/*
 *	matrix - 
 *		Use 4x4 matricies to process color images.
 *
 *	To compile:
 cc matrix.c -o matrix -lgutil -limage -lgl -lm
 *
 *				Paul Haeberli - 1993
 */
#include <math.h>
#include <stdio.h>

#define RLUM    (0.3086)
#define GLUM    (0.6094)
#define BLUM    (0.0820)

#define OFFSET_R        0
#define OFFSET_G        1
#define OFFSET_B        2
#define OFFSET_A        3

unsigned char CLAMP0255(int32_t a)
{
  return (unsigned char)
    ( (((-a) >> 31) & a)  // 0 if the number was negative
      | (255 - a) >> 31); // -1 if the number was greater than 255
}

/* 
 *	printmat -	
 *		print a 4 by 4 matrix
 */
void
printmat(mat)
  float mat[4][4];
{
  int x, y;

  fprintf(stderr,"\n");
  for(y=0; y<4; y++) {
    for(x=0; x<4; x++) 
      fprintf(stderr,"%f ",mat[y][x]);
    fprintf(stderr,"\n");
  }
  fprintf(stderr,"\n");
}

/* 
 *	applymatrix -	
 *		use a matrix to transform colors.
 */
void
applymatrix(lptr,mat,n)
  unsigned long *lptr;
float mat[4][4];
int n;
{
  int ir, ig, ib, r, g, b;
  unsigned char *cptr;

  cptr = (unsigned char *)lptr;
  while(n--) {
    ir = cptr[OFFSET_R];
    ig = cptr[OFFSET_G];
    ib = cptr[OFFSET_B];
    r = ir*mat[0][0] + ig*mat[1][0] + ib*mat[2][0] + mat[3][0];
    g = ir*mat[0][1] + ig*mat[1][1] + ib*mat[2][1] + mat[3][1];
    b = ir*mat[0][2] + ig*mat[1][2] + ib*mat[2][2] + mat[3][2];
    cptr[OFFSET_R] = CLAMP0255(r);
    cptr[OFFSET_G] = CLAMP0255(g);
    cptr[OFFSET_B] = CLAMP0255(b);
    cptr += 4;
  }
}

/* 
 *	matrixmult -	
 *		multiply two matricies
 */
void
matrixmult(a,b,c)
  float a[4][4], b[4][4], c[4][4];
{
  int x, y;
  float temp[4][4];

  for(y=0; y<4 ; y++)
    for(x=0 ; x<4 ; x++) {
      temp[y][x] = b[y][0] * a[0][x]
        + b[y][1] * a[1][x]
        + b[y][2] * a[2][x]
        + b[y][3] * a[3][x];
    }
  for(y=0; y<4; y++)
    for(x=0; x<4; x++)
      c[y][x] = temp[y][x];
}

/* 
 *	identmat -	
 *		make an identity matrix
 */
void
identmat(matrix)
  float *matrix;
{
  *matrix++ = 1.0;    /* row 1        */
  *matrix++ = 0.0;
  *matrix++ = 0.0;
  *matrix++ = 0.0;
  *matrix++ = 0.0;    /* row 2        */
  *matrix++ = 1.0;
  *matrix++ = 0.0;
  *matrix++ = 0.0;
  *matrix++ = 0.0;    /* row 3        */
  *matrix++ = 0.0;
  *matrix++ = 1.0;
  *matrix++ = 0.0;
  *matrix++ = 0.0;    /* row 4        */
  *matrix++ = 0.0;
  *matrix++ = 0.0;
  *matrix++ = 1.0;
}

/* 
 *	xformpnt -	
 *		transform a 3D point using a matrix
 */
void
xformpnt(matrix,x,y,z,tx,ty,tz)
  float matrix[4][4];
float x,y,z;
float *tx,*ty,*tz;
{
  *tx = x*matrix[0][0] + y*matrix[1][0] + z*matrix[2][0] + matrix[3][0];
  *ty = x*matrix[0][1] + y*matrix[1][1] + z*matrix[2][1] + matrix[3][1];
  *tz = x*matrix[0][2] + y*matrix[1][2] + z*matrix[2][2] + matrix[3][2];
}

