Fonts used by the game

The Following fonts are used by the game and can be used with the "Font()" class:

Font Name	Ingame Name/s	Ingame Example	Ingame Usage	Link to font
Droid Sans	droid	Example Droid	(Not used ingame)	Droid Sans
PF Tempesta Seven (Condensed)	pftempestasevencondensed	Example PF Tempesta Seven	HUD Elements like coin/key counters	PF Tempesta Seven
Team Meat Font	teammeatfont10 teammeatfont12 teammeatfont16 teammeatfont16bold	Example teammeatfont10 Example teammeatfont12 Example teammeatfont16 Example teammeatfont16bold	Main Menu Elements \| Pop-Ups Timer / Score Elements	Team Meat Font without Bold
Terminus	terminus terminus8	Example Terminus Example Terminus8	Debug Console / Isaac.RenderText()	Terminus
Upheaval	upheaval	Example Upheaval	Streak text	Upheaval
mplus (Japanese)	mplus_10r mplus_12b	Example mplus_10r Example mplus_12b	Replacement for all fonts aboth for Japanese translation. 10r is pf "Tempesta seven" / "Team Meat" replacement 12b is "Upheaval" replacement	PixelMplus (M+ Fonts)
kr Font (Korean)	kr_font12 kr_font14	Example kr_font12 Example kr_font14	TBD	No source found right now
Team Meat Font (Korean)	kr_meatfont14	Example kr_meatfont14	TBD	- Not available -

Basics of rendering a text

First we need to have a look at the basic process of writing on the screen. here is a sample code:

local testmod= RegisterMod( "testmod" ,1 );

local function onRender(t)
    Isaac.RenderText("Sample text", 50, 30, 1, 1, 1, 255)
end

testmod:AddCallback(ModCallbacks.MC_POST_RENDER, onRender)

Result:

The game uses the font-file "terminus.fnt" in order to render and display this text. this cant be changed. Luckily for us, this file contains "sprites" for all normal ASCII characters that exist out there (256 to be precise).

Rendering text with a different font

We can render any kind of text with a different font as well. This can be done by using the "Font()" class and its functions.

local f = Font() -- init font object
f:Load("font/droid.fnt") -- load a font into the font object
f:DrawString("droid",60,50,KColor(1,1,1,1,0,0,0),0,true) -- render string with loaded font on position 60x50y

All possible Fonts that can be drawn:

Render Special Characters

The game allows us to write anything into the "displayed text" argument that is part of the ASCII standard for characters. For characters a-z, 0-9 and ,.#+;:_'*~° this works without any problems and without using any kind of "hack". Now if we just strait up try to type in ' ä ' or ' ß ' to let it render as text, it will not look as intended.

In order to fix this problem we have to use the "raw" version of said characters. Example:

\197

prints:

Ä

So in order to print special characters, just replace them in the code like this:

Isaac.RenderText("S\228mple text", 50, 30, 1, 1, 1, 255)

prints:

Sämple text

List of all supported characters and their counterpart

Creating .fnt files

The Developer _Kilburn mentioned that fonts can be created using this Tool: https://www.angelcode.com/products/bmfont.

The best results can be made by converting Bitmap fonts, since they allow for smaller fontsizes.

Font Settings:

Font - choose a font thats very readable in small sizes (~8-10px height)
Charset - Unicode
Size - the general size of the characters in pixels. normal values are between 10 and 16
Height - can be used to squish/strech the
Match char height - the charactersize will be choosen based on the character, and not the size defined in Size
Bold / Italic - What font styling should be used
Output invalid char glyph - Characters that dont have a sprite will be put on the spritesheet, too. This can create holes in the spritesheet
Do not include kerning pairs - ?
Rasterization - used to smooth the font sprites. Not recommended for Isaac since we want pixel-perfect fonts!
Outline thickness - Define if an outline should be drawn around the character. In Isaac, this is always ~1px

Export Options:

Padding - Padding around each character, in pixels
Spacing - Space between characters, in pixels
Equalize the cell heights - will align all characters in a way, so they take up the least space vertically. off = they group in more uniform rows
Width / Height - Width and Height of each character spritesheet. If spritesheet isnt big enough, multiple files will be created
Bit depth - how many Bits should be used per color. ALWAYS choose 32 bit!
Pack chars in multiple Channels - Dont use this. We need all channels for out font because of transparencies!
File format - Choose Binary to create ".fnt" files
Textures - always set it to "png"
Compression - (only one option available)