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FZX: a new standard format and driver for proportional fonts
FZX is a very compact and efficient (although extremely flexible and powerful) standard format to create new fonts for the ZX-Spectrum. It supports proportional fonts, you can print characters anywhere on screen, and it's very easy to use in Sinclair BASIC, or called directly from Assembly routines.
The official FZX font format definition (including several sample fonts) is now available in FZX_Standard.zip, a tape file containing some practical examples is available in FZX.tap.zip, and the source code for the proportional printing driver is available in FZX_Driver.zip
However let's skip all the tech details and go straight to the interesting stuff! Every character in a regular ZX-Spectrum font is designed using a 8x8 grid like this:
But using FZX, each character definition is fully configurable and uses an arbitrary sized grid, like this:
In the example above, the character pixels are defined in a smaller 5x5 grid, and everything else is configurable. This particular FZX font specifies that all characters are 9 pixels tall ("height"), character "a" is located at a distance of 2 pixels from the top ("shift"), character "a" is 5 pixels wide ("width"), and there should be 2 pixels of distance before the next character ("tracking").
All these configurations make it possible to define proportional fonts that are fully flexible and configurable, but still very compact, using about the same amount of memory as a regular font.
Now let's consider a practical example. This is the original Sinclair font:
And here's the same text, using the same font style, but now converted to take advantage of FZX format using proportional spacing:
Although it's the same font style and size, the latter version is more comfortable to read and doesn't take so much room on screen, so it's certainly an improvement!
Another nice feature of FZX format is that it supports quite large fonts, with characters up to 16 pixels wide. Here's another example, this time using a much larger font called "Grotesk" (also supplied in the link above):
So how do you use FZX fonts in practice? It's actually very simple. First, load the driver from tape (together with any FZX font of your choice) and initialize it only once, like this:
Afterwards, simply use PRINT #4 to print your text, for instance:
Using font "Zaibatsu" for instance (also supplied in this package), the program above will produce the following result:
That's easy, right? :)
As indicated in the screen above, Andrew Owen and I have worked together to create FZX. He concentrated on defining the standard (with some assistance from Paul van der Laan) and designing the sample fonts supplied in this package, while I focused on coding it. Anyway everything presented here is open source and royalty-free, so you are welcome to use any of this material in your own programs (even commercial releases) and to create new FZX fonts yourself!
The official FZX font format definition (including several sample fonts) is now available in FZX_Standard.zip, a tape file containing some practical examples is available in FZX.tap.zip, and the source code for the proportional printing driver is available in FZX_Driver.zip
However let's skip all the tech details and go straight to the interesting stuff! Every character in a regular ZX-Spectrum font is designed using a 8x8 grid like this:
But using FZX, each character definition is fully configurable and uses an arbitrary sized grid, like this:
In the example above, the character pixels are defined in a smaller 5x5 grid, and everything else is configurable. This particular FZX font specifies that all characters are 9 pixels tall ("height"), character "a" is located at a distance of 2 pixels from the top ("shift"), character "a" is 5 pixels wide ("width"), and there should be 2 pixels of distance before the next character ("tracking").
All these configurations make it possible to define proportional fonts that are fully flexible and configurable, but still very compact, using about the same amount of memory as a regular font.
Now let's consider a practical example. This is the original Sinclair font:
And here's the same text, using the same font style, but now converted to take advantage of FZX format using proportional spacing:
Although it's the same font style and size, the latter version is more comfortable to read and doesn't take so much room on screen, so it's certainly an improvement!
Another nice feature of FZX format is that it supports quite large fonts, with characters up to 16 pixels wide. Here's another example, this time using a much larger font called "Grotesk" (also supplied in the link above):
So how do you use FZX fonts in practice? It's actually very simple. First, load the driver from tape (together with any FZX font of your choice) and initialize it only once, like this:
CLEAR 59999: LOAD "Sinclair"CODE 60000: LOAD "FZXdriver"CODE 65000: RANDOMIZE USR 65000
Afterwards, simply use PRINT #4 to print your text, for instance:
PRINT #4;AT 0,0;"FZX driver code (c) Einar Saukas"'"FZX font format (c) Andrew Owen" PRINT #4: FOR f=32 TO 127: PRINT #4;CHR$ f;: NEXT f
Using font "Zaibatsu" for instance (also supplied in this package), the program above will produce the following result:
That's easy, right? :)
As indicated in the screen above, Andrew Owen and I have worked together to create FZX. He concentrated on defining the standard (with some assistance from Paul van der Laan) and designing the sample fonts supplied in this package, while I focused on coding it. Anyway everything presented here is open source and royalty-free, so you are welcome to use any of this material in your own programs (even commercial releases) and to create new FZX fonts yourself!