/* 
 *	cscalemat -	
 *		make a color scale marix
 */
void
cscalemat(mat,rscale,gscale,bscale)
  float mat[4][4];
float rscale, gscale, bscale;
{
  float mmat[4][4];

  mmat[0][0] = rscale;
  mmat[0][1] = 0.0;
  mmat[0][2] = 0.0;
  mmat[0][3] = 0.0;

  mmat[1][0] = 0.0;
  mmat[1][1] = gscale;
  mmat[1][2] = 0.0;
  mmat[1][3] = 0.0;


  mmat[2][0] = 0.0;
  mmat[2][1] = 0.0;
  mmat[2][2] = bscale;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	lummat -	
 *		make a luminance marix
 */
void
lummat(mat)
  float mat[4][4];
{
  float mmat[4][4];
  float rwgt, gwgt, bwgt;

  rwgt = RLUM;
  gwgt = GLUM;
  bwgt = BLUM;
  mmat[0][0] = rwgt;
  mmat[0][1] = rwgt;
  mmat[0][2] = rwgt;
  mmat[0][3] = 0.0;

  mmat[1][0] = gwgt;
  mmat[1][1] = gwgt;
  mmat[1][2] = gwgt;
  mmat[1][3] = 0.0;

  mmat[2][0] = bwgt;
  mmat[2][1] = bwgt;
  mmat[2][2] = bwgt;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	saturatemat -	
 *		make a saturation marix
 */
void
saturatemat(mat,sat)
  float mat[4][4];
float sat;
{
  float mmat[4][4];
  float a, b, c, d, e, f, g, h, i;
  float rwgt, gwgt, bwgt;

  rwgt = RLUM;
  gwgt = GLUM;
  bwgt = BLUM;

  a = (1.0-sat)*rwgt + sat;
  b = (1.0-sat)*rwgt;
  c = (1.0-sat)*rwgt;
  d = (1.0-sat)*gwgt;
  e = (1.0-sat)*gwgt + sat;
  f = (1.0-sat)*gwgt;
  g = (1.0-sat)*bwgt;
  h = (1.0-sat)*bwgt;
  i = (1.0-sat)*bwgt + sat;
  mmat[0][0] = a;
  mmat[0][1] = b;
  mmat[0][2] = c;
  mmat[0][3] = 0.0;

  mmat[1][0] = d;
  mmat[1][1] = e;
  mmat[1][2] = f;
  mmat[1][3] = 0.0;

  mmat[2][0] = g;
  mmat[2][1] = h;
  mmat[2][2] = i;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	offsetmat -	
 *		offset r, g, and b
 */
void
offsetmat(mat,roffset,goffset,boffset)
  float mat[4][4];
float roffset, goffset, boffset;
{
  float mmat[4][4];

  mmat[0][0] = 1.0;
  mmat[0][1] = 0.0;
  mmat[0][2] = 0.0;
  mmat[0][3] = 0.0;

  mmat[1][0] = 0.0;
  mmat[1][1] = 1.0;
  mmat[1][2] = 0.0;
  mmat[1][3] = 0.0;

  mmat[2][0] = 0.0;
  mmat[2][1] = 0.0;
  mmat[2][2] = 1.0;
  mmat[2][3] = 0.0;

  mmat[3][0] = roffset;
  mmat[3][1] = goffset;
  mmat[3][2] = boffset;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	xrotate -	
 *		rotate about the x (red) axis
 */
void
xrotatemat(mat,rs,rc)
  float mat[4][4];
float rs, rc;
{
  float mmat[4][4];

  mmat[0][0] = 1.0;
  mmat[0][1] = 0.0;
  mmat[0][2] = 0.0;
  mmat[0][3] = 0.0;

  mmat[1][0] = 0.0;
  mmat[1][1] = rc;
  mmat[1][2] = rs;
  mmat[1][3] = 0.0;

