#include <stdio.h>
#include <X11/Xos.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

#define WIDTH	320
#define HEIGHT	240

#define RSIZE	4
#define GSIZE	4
#define BSIZE	4

Display *dpy;
int scr;
Window win;
GC gc;
XColor defs[RSIZE][GSIZE][BSIZE];
XImage *image, *image2;
int use_truecolor=0;
int nshift_red, nshift_green, nshift_blue;

static int getshiftbit(unsigned long mask) {
    int i, n;
    for (i=0; i<sizeof(mask)*8; i++) {
        if (mask & 1) {
            if (mask == 0xff) return(i);
            else return(-1);
        }
        mask >>= 1;
    }
    return(-1);
}

int check24() {
  if (DefaultDepth(dpy,scr) == 24) {
        XVisualInfo xvit, *xvi;
        int n, i;
        xvit.depth = 24;
        xvit.class = TrueColor;
        xvi = XGetVisualInfo(dpy,VisualDepthMask|VisualClassMask,&xvit,&n);
        if (xvi) {
            for (i=0; i<n; i++) {
                nshift_red = getshiftbit(xvi->red_mask);
                nshift_green = getshiftbit(xvi->green_mask);
                nshift_blue = getshiftbit(xvi->blue_mask);
                if (nshift_red >= 0 && nshift_green >= 0
                    && nshift_blue >= 0) {
                    use_truecolor=1;
		    return(1);
                }
                xvi++;
            }
        }
    }
    return(0);
}

XImage *init_ximage(int w,int h) {
    int format, bitmap_pad, depth;
    XImage *image;
    depth = DefaultDepth(dpy,scr);
    if (depth == 1) {
	format = XYPixmap; bitmap_pad = 32;
    } else if (depth == 8){
	format = ZPixmap; bitmap_pad = 8;
    } else if (depth == 16){
	format = ZPixmap; bitmap_pad = 16;
    } else if (depth==24) {
	format = ZPixmap; bitmap_pad = 32;
    } else {
	fprintf(stderr,"unsupported depth %d\n",depth);
	exit(-1);
    }
    image = XCreateImage(dpy,DefaultVisual(dpy,scr),depth,format,0,0,
			 w,h,bitmap_pad,0);
    if (image == 0) {
	fprintf(stderr,"XImage structure allocation failure\n");
	exit(-1);
    }
    if ((image->data =(char *) malloc(image->bytes_per_line * h)) == NULL) {
	fprintf(stderr,"image memory allocation failure\n");
	exit(-1);
    }
    return(image);
}

void init_cmap() {
    Colormap cmap;
    int i,j,k;

    check24();
    if (use_truecolor) return;
    cmap=DefaultColormap(dpy,scr);
    for (i=0; i<RSIZE; ++i) {
	for (j=0; j<GSIZE; ++j) {
	    for (k=0; k<BSIZE; ++k) {
		defs[i][j][k].red=(255 * i / (RSIZE-1)) << 8;
		defs[i][j][k].green=(255 * j / (GSIZE-1))<< 8;
		defs[i][j][k].blue=(255 * k / (BSIZE-1)) << 8;
		defs[i][j][k].flags=DoRed|DoGreen|DoBlue;
		if (!XAllocColor(dpy,cmap,&defs[i][j][k])) {
		    fprintf(stderr,"XAllocColor failed\n");
		    exit(-1);
		}
	    }
	}
    }
}

int init_xwin(int width, int height) {
    XGCValues gcv;
    XSetWindowAttributes xswa;
  
    if ((dpy = XOpenDisplay(NULL)) == NULL) {
	fprintf(stderr, "cant open display\n");
	exit(1);
    }
    scr = DefaultScreen(dpy);
    xswa.background_pixel = BlackPixel(dpy,scr);
    xswa.border_pixel = BlackPixel(dpy,scr);
    xswa.event_mask = ExposureMask | ButtonPressMask | KeyPressMask;
    win=XCreateWindow(dpy,RootWindow(dpy,scr),0,0,width,height,1,
		      CopyFromParent,CopyFromParent,CopyFromParent,
		      (CWBackPixel|CWBorderPixel|CWEventMask),&xswa);
    init_cmap();
    gcv.foreground = WhitePixel(dpy,scr);
    gcv.background = BlackPixel(dpy,scr);
    gcv.line_width = 1;
    gc = XCreateGC(dpy,win,(GCForeground|GCBackground|GCLineWidth),&gcv);
    XMapWindow(dpy,win);
}

