A simple program to convert a Windows bitmap to an Adafruit GFX library bitmap array for monochrome OLED displays.

bmp2arduino.cs

/*
 * bmp2arduino.cs
 * Will Eccles 2019
 * 
 * Takes a Windows bitmap file and outputs a C header containing a bitmap array
 * to be used with the Adafruit GFX library. Only works for monochrome files at this time.
 * All pixels that are not black or transparent are assumed to be white.
 * 
 * Run with no arguments to see usage.
 * 
 */

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Text.RegularExpressions;

namespace bmp2arduino
{
	class bmp2arduino
	{
		static void E(int e) { Environment.Exit(e); }

		static void Usage()
		{
			Console.WriteLine("Usage: bmp2arduino <input.bmp> <output.h> <image_name_c>\n");
			Console.WriteLine("       input.bmp:\tA BMP file to convert.\n");
			Console.WriteLine("       output.h:\tA C header file to output to.\n");
			Console.WriteLine("       image_name_c:\t A valid C identifier for the image.");
		}

		static void Main(string[] args)
		{
			if (args.Length == 0)
			{
				Console.WriteLine("Please supply a bitmap file.");
				Usage();
				E(1);
			}

			if (args.Length == 1)
			{
				Console.WriteLine("Please supply an output file name.");
				Usage();
				E(1);
			}

			if (args.Length == 2)
			{
				Console.WriteLine("Please supply a C identifier for the image.");
				Usage();
				E(1);
			}

			string inbmp = args[0];
			string outh = args[1];
			string ident = args[2];

			if (!Regex.IsMatch(ident, @"[_A-Za-z][_A-Za-z0-9]*"))
			{
				Console.WriteLine($"\"{ident}\" is not a valid C identifier.");
				E(1);
			}

			Bitmap b = null;

			try
			{
				b = new Bitmap(inbmp);
			}
			catch
			{
				Console.WriteLine("Error opening bitmap! Invalid path or permissions.");
				E(1);
			}

			int hpadding = (8 - (b.Width % 8)) % 8;

			string imgarr = "";

			Color pixel;
			int bcounter = 0;
			for (int y = 0; y < b.Height; y++)
			{
				for (int x = 0; x < b.Width; x++)
				{
					if (bcounter == 0)
					{
						imgarr += 'B';
					}

					pixel = b.GetPixel(x, y);

					if ((pixel.R == 0 && pixel.G == 0 && pixel.B == 0) || pixel.A == 0)
					{
						imgarr += '0';
					}
					else
					{
						imgarr += '1';
					}

					if (bcounter == 7)
					{
						imgarr += ",";
					}

					bcounter++;
					bcounter %= 8; // reset bit counter if necessary
				}

				bcounter = 0;

				if (hpadding > 0)
				{
					imgarr += new string('0', hpadding);
					imgarr += ",";
				}

				imgarr += '\n';
			}

			string ident_upper = ident.ToUpper();

			string finaloutput =
				"/* Auto-generated with bmp2arduino: https://gist.github.com/WillEccles/240ff4850ea560aa617043eafd66e9f6 */\n\n" +
				$"#ifndef {ident_upper}_HEADER\n" +
				$"#define {ident_upper}_HEADER\n\n" +
				"#include <Arduino.h>\n\n" +
				$"// Width of {ident}\n" +
				$"#define {ident_upper}_WIDTH {b.Width + hpadding}\n" +
				$"// Height of {ident}\n" +
				$"#define {ident_upper}_HEIGHT {b.Height}\n" +
				$"// Horizontal padding for {ident}\n" +
				$"#define {ident_upper}_PADDING {hpadding}\n\n" +
				$"const uint8_t {ident}[] PROGMEM = {{\n" +
				imgarr +
				"};\n\n" +
				$"#endif /* {ident_upper}_HEADER */\n";

			try
			{
				System.IO.File.WriteAllText(outh, finaloutput);
			}
			catch
			{
				Console.WriteLine("Error writing to output file! Invalid path or permissions.");
				E(1);
			}
		}
	}
}