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Re: [ft] freetype on small embedded device

From: Stuart Longland
Subject: Re: [ft] freetype on small embedded device
Date: Thu, 30 Dec 2010 12:31:06 +1000
User-agent: Mutt/1.5.20 (2009-06-14)

Hi mpsuzuki,

On Thu, Dec 30, 2010 at 10:34:12AM +0900, address@hidden wrote:
> Hi,
> On Thu, 30 Dec 2010 11:06:55 +1000
> Stuart Longland <address@hidden> wrote:
> >This is a pet project I'm working, so I'm not working to a deadline.  I
> >have here three STM32F103-based development boards (72MHz ARM
> >Cortex-M3).  The microcontrollers themselves have 64kB RAM, 512kB flash,
> >and the boards incoroporate a 320x240 pixel LCD panel, capable of 18-bit
> >colour (6-bits/channel).  The device also has a 2GB MicroSD card
> >installed.
> Do you want to use FreeType2 on the system whose memory is 64kB?
> Or, 64kB is just only on-chip & additional memory is available?

64kB is the entire SRAM.  There is an external memory interface, to
which the LCD controller (Ilitek ILI9325; which has its own RAM) is

> I remember there had ever been several posts asking for the
> applicability of FreeType2 on extremely small systems (in comparison
> with Unix-like systems assuming MMU), but usually the engineers
> asking the question tell that the interpreter of TrueType is not
> essential for their purpose and what they wanted are bitmap loader,
> then, "FreeType2 is not the best solution for the people looking
> for bitmap loader" was the answer in most cases.

Indeed, it's a sledgehammer to crack a wallnut approach.  I'm also
interested to know if there's some similar project out there that would
be more suitable.

TrueType has the advantage that I can embed one small font file, and
scale it as necessary to draw all the text (and it'll be nice and
clear).  The disadvantage is the code requirement/processing overhead.

The thing I don't want to have to do is code a font handler for
variable-width fonts from scratch since converting the fonts over, and
writing code for kerning and such will be a major pain to get right.

TrueType implements these features already, but is a behemoth to cram
into a little device like this (perhaps I can strip out the unrequired
modules however).  There are likely other, better suited projects out
there, but my searches for them have proven fruitless thus far.  Hence
why I ask here. :-)

(And yes, I'm aware of some proprietary solutions; these boards came
with a uC-GUI demo on them, but what's the fun in that?)

> >The plan is to make a multi-function device that, amongst other things,
> >will hopefully be obtaining a GPS location and plotting that on a map.
> Hmm, so you want to establish SVG rasterizer on your system?

SVG again would be wonderful, but even primitive vector graphics would
be better than nothing.  I can draw simple polygons and lines[1] for
now, next will be curves and arcs, and that should be all that's
required.  Likely I'll synthesize curved sides by many straight sides,
then use the polygon routines to do the drawing.

Stuart Longland (aka Redhatter, VK4MSL)      .'''.
Gentoo Linux/MIPS Cobalt and Docs Developer  '.'` :
. . . . . . . . . . . . . . . . . . . . . .   .'.'             :.'

I haven't lost my mind...'s backed up on a tape somewhere.

1. Wikipedia provided the line-drawing algorithm, and I found a
public-domain polygon filling algorithm that, while it seems a little
buggy, seems to work well enough.

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