#define N_DITH	4
int bayer[N_DITH][N_DITH] = {
    {  0,  8,  2, 10 },
    { 12,  4, 14,  6 },
    {  3, 11,  1,  9 },
    { 15,  7, 13,  5 }
};

int dither(int d,int csize,int x,int y) {
    int n,e,span;
    span = 255 / csize;
    n = d / span;
    if (n == csize) return(n);
    e = d - n * span;
    if (e * N_DITH * N_DITH
	> bayer[x%N_DITH][y%N_DITH] * span) return(n+1);
    else return(n);
}

void set_rgb(XImage *image,int x0,int y0,unsigned char *data,int w,int h) {
    int x,y;
    unsigned int r,g,b;
    unsigned long red,green,blue,pxl;
    unsigned char *s=data;

    for (y=y0; y<y0+h; ++y) {
	for (x=x0; x<x0+w; ++x) {
	    red = *s++; green = *s++; blue = *s++;
	    if (use_truecolor) {
		pxl = (red << nshift_red) + (green << nshift_green)
		    + (blue << nshift_blue);
	    } else {
		r = dither(red,RSIZE-1,x,y);
		g = dither(green,GSIZE-1,x,y);
		b = dither(blue,BSIZE-1,x,y);
		pxl = defs[r][g][b].pixel;
	    }
	    XPutPixel(image,x,y,pxl);
	}
    }
}

unsigned char *load_rgb(char *fname,int w,int h) {
    FILE *fp;
    unsigned char *data,*s;
    int i;
    if ((data=(unsigned char *)malloc(w*h*3)) == NULL) {
	fprintf(stderr,"can not malloc %d\n",w*h*3); exit(-1);
    }
    if ((fp=fopen(fname,"r")) == NULL) {
	fprintf(stderr,"can not open %s\n",fname); exit(-1);
    }
    for (i=0,s=data; i<w*h*3; ++i) {
	*s++ = (unsigned char) getc(fp);
    }
    fclose(fp);
    return(data);
}

int main(int argc, char **argv) {
    int ac=argc;
    char **av=argv;
    char *fname="sample.rgb", *fname2="face1.rgb";
    int width=WIDTH, height=HEIGHT;
    unsigned char *data,*data2;

    while (--ac) {
	++av;
	if (!strcmp(*av,"-f")) {
	    if (! --ac) goto Usage;
	    fname = *++av;
	} else if (!strcmp(*av,"-f2")) {
	    if (! --ac) goto Usage;
	    fname2 = *++av;
	} else if (!strcmp(*av,"-w")) {
	    if (! --ac) goto Usage;
	    width = atoi(*++av);
	} else if (!strcmp(*av,"-h")) {
	    if (! --ac) goto Usage;
	    height = atoi(*++av);
	} else {
	Usage:
	    fprintf(stderr,"usage: %s -w width -h height -f filename -f2 filename\n",argv[0]);
	    exit(-1);
	}
    }
    data = load_rgb(fname,width,height);
    data2 = load_rgb(fname2,16,16);
    init_xwin(width,height);
    image = init_ximage(width,height);
    image2 = init_ximage(16,16);
    set_rgb(image,0,0,data,width,height);
    set_rgb(image2,0,0,data2,16,16);
    for (;;) {
	XEvent ev;
	char s[256];
	int len, i, x2n, y2n;
	static int x2=64, y2=128;
	XNextEvent(dpy,&ev);
	switch (ev.type) {
	  case Expose:
	    XPutImage(dpy,win,gc,image,0,0,0,0,width,height);
	    XPutImage(dpy,win,gc,image2,0,0,x2,y2,16,16);
	    break;
	  case ButtonPress:
	    exit(0);
	    break;
	  case KeyPress:
	    if (!(len=XLookupString(&(ev.xkey),s,sizeof(s),NULL,NULL)))
		break;
	    x2n=x2; y2n=y2;
	    for (i=0; i<len; i++) {
		switch (s[i]) {
		  case 'h':
		    x2n=x2-16; if (x2n<0) x2n=0; break;
		  case 'l':
		    x2n=x2+16; if (x2n>=width-16) x2n=width-16; break;
		  case 'k':
		    y2n=y2-16; if (y2n<0) y2n=0; break;
		  case 'j':
		    y2n=y2+16; if (y2n>=height-16) y2n=height-16; break;
		}
	    }
	    XPutImage(dpy,win,gc,image,x2,y2,x2,y2,16,16);
	    XPutImage(dpy,win,gc,image2,0,0,x2n,y2n,16,16);
	    x2=x2n;y2=y2n;
	    break;
	  default:
	    break;
	}
    }
}