Mail Archives: djgpp/1997/10/05/04:18:36
| From: | "Alex Barsamian" <bigalex AT worldnet DOT att DOT net>
|
| Newsgroups: | comp.os.msdos.djgpp
|
| Subject: | Yet another graphics problem...
|
| Date: | Sun, 5 Oct 1997 01:28:48 -0600
|
| Organization: | Biohazard Software
|
| Lines: | 342
|
| Message-ID: | <617g3k$ipr@bgtnsc03.worldnet.att.net>
|
| NNTP-Posting-Host: | 12.65.147.223
|
| To: | djgpp AT delorie DOT com
|
| DJ-Gateway: | from newsgroup comp.os.msdos.djgpp
|
I started out tonite porting my crusty mode 13h real mode graphics code out
to djgpp. I can init the graphics mode okay, even write to the screen
without too much trouble. Now for some reason when I began to implement the
double buffer routines into the new source file, I compile without any
trouble, but about 1/4 of the time, when I should be seeing a PCX image, I
see a blank screen (in graphics mode), and the rest of the time I get a
lovely page fault. The source code from tonite's work follows. It's just a
series of simple, non-portable (yet!) functions to muck around in graphics,
yet I am confounded as to why it is not working as it should. Any
suggestions? (besides getting Allegro, which I do have, and think is
wonderful, but I just want to write this code by myself for the most part,
for the experience benefit :-) I think we can all understand that, huh?)
Thanks in advance. Please email as well as post, I may not be able to read
the newsgroups for a bit and I'd hate to muck thru bluesnews to find the
responses :-) )
regards,
alex
djvbepcx.c follows (the source is also attached in case the horribleness
that is IE4 screws up the formatting):
#include <stdio.h>
#include <stdlib.h>
#include <dpmi.h>
#include <sys/nearptr.h>
int c, width, height, bytes_per_line, i;
char ch;
unsigned char *videoptr = (unsigned char *)0xA0000;
unsigned char pallete[768];
unsigned char *buffer;
// switch vesa banks using int10
void VBE_SwitchBank(short bank) {
__asm__ __volatile__("
movw $0x4F05, %%ax;
xorw %%bx, %%bx;
int $0x10"
: : "d" (bank) : "ax", "bx", "dx"
);
}
// set a vbe mode
void VBE_SetMode(unsigned short mode) {
__dpmi_regs regs;
regs.x.ax = 0x4F02;
regs.x.bx = mode;
__dpmi_int(0x10, ®s);
}
// goto textmode
void VBE_Shutdown() {
VBE_SetMode(0x0003); // set to text mode
}
// Blit a buffer (unsigned char *) onscreen, switching
// banks no more than absolutely neccesary.
// this assumes the vbe 1.2 are present and functioning correctly, that is
// to say, all banks look like they are 64k whether they physically are or
// not
void copy_buffer()
char *source;
char *dest;
source=buffer;
dest = videoptr + __djgpp_conventional_base;
__djgpp_nearptr_enable();
/* 640*480*8bpp = 307200 bytes = 4*64K + 45056 bytes */
VBE_SwitchBank(0); // start at bank 0
memcpy(dest, source, 65536L); // copy 64k
VBE_SwitchBank(1); // switch to bank 1
source += 65536L; // copy 64k
memcpy(dest, source, 65536L); // rinse, lather, repeat . . . .
VBE_SwitchBank(2);
source += 65536L;
memcpy(dest, source, 65536L);
VBE_SwitchBank(3);
source += 65536L;
memcpy(dest, source, 65536L);
VBE_SwitchBank(4);
source += 65536L;
memcpy(dest, source, 45056L); // only 45056 because
640*480!=65536*5
__djgpp_nearptr_disable();
}
// get a pcx, skipping most unnecessary stuff that can be assumed
// e.g., size (for now 640x480 pcx's are all i'll use, 8 bpp, etc.
// I know this is far from portable but this is just to get this thing
// rolling
unsigned char *load_pcx(char *filename)
{
FILE *f; // file handle
int count, c; // loop vars
unsigned char data; // current data
int num_bytes; // number of bytes in RLE run
unsigned char *b; // buffer
f = fopen(filename, "r");
if (!f) {
printf("file not found\n");
return NULL;
}
getc(f); /* skip manufacturer ID */
getc(f); /* skip version flag */
getc(f); /* skip encoding flag */
getc(f);
width = -(getw(f)); /* xmin */
height = -(getw(f)); /* ymin */
width += getw(f) + 1; /* xmax */
height += getw(f) + 1; /* ymax */
b = malloc(width*height); // malloc an appropriate buffer
getc(f); /* skip DPI values */
for (c=0; c<16; c++) { /* skip the 16 color pallete */
getc(f); /* originally intended on using it
*/
getc(f); /* (for some reason . . . ) */
getc(f); /* which is why it looks like this
*/
}
getc(f); // skip junk
getc(f);
bytes_per_line = getw(f); // just in case i start to use double-
// scripted buffers
for (c=0; c<60; c++) /* skip some more junk */
getc(f);
count=0;
while(count<=(width*height)) {
// grab first piece of RLE data
data=getc(f);
// is it RLE?
if((data>=192) && (data<=255)) {
// if it is, how long is the run?
num_bytes=data-192;
// now that we know how long it is, grab the data
// for the actual run.
data=getc(f);
// plug (data) into the buffer (num_bytes) times
while(num_bytes-->0)
b[count++]=data;
} // end if RLE
// not RLE?
else
// plug it in to the buffer
b[count++]=data;
}
while (!feof(f)) { /* look for a 256 color pallete */
if (getc(f)==12) {
for (c=0; c<256; c++) {
pallete[c] = getc(f) / 4; // load it in
pallete[c*2] = getc(f) / 4;
pallete[c*3] = getc(f) / 4;
}
break;
}
}
fclose(f);
return b;
}
void VBE_Pal(unsigned char ColorNo, unsigned char R,
unsigned char G, unsigned char B) {
outp (0x03C8,ColorNo); // here is the pallette color I want to set
outp (0x03C9,R); // set r,
outp (0x03C9,G); // g,
outp (0x03C9,B); // and b compo appropriately
}
void main()
VBE_SetMode(0x101); // fire up graphics to 0x101
buffer=load_pcx("picture.pcx");
if(*buffer==NULL) { // do we have our picture?
VBE_Shutdown();
printf("error loading pcx");
exit(0);
}
for(i=0; i<256; ++i) // set the pallete appropriately
VBE_Pal(i, pallete[i], pallete[i*2], pallete[i*3]);
copy_buffer(); // put the buffer onscreen
getch();
VBE_Shutdown();
}
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