ILI9341 Font Packer v1.1

What does it do?

Using a combination of a Teensy microcontroller, and an SPI flash memory IC, you can display (almost) any font on an ILI9341-compatible LCD display, using a modified version of Paul Stoffregen's ILI9341 and SerialFlash libraries for the Teensy.

Tested with Python 3.5 on Linux Mint 18. Python 2.x will possibly baulk at all the byte and string twiddling, but that shouldn't be hard to fix for those with the inclination and a foot in the distant past. Other platforms should work out of the box, but pull requests are welcome for any necessary fixes for Windows or OS X.

Don't forget to check the license of any font you use. Use of this software grants you no rights in that regard.

Requirements

The requirements are modest:

freetype-py >= 1.0.2
bitstring >= 3.1.5
docopt >= 0.6.2
pyserial >= 3.2.1

FreeType is the obvious one, it is available for all major platforms, and the Python wrapper works well.

Because the font format is very tightly packed (and, I must say, very clever), bitstring is used to smush everything together.

docopt because it is one of the most Pythonic and beautiful packages out there, and by far the best for command line argument parsing.

If you want to upload directly to your Teensy, you'll need pyserial to run rawfile-uploader.py.

What's inside?

The main application is font_packer.py:

ILI9341 Font Packer v1.1

Converts TrueType fonts to a compact binary bitmap format for use with Paul Stoffregen's ILI9341 library for the Teensy.

Usage:
    font_packer.py --height=<pixels> [--range=<range-string>] [--packed|--code|--smoke] <font-file> [<output>]
    font_packer.py -h | --help
    font_packer.py --version

Options:
    -h --help                   Show this screen.
    --version                   Show version.
    --height=<pixels>           The maximum height of the glyphs.
    --range=<range-string>      A range of Unicode codepoints to generate glyphs for [default: 32-126].
    --packed                    Sends the packed binary bitmap font to output or stdout.
    --code                      Generates C structs to output or stdout.
    --smoke                     Smoke proof. Displays to output or stdout the bitmaps of each character as asterisks.
    output                      Output file name or stdout if not supplied.

It generates a bitmap font from a TrueType or OpenType font (or any other font supported by FreeType2)

--height The height of the font in pixels. This isn't necessarily the actual height of the final bitmap due to space for accents and so on; the bitmap you see on your screen will be smaller. But it is what FreeType2 uses, and it is comparable to using non-antialiased type with no hinting in GIMP.

--range The range, in Unicode codepoints, of the glyphs you want to produce. This can be a disjoint range, such as 32,33,65-90. Gaps in the range will be replaced by the first glyph (space in this example), or by the glyph specified in the --placeholder parameter. These gaps won't take up any space in the actual bitmap array, they will just be an entry in the index array that points to the first glyph. Characters outside the minimum and maximum of the range are just ignored by the ILI9341 font rendering functions.

--packed Flag to output the font as a Teensy ILI9341 font rendering compatible structure. This can be stored on a flash chip (or SD card) and loaded at runtime. This is the default.

--code Flag to output C code in the same format as the example fonts provided by the display library. This enables the font to be compiled directly into the executable.

--smoke Produces a "smoke proof" ASCII art of each glyph using asterisks and spaces, similar to the Unix banner command. Useful for checking which glyphs will get output, and their size in pixels.

output File name to direct the output to. If this is missing the output gets sent to stdout.

filename The file name of a FreeType2 recognised font format. Only TTFs and OTFs have been tested, but others should work as well.

Aside from this there is rawfile-uploader.py which is a modification of the same file found in the extras directory of the SerialFlash repository. This is used to upload a file to a flash chip attached to a Teensy (and probably Arduino-alikes as well), running the modified CopyFromSerial.ino sketch that can be found here.

How do I use it?

python font_packer.py --height=36 --range=43,45,46,48-57 --packed arial.ttf numbers.bin

Will output just the glyphs +-.0123456789 and replace , and / with a hollow rectangle.

Assuming the CopyFileFromSerial.ino sketch is running on the Teensy, you can upload the file like this:

python extras/rawfile-uploader.py /dev/ttyACM0 numbers.bin

If all goes well, the Teensy's LED will go out and stay off. If it flashes after upload, then there has been an error. The number of flashes indicate the error, which you can find in the code.

Compile and upload the examples/test.cpp file onto your Teensy, and you should see some black text on a yellow background.

A few things to note. Because you're loading the font into RAM, you need to malloc() enough space before loading it. Once loaded into memory, you need to fix up the two pointers that point to the index and the data. Also, the font rendering code expects a reference to a ILI9341_t3_font_t struct, so don't forget to dereference the pointer to your font you just allocated.

To do

The rendering library only supports 1-bit fonts. It would be good to provide at least 2-bit anti-aliased fonts.

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Copyright (c) 2016 GeoSpark

Portions of this code are released under the MIT License (MIT)

See the LICENSE file, or visit http://opensource.org/licenses/MIT