Post edited by Einar Saukas on
Creator of ZXDB, BIFROST/NIRVANA, ZX7/RCS, etc. I don't frequent this forum anymore, please look for me elsewhere.
Thanked by 1farvardin
Comments
Great work Chaps.
Paddy
IIRC my effort used 2 bytes for height, width and then the character itself. I'm guessing FZX works on a similar principal?
One thing that needs correction in the example above however, is some of the terminology.
• What is called “baseline” should actually be called “body height”. In Latin typography the baseline is the imaginary line where most uppercase and lowercase letters are standing on.
• “Leading” is also not the correct word to describe the situation above. I would rather use the word “vertical offset”. The term “leading”, also sometimes referred to as “line spacing”, is the distance between two lines of text, measured from baseline to baseline.
Also see this Wikipedia article. :)
Looks great and the FZX is a very nice initiative. Kudos to you and Andrew on this!
One question I have is whether the spacing (space) width is configurable?
Bytes:Chuntey - Spectrum tech blog.
Any reason why you need both "leading" and "baseline"? Given you know height already, I would assume knowing offset above baseline is enough. At least that always sufficed for me...
And AFAIK, your "tracking" is often referred to as "kerning". Just nitpicking... :)
Patrik
I am afraid that is not correct. They are two different things related to the horizontal spacing of characters. I’ll try to explain it as good as I can, although this is a bit specialist.
First of all, in traditional typefaces letters always have a certain width that already includes some whitespace on the left and on the right of the black shape. These are called the left and right “sidebearings” or “margins”. This makes sure that when different letters are placed next to each other they have a certain distance, and don't clash.
The designer of a typeface may find that certain combinations of two letters are too close, or too far apart. So in that case he can make an exception to the default spacing for that particular letter combination, and create a “kerning pair”. That is kerning.
The user of a typeface may find that the normal spacing (including kerning) of a typeface looks too tight, or too wide. In that case many software allows users to give more spacing to the text overall, and that is called “tracking”.
As far as I understood from Andrew when he wrote about the FZX format, spacing can be defined in two different ways (but correct me if I’m wrong). It is possible to define with one value how many pixels will be put between all letters all the time. So in this case only black shapes are defined for the font, and the spacing is done automatically. This could be called “tracking”, more or less.
On the other hand it is also possible to define an advance width for every character individually. This will make the font data bigger, but gives the font designer the possibility to customise the spacing of every character.
All tech details are available in file FZX_Standard.zip, this is the reason I didn't bother to put them in this post. The package also contains file "Sinclair.fzx.asm" with the source code of this font, so it can be used as an example (and template) to create others.
The FZX format has 3 parts:
This way, there's no need to waste room in the character grid with the empty space above, below, and after each character, thus making this format very flexible and compact. :)
Ops, Andrew told me but I forgot to mention your help in the original post. :(
Sorry, I have just edited it to add this information now!
Thanks!
OK, I will fix this terminology in the next update.
Is there another term instead of vertical offset? The term offset also applies to the difference between 2 addresses in memory, which is part of the FZX format, thus also using offset for another purpose would be confusing...
Thanks!
All 4 parameters in this figure are configurable:
Actually the FZX format also supports "kern" (not shown in figure above), which basically "moves" an specific character a few pixels to the left, printing it closer to the previous character. Take a look at this example:
The example above shows font "Sinclair" that uses 2 pixels of distance (tracking) between characters. However if you look carefully, you should notice that letter semi-colon and letter "j" are only 1 pixel away from previous character. Both these characters are defined with "kern=1".
The printing routine uses hires coordinates, so you can print anywhere on screen. For instance:
In example above, y is the vertical coordinate (pixel line from 0 to 191) and x is the horizontal coordinate (pixel column from 0 to 255).
The [strike]"baseline"[/strike] "height" is defined just once for the entire font. Each character only specifies its [strike]"leading"[/strike] "shift".
We have both "tracking" and "kern", but they have different meanings. "Tracking" is the regular distance between every 2 characters, defined only once for the entire font. "Kern" is a smaller adjust in distance, specified for certain characters only.
For instance, font "Sinclair" has "tracking=2", but characters "j" and semi-colon have "kern=1". Technically the alternative would be using "tracking=1" for this font and use additional empty spaces on the left of every character except "j" and semi-colon, but this would give users more work, spend more bytes in certain fonts, and do not allow printing most characters at pixel column zero. So there are some advantages in making this distinction...
Exactly!
No, this is not correct. The second alternative is "kern", which is a small adjust (3 pixels at most) in distance, as described in my previous post. In practice, it works as if the specified "kern" value was subtracted from "tracking" when calculating distance from previous character.
Fortunately using "kern" doesn't make the font data any bigger, although this is the reason "kern" is limited to 3 pixels maximum.
