TURBO C GRAPHICS INFORMATION
This file contains information about the Turbo C graphics that is
not contained in the Additions and Enhancements manual,Please
read this file in its entirety,referring to it when you encounter
problems not addressed in the Additions and Enhancements manual.
TABLE OF CONTENTS
1,Adding GRAPHICS.LIB to the Turbo C Libraries
2,Switching to Text Mode
3,Internal Graphics Driver Pointers
4,Graphics Examples on CGA or Hercules
5,IBM 8514 Support
6,Compaq III Portable
7,Loading Drivers and Fonts at Runtime
8,How to Compile BGIDEMO
1,ADDING GRAPHICS.LIB TO THE TURBO C LIBRARIES
When you use graphics in a Turbo C program you either have to
include graphics.lib on the command line (if using TCC:
"tcc foo.c graphics.lib") or create a project with your program
and graphics.lib in it (TC),To avoid doing this,you can add
the graphics library modules to the standard C*.LIB libraries
using tlib,This may be accomplished easily by one or more of
the following tlib commands (don't leave out the ".lib"
extension on graphics.lib):
tlib cs +graphics.lib (small model library)
tlib cc +graphics.lib (compact model library)
tlib cm +graphics.lib (medium model library)
tlib cl +graphics.lib (large model library)
tlib ch +graphics.lib (huge model library)
It is probably a good idea to add the graphics modules to all the
standard library files,but if you know you will be using only
some memory models with graphics programs,or you are short on
disk space,you might choose to change only some library files.
Your current directory must be the directory where you keep the C
libraries,or you must include complete paths in the tlib command
line(s),For example:
cd \turboc\lib
tlib cm +graphics.lib
or
tlib \turboc\lib\cm +\turboc\lib\graphics.lib
Note that tlib will rename the original C*.LIB library to C*.BAK;
you might want to delete this file,or keep it around for
reference.
2,SWITCHING TO TEXT MODE
There are two routines that will switch the screen to text mode:
"textmode" and "restorecrtmode","textmode" should only be used
when the screen is in the text mode (presumably to change to a
different text mode),"restorecrtmode" should only be used when
the screen is in graphics mode (to temporarily escape to text
mode),These are the only contexts where textmode and
restorecrtmode may be used.
3,INTERNAL GRAPHICS DRIVER POINTERS
There are several far function pointers that are used by the
graphics library to access the low-level graphics routines,These
pointers are set to point to the internal graphics drivers when
"initgraph" is called,Subsequent calls to the graphics routines
will then invoke these internal drivers by calls through the
function pointers,The pointers are not tested for validity (to
handle the case when a graphics routine might be called before
initgraph),as that would introduce a lot of extra code,and slow
down those graphics routines.
In the compact,medium,large,and huge models,these pointers
are,therefore,initialized to point to a routine that will
display an error message,and abort the program (via exit()),in
case a graphics routine is called before initgraph.
In the tiny model there is no way to initialize far pointers to
point to a routine in the code,Furthermore,the tiny model shares
the standard library with the small model,Therefore,the graphics
driver pointers cannot be initialized in the tiny and small
models,and programs that attempt to call a graphics routine
before calling initgraph will most likely crash the machine.
The following graphics routines may be called before initgraph (or
after closegraph),detectgraph,getmoderange,setgraphbufsize,
registerbgidriver and registerfarbgidriver,registerbgifont and
registerfarbgifont.
4,GRAPHICS EXAMPLES ON CGA OR HERCULES
Most of the graphics examples in the manual (addendum) will work
best with an EGA or VGA adapter,When run on a CGA or monochrome
adapter,they might not produce the expected results,Therefore,
when running on non-EGA/VGA hardware,use the value "1" (one) in
place of the symbolic color constants,and use the following code
as the example for the arc,circle,ellipse,getarccoords,
getaspectratio,and pieslice routines:
#include <graphics.h>
main()
{
int graphdriver = DETECT,graphmode;
struct arccoordstype arcinfo;
int xasp,yasp;
long xlong;
initgraph(&graphdriver,&graphmode,"");
/* draw a 90 degree arc with radius of 50 */
arc( 100,120,0,89,50 );
/* get the coordinates of the arc and connect ends */
getarccoords( & arcinfo );
line( arcinfo.xstart,arcinfo.ystart,arcinfo.xend,arcinfo.yend );
/* draw a circle */
circle( 100,120,80 );
/* draw an ellipse inside the circle */
ellipse( 100,120,0,359,80,20 );
/* draw and fill a pieslice */
setfillstyle( HATCH_FILL,1 );
pieslice( 200,50,0,134,49 );
setfillstyle( SLASH_FILL,1 );
pieslice( 200,50,135,225,49 );
setfillstyle( WIDEDOT_FILL,1 );
pieslice( 200,50,225,360,49 );
/* draw a "square" rectangle */
getaspectratio( & xasp,& yasp );
xlong = ( 50L * (long) yasp ) / (long) xasp;
rectangle( 0,0,(int) xlong,50 );
getch();
closegraph();
}
5,IBM 8514 SUPPORT
An additional driver has been included with the BGI graphics
library,This driver interfaces to the IBM-8514 graphics card.
