Bitmap Fonts

The format

Version 1.1 Version 1.2

Example #1

Example #2

For this example, let addSpace = 1, sizeOver = –8. The blue line is the base line, the blue cursor is the initial position to plot the text, the red cursor, being sizeOver pixels down from the base line, indicate cursor position before outputing each character of the text. Finally, to get to the actual top-left corners of each bitmap, we need to add the (relX, relY) vector from each character's tablo.

Working with the format

Pseudocode for loading a font

filename = "font.bmf";
file = fopen(filename, "rb");
buffer = fread(file, 17);
version = buffer[4];
if (substr(buffer, 0, 4) != "\xE1\xE6\xD5\x1A" || (version != 0x11 && version != 0x12)) {
  return false; // not a BMF, version 1.1 or 1.2
}
lineHeight = buffer[5];
sizeOver = buffer[6];
sizeUnder = buffer[7];
addSpace = buffer[8];
sizeInner = buffer[9];
usedColors = buffer[10];
highestColor = buffer[11];
alphaBits = buffer[12];
extraPalettes = buffer[13];
reserved = buffer[14];
numColors = buffer[16];
palette = fread(file, numColors * 3);
for (i = 1; i <= numColors * 3; i++) {
  palette[i] *= 4; // stretch 0..63 values to 0..255
}
titleLength = fread(file, 1);
title = fread(file, titleLength);
asciiChars = fread(file, 2);
for (i = 0; i < asciiChars; i++) {
  whichChar = fread(file, 1);
  tablo[whichChar] = fread(file, 5);
  if (bitmapSize = tablo[whichChar][0] * tablo[whichChar][1]) {
    bitmaps[whichChar] = fread(file, bitmapSize);
  }
}
if (version >= 0x12) { // next goes for version 1.2 only
  unicodeChars = fread(file, 4);
  for (i = 0; i < unicodeChars; i++) {
    whichChar = fread(file, 4);
    tablo[whichChar] = fread(file, 5);
    if (bitmapSize = tablo[whichChar][0] * tablo[whichChar][1]) {
      bitmaps[whichChar] = fread(file, bitmapSize);
    }
  }
  numKerningPairs = fread(file, 4);
  kerningPairs = [];
  for (i = 0; i < numKerningPairs; i++) {
    fread(file, buffer, 10);
    kerningPairs []= buffer;
  }
}
fclose(file);

Pseudocode for layout

text = "EXAMPLE ABC";
originalX = cursorX = 30;
cursorY = 20;
lineBreaksEnabled = true;
for (index = 0; index < strlen(text); index++) { // for each character..
  whichChar = ord(text[index]);
  if (lineBreaksEnabled && (whichChar == 13)) { // line break
    cursorY += font.lineHeight;
    cursorX = originalX;
    continue;
  }
  charWidth = font.tablo[whichChar][0];
  charHeight = font.tablo[whichChar][1];
  charRelX = font.tablo[whichChar][2];
  charRelY = font.tablo[whichChar][3];
  charShift = font.tablo[whichChar][4];
  charBitmap = font.tablo[whichChar][5];
  for (bitmapY = 0; bitmapY < charHeight; bitmapY++) { // for each bitmap row..
    for (bitmapX = 0; bitmapX < charWidth; bitmapX++) { // for each bitmap column..
      colorAttribute = charBitmap[bitmapY * charWidth + bitmapX];
      if (colorAttribute) { // leave color attribute 0 as transparent
        setPixel(
          cursorX + charRelX + bitmapX, // x
          cursorY + font.sizeOver + charRelY + bitmapY, // y
          font.palette[colorAttribute]
        );
      }
    }
  }
  cursorX += charShift + font.addSpace; // update cursor position
  if (version >= 0x12 && index < strlen(text) - 1) {
    cursorX += font.kerningPairs[whichChar, ord(text[index + 1])];
  }
}