NES Tools - PNG to CHR and TTF to PNG Converters

A collection of command-line utilities NES system development.

Overview

nes_tools provides two complementary tools for NES asset creation:

• png2chr: Converts PNG images to NES CHR (character) format
• ttf2png: Renders TrueType fonts to PNG grids compatible with NES tools

Tools

png2chr

Converts indexed-color PNG images into NES CHR (CHRacter) format, used for sprite and background tile data.

Features

• Converts 8x8 pixel tiles to NES 2-bitplane CHR format
• Supports palette-based PNG images
• Validates input dimensions (must be multiples of 8x8)
• Handles 2-bit color depth (4 colors per tile)
• Comprehensive error reporting

Usage

png2chr <input.png> <output.chr>

Requirements

• Input PNG Format:
  • Must be indexed color (palette-based)
  • Dimensions must be multiples of 8x8 pixels
  • Palette colors: 0-3 (2 bits per pixel)
  • Each 8x8 tile is converted to 16 bytes in CHR format

Example

png2chr tileset.png output.chr

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ttf2png

Renders characters from a TrueType font into a PNG grid, creating font bitmaps suitable for NES applications.

Features

• Renders individual characters from TTF fonts to a customizable PNG grid
• Supports configurable character dimensions
• Creates 8-bit indexed color PNG output
• Flexible grid layout (width × height)
• Handles various font files with proper glyph rendering

Usage

ttf2png -chars:<characters> -width:<cols> -height:<rows> [-char_width:<w>] [-char_height:<h>] <input.ttf> <output.png>

Arguments

Argument	Description	Default
-chars:<characters>	Characters to render (required)	-
-width:<cols>	Grid width (number of columns)	-
-height:<rows>	Grid height (number of rows)	-
-char_width:<w>	Character pixel width	8
-char_height:<h>	Character pixel height	8
<input.ttf>	Path to TrueType font file (required)	-
<output.png>	Path to output PNG file (required)	-

Output Format

• PNG Type: Indexed color, 8-bit
• Palette: 2-color (black and white)
• Grid Size: `width × height` characters
• Image Size: `(width × char_width) × (height × char_height)` pixels

Example

ttf2png -chars:ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 -width:8 -height:5 -char_width:8 -char_height:16 font.ttf font_output.png

This creates a 8×5 grid (40 characters) with 8×16 pixel characters, resulting in an 64×80 pixel PNG.

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Building

The project uses CMake for building. Ensure you have the required dependencies installed:

Dependencies

• libpng: PNG image manipulation
• FreeType2: Font rasterization (ttf2png only)
• C99 or later: Required for compilation

Build Instructions

mkdir build
cd build
cmake ..
make

Executables will be created in the `build/` directory.

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Workflow: Font to CHR

A typical workflow for creating NES fonts:

1. Render TTF to PNG:

   ttf2png -chars:ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 -width:8 -height:5 font.ttf font.png

2. Convert PNG to CHR:

   png2chr font.png font.chr

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Test Assets

The project includes sample fonts in `data_test/ttf2png/`:

• PressStart2P-Regular.ttf
• PixelifySans-Regular.ttf
• VT323-Regular.ttf
• PixeloidMono.ttf
• Ithaca-LVB75.ttf
• And more...

Sample PNG for testing png2chr is located in `data_test/png2chr/`.

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