove unused colors from colormap" is selected. Also, for Dithering, choose "Positioned". Then click the "Convert" button.
4 - Now go to Image -> Mode -> RGB. Scale and/or adjust the canvas size to 128x128 if you haven't done so already.
5 - Again, go to Image -> Mode -> Indexed. This time, select "Generate optimum palette" and set the maximum number of colors to 4. For the Color Dithering option, choose "None". Click the "Convert" button.
6 - Export your image in bitmap format. You are now finished with GIMP.
7 - Open the NES Screen Tool application. Navigate to Import -> Import As TileSet.