embedded-game-programming/tools/src/font_processor.c

#include <assert.h>
#include <ctype.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


int main(int argc, char** argv)
{
	if (argc != 6)
	{
		fprintf(stderr, "Usage: %s <input image> <layout file> <output header> <glyph width> <glyph height>\n", argv[0]);

		return 1;
	}

	const char* inFilename = argv[1];
	const char* layoutFilename = argv[2];
	const char* outFilename = argv[3];
	const int glyphWidth = atoi(argv[4]);
	const int glyphHeight = atoi(argv[5]);


	int imageWidth;
	int imageHeight;
	uint8_t* imageBuffer;
	{
		FILE* inFile = fopen(inFilename, "rb");
		assert(inFile);

		#pragma pack(push,1)
		struct BmpHeader
		{
			char magic[2];
			uint32_t totalSize;
			uint32_t reserved;
			uint32_t offset;
			uint32_t headerSize;
			int32_t width;
			int32_t height;
			uint16_t planes;
			uint16_t depth;
			uint32_t compression;
			uint32_t imageSize;
			int32_t horizontalResolution;
			int32_t verticalResolution;
			uint32_t paletteColorCount;
			uint32_t importantColorcount;
		} bmpHeader;
		#pragma pack(pop)

		// Read the BMP header so we know where the image data is located
		fread(&bmpHeader, 1, sizeof(bmpHeader), inFile);
		assert(bmpHeader.magic[0] == 'B' && bmpHeader.magic[1] == 'M');
		assert(bmpHeader.depth == 8);
		assert(bmpHeader.headerSize == 40);

		// Go to location in file of image data
		fseek(inFile, bmpHeader.offset, SEEK_SET);

		// Read in the image data
		imageBuffer = malloc(bmpHeader.imageSize);
		assert(imageBuffer);
		fread(imageBuffer, 1, bmpHeader.imageSize, inFile);

		imageWidth = bmpHeader.width;
		imageHeight = bmpHeader.height;

		fclose(inFile);
	}


	char** glyphLayout = NULL;
	int layoutRows = 0;
	{
		FILE* layoutFile = fopen(layoutFilename, "r");
		assert(layoutFile);


		// Count the number of lines in the file
		while (!feof(layoutFile))
		{
			char c = fgetc(layoutFile);

			if (c == '\n')
			{
				++layoutRows;
			}
		}


		// Return file position indicator to start
		rewind(layoutFile);


		// Allocate enough memory for one string pointer per row
		glyphLayout = malloc(sizeof(*glyphLayout) * layoutRows);
		assert(glyphLayout);


		// Read the file into memory
		for (int rowIndex = 0; rowIndex < layoutRows; ++rowIndex)
		{
			char* line = NULL;
			size_t len = 0;

			getline(&line, &len, layoutFile);


			int newlinePosition = strlen(line) - 1;

			if (line[newlinePosition] == '\n')
			{
				line[newlinePosition] = '\0';
			}


			glyphLayout[rowIndex] = line;
		}

		fclose(layoutFile);
	}


	printf("Input: %s\n", inFilename);
	printf("Output: %s\n", outFilename);
	printf("Width: %d\n", imageWidth);
	printf("Height: %d\n", imageHeight);
	printf("Glyph: %dx%d\n\n", glyphWidth, glyphHeight);

	FILE* outFile = fopen(outFilename, "w");
	assert(outFile);


	// Generate the preamble
	{
		fprintf(outFile, "// AUTOMATICALLY GENERATED. DO NOT EDIT.\n");
		fprintf(outFile, "\n");
		fprintf(outFile, "#pragma once\n");
		fprintf(outFile, "\n");
		fprintf(outFile, "#include <assert.h>\n");
		fprintf(outFile, "#include <stdint.h>\n");
		fprintf(outFile, "\n");
		fprintf(outFile, "\n");
		fprintf(outFile, "static const int GLYPH_WIDTH = %d;\n", glyphWidth);
		fprintf(outFile, "static const int GLYPH_HEIGHT = %d;\n", glyphHeight);
		fprintf(outFile, "\n");
		fprintf(outFile, "\n");
	}


	// Generate the GetGlyphIndex function
	int glyphCount = 0;
	{
		fprintf(outFile, "int GetGlyphIndex(char c)\n");
		fprintf(outFile, "{\n");
		fprintf(outFile, "	switch (c)\n");
		fprintf(outFile, "	{\n");

		for (int row = 0; row < layoutRows; ++row)
		{
			int glyphsInRow = strlen(glyphLayout[row]);

			for (int glyph = 0; glyph < glyphsInRow; ++glyph)
			{
				char c = glyphLayout[row][glyph];

				fprintf(outFile, "		");

				if (isalpha(c))
				{
					fprintf(outFile, "case '%c': ", tolower(c));
				}

				fprintf(outFile, "case '%c': { return %d; break; }\n", c, glyphCount);

				++glyphCount;
			}
		}

		fprintf(outFile, "		default: { assert(NULL); break; }\n");
		fprintf(outFile, "	}\n");
		fprintf(outFile, "}\n\n");
	}


	// Generate the font map with the calculated glyph bytes
	{
		fprintf(outFile, "static const uint16_t glyphMap[%d][%d] =\n", glyphCount, glyphHeight);
		fprintf(outFile, "{\n");

		for (int y = 0; y < layoutRows; ++y)
		{
			int glyphsInRow = strlen(glyphLayout[y]);

			for (int x = 0; x < glyphsInRow; ++x)
			{
				char c = glyphLayout[y][x];

				fprintf(outFile, "	// %c\n", c);
				fprintf(outFile, "	{\n");
				fprintf(outFile, "	");

				int count = 0;

				for (int row = y * glyphHeight; row < (y + 1) * glyphHeight; ++row)
				{
					uint16_t val = 0;

					for (int col = x * glyphWidth; col < (x + 1) * glyphWidth; ++col)
					{
						// BMP is laid out bottom-to-top, but we want top-to-bottom (0-indexed)
						int y = imageHeight - row - 1;

						uint8_t pixel = imageBuffer[y * imageWidth + col];

						int bitPosition = 15 - (col % glyphWidth);
						val |= (pixel << bitPosition);
					}

					fprintf(outFile, "0x%04X,", val);
					++count;

					// Put a newline after four values to keep it orderly
					if ((count % 4) == 0)
					{
						fprintf(outFile, "\n");
						fprintf(outFile, "	");
						count = 0;
					}
				}

				fprintf(outFile, "},\n\n");
			}
		}

		fprintf(outFile, "};\n");
	}

	fclose(outFile);

	printf("DONE\n");

	return 0;
}