BMF – ByteMap font format
Version 1.1
| offset | size | meaning |
|---|---|---|
| 0 | 4 | magic header (0xE1E6D51A) |
| 4 | 1 | version (0x11 for v1.1) |
| 5 | 1 | line-height should be equal to or greater than size-under – size-over |
| 6 | 1 | size-over the base line (–128…127) measure from base line to top of capital letters, in pixels; should be negative |
| 7 | 1 | size-under the base line (–128…127) measure from base line to lowest extends (of letters like "y", "g"), in pixels; usually positive |
| 8 | 1 | add-space after each char (–128…127) how many pixels to add after plotting each character |
| 9 | 1 | size-inner (small letters height) (–128…127) measure from base line to top of small letters; should be negative |
| 10 | 1 | count of used colors |
| 11 | 1 | highest used color attribute |
| 12 | 4 | reserved |
| 16 | 1 | number of colors in palette (P) |
| 17 | P*3 | font palette (RGB, 0…63 per component) |
| 17+P*3 | 1 | title length (T) |
| 18+P*3 | T | title string |
| 19+P*3+T | 2 | number of characters in font i.e. having non-zero size or shift (N) |
| 20+P*3+T | ? | ’tablo‘ - character bitmap definitions |
| offset | size | meaning |
|---|---|---|
| 0 | 1 | which character |
| 1 | 1 | character width (W) |
| 2 | 1 | character height (H) |
| 3 | 1 | relx – X offset from cursor position (–128…127) |
| 4 | 1 | rely – Y offset from cursor position (–128…127) |
| 5 | 1 | horizontal cursor shift after drawing the character |
| 6 | W * H | character bitmap (uncompressed, 8 bits per pixel) |
Character with zero size (width and height) and zero shift is considered empty/unused and as such is not stored. In addition, zero is a valid size of bitmap; in that case definition of the next character follows right after.
Example
Let addspace = 1 for this example. The red arrow (being size-over) is cursor position during outputing each character in the text.
| F | j | : | Q | |
|---|---|---|---|---|
| width | 4 | 4 | 1 | 10 |
| height | 8 | 9 | 4 | 9 |
| relx | 0 | –2 | 1 | 0 |
| rely | 0 | 2 | 2 | 0 |
| shift | 4 | 2 | 3 | 8 |
Pseudocode for loading
file = fopen("font.bmf", "rb");
buffer = fread(file, 18);
if (substr(buffer, 0, 5) != "\xE1\xE6\xD5\x1A\x11") {
return false; // not a BMF version 1.1
}
lineHeight = buffer[5];
sizeOver = buffer[6];
sizeUnder = buffer[7];
addSpace = buffer[8];
sizeInner = buffer[9];
usedColors = buffer[10];
highestColor = buffer[11];
colors = buffer[16];
palette = fread(file, colors * 3);
for (i = 0; i < colors * 3; i++) {
palette[i] *= 4; // stretch 0..63 values to 0..255
}
buffer = fread(file, 1); // title length
title = fread(file, buffer);
numChars = fread(file, 1);
for (i = 0; i < numChars; i++) {
whichChar = fread(file, 1);
tablo[whichChar] = fread(file, 5);
if (bitmapSize = tablo[whichChar][0] * tablo[whichChar][1]) {
bitmaps[whichChar] = fread(file, bitmapSize);
}
}
fclose(file);