Right. However "kerning pairs" are not very viable in 8 bit computers because they would make the font a lot larger, and the printing routine a lot slower. This is the reason FZX only provides a simplified version of "kern" for single characters, as described above.
Thanks!
Only if you configure your emulator to restart the tape automatically from the beginning...
I could add some checking to prevent this, but I prefer to keep the demo as simple as possible, so people can easily understand the listing. Thanks for the notice anyway!
Thanks, I will fix this definition in the next update!
Perfect!
You realise you've basically deprecated all my text driver stuff for Boriel's ZX Basic now, don't you? :P
Ah well. Clearly we need to get this into the ZX Basic library wiki next.
(And I had this idea bouncing around in my head for a text based game, too. And this is /perfect/ for it, I think. Awesome timing.)
I do like this font driver and its usage. It's soooo amazing! :-)
If I had this routine in the 80s. We would have done an E-Book reader in the early 80s... ;-)
But seriously: Small code, amazing abilities and easy to use. For me, nothing can be done better... Thanks to these creative programmers!
There are no problems, only solutions (K. Flynn)
Visit my ZX-Modules homepage with lot of free programs!
Or visit my music-related website if you're interested in synthesizer music or computer animations and movies I've created
Thanks!
Now we only need a good FZX editor. Any chance we could convince someone with a special talent for creating graphical editing tools, such as the author of ZX-Paintbrush? :)
Sorry, I skimmed over that...
Well, I have quite a bit of history with typesetting, so don't worry.
Right, these are assumed to be 0 here.
Not exactly. The (extra) horizontal spacing between two glyphs is called kerning. If you increase it or decrease it (between neighboring glyphs), you refer to it as adjusting the kerning. So you are right about the kerning pair, but that is just specifying an exception for the otherwise default kerning of a glyph (which may or may not be zero).
Indeed, but that it is not an attribute of a glyph at all, so it's unlikely what the OP had in mind in his image.
Right. So what was the problem?
EDIT: Ah, reading the later messages reveals what he meant. Perhaps it might be better to have a figure which shows few more letters printed and which illustrates which are per glyph parameters and which are not.
Patrik
The routine already implements proper error handling, so it will never crash if a program tries to use it incorrectly. For instance, if the user tries to print something outside the screen, it will give you error "5 Out of screen".
However it always assume the provided FZX font is valid, because checking font consistency every time a character is printed would make the routine extremely slow. Remember that the ZX-Spectrum is just a 8 bits machine, so we need to make some sacrifices to achieve good speed. Besides, how many machine code routines do you know for the Spectrum, that won't crash if you don't load it correctly in memory?
Current driver version already supports loading several fonts in memory at the same time, then switching between them using a pair of POKEs. This is described in the documentation.
We are also planning to release another "enhanced" version of the FZX driver (slightly bigger but more powerful), that will provide an easier way to switch between multiple fonts. Both versions of the driver will be available, so you can choose which one you want.
FZX is an open standard. If other people wants to create additional tools such as this converter, they are welcome!
Would you be interested to implement this converter yourself? :)
Exactly! The example you mentioned defines a 1 pixel "kern" for semi-colon.
Thanks for the suggestion!
I plan to post later a proper tutorial that should help clarify these issues, although I won't have time this week unfortunately...
Any of them would be fine. Personally I suggest BDF because it seems to be simpler, well documented, and quite popular. A conversor from BDF to FZX would be great...
Ah.. I was actually referring to the SPACE (blank) character (Chr$ 32) which in Sinclair font is 8-pixels wide. But am I correct in thinking that if we specify kerning and leading for this character as well, we can reduce the spacing left between words?
Bytes:Chuntey - Spectrum tech blog.
Patrik
The width of character SPACE is configurable, so it's easier to change it directly.
For instance, font "Sinclair" defines width=6 for character SPACE:
Since "Sinclair" defines tracking=2 (which is a configuration that applies to the entire font), it means current spacing between words is:
previous letter tracking + SPACE width + SPACE tracking = 2+6+2 = 10
If you reduce the width of character SPACE to 1, the spacing between words will be:
previous letter tracking + SPACE width + SPACE tracking = 2+1+2 = 5
Now if you want an even smaller spacing between words, you can also add "kern" to character SPACE. If you use kern=3, it will be:
previous letter tracking - SPACE kern + SPACE width + SPACE tracking = 2-3+1+2 = 2
However that would be too small :)
Bytes:Chuntey - Spectrum tech blog.
These fonts look great!
However the manual mentions lots of proportional fonts and at least 1 large font, but I could only find 4 regular sized fonts inside this program (using EXT-1 to EXT-4, or EXT-I). Where can I find the others?