//-------------------------------------------------------------------
//	pcx8bpp.cpp
//
//	This program displays the photograph stored in a .pcx file
//	using the VGA hardware's color-lookup table in 8-bpp mode.  
//
//	  compile using:  $ g++ pcx8bpp.cpp int86.cpp -o pcx8bpp
//
//	programmer: ALLAN CRUSE
//	written on: 27 AUG 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf(), perror() 
#include <fcntl.h>	// for open() 
#include <stdlib.h>	// for exit() 
#include <unistd.h>	// for read()  
#include <sys/mman.h>	// for mmap()
#include <sys/io.h>	// for outb()
#include "int86.h"	// for init8086(), int86()
#include "pcx.h"	// for PCX_FILE_HEADER

#define VRAM_BASE	0xA0000000
#define DAC_PORT	0x03C8

typedef unsigned char PEL;
PEL *vram = (PEL*)VRAM_BASE;

int vesa_mode = 0x4101, hres = 640, vres = 480;
char devname[] = "/dev/vram";
char pcxname[] = "issxmas.pcx";
struct vm86plus_struct	vm;

int main( int argc, char **argv )
{
	// open the vram device file
	int	dd = open( devname, O_RDWR );
	if ( dd < 0 ) { perror( devname ); exit(1); }
	
	// map the display memory into user space
	int	size = hres * vres;
	int	prot = PROT_READ | PROT_WRITE;
	int	flag = MAP_FIXED | MAP_SHARED;
	void	*mm = (void*)VRAM_BASE;
	if ( mmap( mm, size, prot, flag, dd, 0 ) == MAP_FAILED )
		{ perror( "mmap" ); exit(1); }	

	// open the image file
	int	fd = open( pcxname, O_RDONLY );
	if ( fd < 0 ) { perror( pcxname ); exit(1); }

	// memory-map the .pcx file into user-space
	size = lseek( fd, 0, SEEK_END );
	prot = PROT_READ;
	flag = MAP_PRIVATE;
	mm = mmap( NULL, size, prot, flag, fd, 0 );
	if ( mm == MAP_FAILED ) { perror( "mmap" ); exit(1); }

	// setup structure-pointers and display the image's parameters
	PCX_FILE_HEADER	*pcx = (PCX_FILE_HEADER*)mm;
	unsigned char	*image = (unsigned char*)((int)mm + 128 );
	unsigned char	*table = (unsigned char*)((int)mm + size - 3*256 );
	int	wide = pcx->x2 - pcx->x1;
	int	high = pcx->y2 - pcx->y1;
	int	npixels = wide * high;
	int	bytes_per_scanline = pcx->bplin;
	printf( "\nimage file: \'%s\' (%d bytes) \n", pcxname, size );
	printf( "screen resolution: %d-by-%d \n", wide, high );
	printf( "color depth: %d-bpp \n", pcx->bitpx ); 
	getchar();

	// set the graphics display mode
	init8086();
	vm.regs.eax = 0x4F02;
	vm.regs.ebx = vesa_mode;
	int86( 0x10, vm );
	if ( vm.regs.eax != 0x004F ) 
		{ 
		fprintf( stderr, "cannot set vesa mode %04X\n", vesa_mode );
		exit(1); 
		}

	// draw a screen border
	PEL	color = 7;
	int	x = 0, y = 0;
	do { vram[ y*hres + x ] = color; ++x; } while ( x < hres-1 );
	do { vram[ y*hres + x ] = color; ++y; } while ( y < vres-1 );
	do { vram[ y*hres + x ] = color; --x; } while ( x >      0 );
	do { vram[ y*hres + x ] = color; --y; } while ( y >      0 );
	getchar();

	// draw the (uncompressed) image to display memory
	int	xstart = (hres - wide)/2;
	int	ystart = (vres - high)/2;
	int	src = 0, dst = 0; // source and dest'n counters
	while ( dst < npixels )
		{
		int	reps = 1; // repetitions count (default=1)
		PEL	datum = image[ src++ ];
		if ( ( datum & 0xC0 ) == 0xC0 )
			{
			reps = (datum & 0x3F);
			datum = image[ src++ ];
			}
		while ( reps-- > 0 )
			{
			y = ystart + (dst / bytes_per_scanline);
			x = xstart + (dst % bytes_per_scanline);
			vram[ y*hres + x ] = datum;
			++dst;
			}
		}
	getchar();

	// now reprogram the VGA Color-Lookup Registers
	for (int reg = 0; reg < 256; reg++)
		{
		outb( reg, DAC_PORT );
		outb( table[ 3*reg + 0 ]>>2, DAC_PORT+1 );
		outb( table[ 3*reg + 1 ]>>2, DAC_PORT+1 );
		outb( table[ 3*reg + 2 ]>>2, DAC_PORT+1 );
		}
	getchar();

	// ok, now reprogram the color-registers for GrayScale 
	for (int reg = 0; reg < 256; reg++)
		{
		int	r = 0, g = 0, b = 0;
		outb( reg, DAC_PORT-1 ); // select register to read
		r = inb( DAC_PORT+1 );	// read 'red' component
		g = inb( DAC_PORT+1 );	// read 'green' component
		b = inb( DAC_PORT+1 );	// read 'blue' component
		int	avg = (30*r + 59*g + 11*b)/100;
		outb( reg, DAC_PORT );   // select register to write
		outb( avg, DAC_PORT+1 ); // write 'red' component
		outb( avg, DAC_PORT+1 ); // write 'green' component
		outb( avg, DAC_PORT+1 ); // write 'blue' component
		}
	getchar();

	// reset textmode display
	vm.regs.eax = 0x4F02;
	vm.regs.ebx = 0x0003;
	int86( 0x10, vm );
	printf( "\n\n" );
}