Programming tools for the X16
The object files are bundled into several libraries, and the header files are copied into /include.
A handy method for changing the character "ROM" image in VERA.
- Burtle's PRNG (two versions) (burtle2.h)
- A cheap square-root function (math.h)
- A cheap byte-sized TRIG table (img/TRIG)
A PSG library with some primitive ADSR functionality.
A library for creating and moving sprites around.
This is a minimal library for pausing for 1 to 255 jiffies, and for getting the millisecond count from tv_nsec.
This is similar to a Z-text decoder. It can decode from RAM or from a buffer.
main.c demonstrates the use of sprite.h and sprite.c for defining and placing sprites.
The SpriteDefinition data structure is the payload used to communicate sprite attributes to the functions. There are some things to be aware of:
uint16_t block;
This is expected to be the actual mid- and low-memory address in VERA; for example, 0x4000 is typically the right place to start loading sprite data, so .block = 0x4000 would point to the beginning of sprite data.
uint8_t mode;
uint8_t layer;
uint8_t dimensions;
Familiarize yourself with the #defined constants for these fields.
int x : 15;
int y : 15;
These fields are large on purpose: to allow incremental movement. Please refer to the two macros for scaling screen locations to these fields: SPRITE_X_SCALE() and SPRITE_Y_SCALE().
There are also two tools for creating sprite files in the /sprite folder:
png2sprite.py is copied from x16-demo, and converts a PNG image to a C style array. c2bin.pl is even more useful: it converts a PNG image to a directly loadable binary.
Pixobject files were used in the 1990s in certain applications. They were simple, ascii-encoded graphic images with a line of metadata.
Pixobjects are limited, but useful in that they are easy to edit.
The /sprite/pixobject folder contains two utilities: pix2bin.pl, which converts a pixobject to a directly loadable binary sprite file, and bin2pix.pl, which takes a sprite binary file and creates a pixobject from it.
The pixobject file format is an elementary raster image storage format. It consists of:
1. A header line, containing the object's name, its bits per pixel, and its dimensions.
2. Data lines following. Hexadecimal digits are interpreted properly.
Values from 0 up to 61 are handled as 0-9, A-Z, and a-z.
The "*" character represents a simple "on" or white value.
The " " character represents a simple "off" or black value.
A full 8 bit range of values are not handled.
Example:
house1 4bpp 16x8
******
**********
**************
**********
*** ** ***
****** ***