This is a new,hi-res graphics card capable of resolutions up to
1024x768 pixels,and a color palette of 256 colors from a list of
256K colors,The driver file name is IBM8514.BGI.
The IBM 8514 graphics card CANNOT be properly autodetected (it will
be recognized as VGA by the autodetection logic),Therefore,to
use the IBM 8514 card,the graphdriver variable must be assigned
the value IBM8514 (which is defined in GRAPHICS.H) when initgraph
is called,Detectgraph,or DETECT with initgraph should not be
used with the IBM 8514 (unless the emulated VGA mode is desired).
The supported modes of the IBM-8514 card are IBM8514LO (640x480
pixels),and IBM8514HI (1024x768 pixels),Both mode constants are
defined in GRAPHICS.H.
The IBM-8514 uses three 6-bit values to define colors,There is a
6-bit Red,Green,and Blue component for each defined color,To
allow the user to define colors for the IBM-8514,a new routine
was added to the BGI library,The routine is prototyped in
GRAPHICS.H as follows:
void far setrgbpalette(int colornum,int red,int green,int blue);
The argument colornum defines the palette entry to be loaded.
colornum is an integer from 0-255 (decimal),The arguments red,
green,and blue define the component colors of the palette entry.
Only the lower byte of these values is used,and out of this byte,
only the 6 most significant bits are loaded in the palette.
The other palette manipulation routines of the graphics library
may not be used with the IBM-8514 driver (i.e.,setallpalette,
setpalette,getpalette).
For compatability with the balance of the IBM graphics adapters,
the BGI driver defines the first 16 palette entries of the
IBM-8514 to the default colors of the EGA/VGA,These values can be
used as is,or changed using the setrgbpalette routine.
The floodfill routine will not work with the IBM 8514 driver.
6,COMPAQ III PORTABLE
If you are using the Compaq III Portable,enter the following
command at the DOS prompt before trying to use the 400 line mode:
SET SEL=CGA
7,LOADING DRIVERS AND FONTS AT RUNTIME
In addition to linking in drivers and fonts (converted by BGIOBJ),
you may load the driver and/or font files directly into memory at
runtime,and then register them through the registerfarbgidriver
and/or registerfarbgifont routines,The following example illustrates
this techique:
/* example of loading a font file into memory */
#include <graphics.h>
#include <io.h>
#include <fcntl.h>
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <process.h>
#include <alloc.h>
void main()
{
void * gothic_fontp; /* points to the font buffer in memory */
int handle; /* file handle used for I/O */
unsigned fsize; /* size of file (and buffer) */
int errorcode;
int graphdriver;
int graphmode;
/* open font file */
handle = open("GOTH.CHR",O_RDONLY|O_BINARY);
if (handle == -1)
{
printf("unable to open font file 'GOTH.CHR'\n");
exit(1);
};
fsize = filelength(handle); /* find out size of the file */
gothic_fontp = malloc(fsize); /* allocate buffer */
if (gothic_fontp == NULL)
{
printf("unable to allocate memory for font file 'GOTH.CHR'\n");
exit(1);
};
/* read font into memory */
if (read(handle,gothic_fontp,fsize) != fsize)
{
printf("unable to read font file 'GOTH.CHR'\n");
exit(1);
};
close(handle); /* close font file */
/* register font */
if (registerfarbgifont(gothic_fontp) != GOTHIC_FONT)
{
printf("unable to register font file 'GOTH.CHR'\n");
exit(1);
};
/* detect and initialize graphix */
graphdriver = DETECT;
initgraph(&graphdriver,&graphmode,"..");
errorcode = graphresult();
if (errorcode != grOk)
{
printf("graphics error,%s\n",grapherrormsg(errorcode));
exit(1);
};
settextjustify(CENTER_TEXT,CENTER_TEXT);
settextstyle(GOTHIC_FONT,HORIZ_DIR,4);
outtextxy( getmaxx() / 2,getmaxy() / 2,"Borland Graphics Interface");
getch(); /* hit a key to terminate */
closegraph(); /* shut down graphics system */
}
8,HOW TO COMPILE BGIDEMO
With TC.EXE:
1,Run TC.EXE
2,In the Project pulldown menu specify the project name
"BGIDEMO.PRJ"
3,From the main menu select the Run option
With TCC.EXE:
Compile from DOS with the following command line:
TCC bgidemo graphics.lib
Note that BGIDEMO will not run in the tiny model because of that
model's memory limitations.
END
