#include "TinyGL/gl_zgl.h"
#include <math.h>


/*
 * image conversion
 */
void gl_convertRGB_to_5R6G5B( unsigned short *pixmap, unsigned char *rgb, int xsize, int ysize ){
	int            i;
	int            n;
	unsigned char *p;

	p = rgb;
	n = xsize*ysize;
	for( i=0; i<n; i++ ){
		pixmap[i]  = ((p[0]&0xF8)<<8) | ((p[1]&0xFC)<<3) | ((p[2]&0xF8)>>3); 
		p         += 3;
	}
}

/*
 * linear interpolation with xf,yf normalized to 2^16
 */

#define INTERP_NORM_BITS  16
#define INTERP_NORM       (1 << INTERP_NORM_BITS)

static /*inline*/ int interpolate( int v00, int v01, int v10, int xf, int yf ){
	return v00+(((v01-v00)*xf + (v10-v00)*yf) >> INTERP_NORM_BITS);
}


/* 
 * TODO: more accurate resampling 
 */

void gl_resizeImage (unsigned char *dest, int xsize_dest, int ysize_dest, unsigned char *src, int xsize_src, int ysize_src ){
	unsigned char *pix;
	unsigned char *pix_src;
	float          x1, y1, x1inc, y1inc;
	int            xi, yi, j, xf, yf, x, y;

	pix     = dest;
	pix_src = src;
  
	x1inc = (float) (xsize_src - 1) / (float) (xsize_dest - 1);
	y1inc = (float) (ysize_src - 1) / (float) (ysize_dest - 1);

  y1=0;
  for(y=0;y<ysize_dest;y++) {
    x1=0;
    for(x=0;x<xsize_dest;x++) {
      xi=(int) x1;
      yi=(int) y1;
      xf=(int) ((x1 - floor(x1)) * INTERP_NORM);
      yf=(int) ((y1 - floor(y1)) * INTERP_NORM);
      
      if ((xf+yf) <= INTERP_NORM) {
	for(j=0;j<3;j++) {
	  pix[j]=interpolate(pix_src[(yi*xsize_src+xi)*3+j],
			     pix_src[(yi*xsize_src+xi+1)*3+j],
			     pix_src[((yi+1)*xsize_src+xi)*3+j],
			     xf,yf);
	}
      } else {
	xf=INTERP_NORM - xf;
	yf=INTERP_NORM - yf;
	for(j=0;j<3;j++) {
	  pix[j]=interpolate(pix_src[((yi+1)*xsize_src+xi+1)*3+j],
			     pix_src[((yi+1)*xsize_src+xi)*3+j],
			     pix_src[(yi*xsize_src+xi+1)*3+j],
			     xf,yf);
	}
      }
      
      pix+=3;
      x1+=x1inc;
    }
    y1+=y1inc;
  }
}

#define FRAC_BITS 16

/* resizing with no interlating nor nearest pixel */

void gl_resizeImageNoInterpolate(
	unsigned char *dest,
	int            xsize_dest,
	int            ysize_dest,
	unsigned char *src,
	int            xsize_src,
	int            ysize_src
){
	unsigned char *pix;
	unsigned char *pix_src;
	unsigned char *pix1;
	int            x1,y1,x1inc,y1inc;
	int            xi,yi,x,y;

	pix     = dest;
	pix_src = src;
  
	x1inc = (int)((float) ((xsize_src)<<FRAC_BITS) / (float) (xsize_dest));
	y1inc = (int)((float) ((ysize_src)<<FRAC_BITS) / (float) (ysize_dest));

	y1 = 0;
	for( y=0; y<ysize_dest; y++ ){
		x1 = 0;
		for( x=0; x<xsize_dest; x++ ){
			xi   = x1 >> FRAC_BITS;
			yi   = y1 >> FRAC_BITS;
			pix1 = pix_src+(yi*xsize_src+xi)*3;

			pix[0] = pix1[0];
			pix[1] = pix1[1];
			pix[2] = pix1[2];

			pix += 3;
			x1  += x1inc;
		}
		y1 += y1inc;
	}
}