  mmat[2][0] = 0.0;
  mmat[2][1] = -rs;
  mmat[2][2] = rc;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	yrotate -	
 *		rotate about the y (green) axis
 */
void
yrotatemat(mat,rs,rc)
  float mat[4][4];
float rs, rc;
{
  float mmat[4][4];

  mmat[0][0] = rc;
  mmat[0][1] = 0.0;
  mmat[0][2] = -rs;
  mmat[0][3] = 0.0;

  mmat[1][0] = 0.0;
  mmat[1][1] = 1.0;
  mmat[1][2] = 0.0;
  mmat[1][3] = 0.0;

  mmat[2][0] = rs;
  mmat[2][1] = 0.0;
  mmat[2][2] = rc;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	zrotate -	
 *		rotate about the z (blue) axis
 */
void
zrotatemat(mat,rs,rc)
  float mat[4][4];
float rs, rc;
{
  float mmat[4][4];

  mmat[0][0] = rc;
  mmat[0][1] = rs;
  mmat[0][2] = 0.0;
  mmat[0][3] = 0.0;

  mmat[1][0] = -rs;
  mmat[1][1] = rc;
  mmat[1][2] = 0.0;
  mmat[1][3] = 0.0;

  mmat[2][0] = 0.0;
  mmat[2][1] = 0.0;
  mmat[2][2] = 1.0;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	zshear -	
 *		shear z using x and y.
 */
void
zshearmat(mat,dx,dy)
  float mat[4][4];
float dx, dy;
{
  float mmat[4][4];

  mmat[0][0] = 1.0;
  mmat[0][1] = 0.0;
  mmat[0][2] = dx;
  mmat[0][3] = 0.0;

  mmat[1][0] = 0.0;
  mmat[1][1] = 1.0;
  mmat[1][2] = dy;
  mmat[1][3] = 0.0;

  mmat[2][0] = 0.0;
  mmat[2][1] = 0.0;
  mmat[2][2] = 1.0;
  mmat[2][3] = 0.0;

  mmat[3][0] = 0.0;
  mmat[3][1] = 0.0;
  mmat[3][2] = 0.0;
  mmat[3][3] = 1.0;
  matrixmult(mmat,mat,mat);
}

/* 
 *	simplehuerotatemat -	
 *		simple hue rotation. This changes luminance 
 */
void
simplehuerotatemat(mat,rot)
  float mat[4][4];
float rot;
{
  float mag;
  float xrs, xrc;
  float yrs, yrc;
  float zrs, zrc;

  /* rotate the grey vector into positive Z */
  mag = sqrt(2.0);
  xrs = 1.0/mag;
  xrc = 1.0/mag;
  xrotatemat(mat,xrs,xrc);

  mag = sqrt(3.0);
  yrs = -1.0/mag;
  yrc = sqrt(2.0)/mag;
  yrotatemat(mat,yrs,yrc);

  /* rotate the hue */
  zrs = sin(rot*M_PI/180.0);
  zrc = cos(rot*M_PI/180.0);
  zrotatemat(mat,zrs,zrc);

  /* rotate the grey vector back into place */
  yrotatemat(mat,-yrs,yrc);
  xrotatemat(mat,-xrs,xrc);
}

/* 
 *	huerotatemat -	
 *		rotate the hue, while maintaining luminance.
 */
void
huerotatemat(mat,rot)
  float mat[4][4];
float rot;
{
  float mmat[4][4];
  float mag;
  float lx, ly, lz;
  float xrs, xrc;
  float yrs, yrc;
  float zrs, zrc;
  float zsx, zsy;

  identmat(mmat);

  /* rotate the grey vector into positive Z */
  mag = sqrt(2.0);
  xrs = 1.0/mag;
  xrc = 1.0/mag;
  xrotatemat(mmat,xrs,xrc);
  mag = sqrt(3.0);
  yrs = -1.0/mag;
  yrc = sqrt(2.0)/mag;
  yrotatemat(mmat,yrs,yrc);

  /* shear the space to make the luminance plane horizontal */
  xformpnt(mmat,RLUM,GLUM,BLUM,&lx,&ly,&lz);
  zsx = lx/lz;
  zsy = ly/lz;
  zshearmat(mmat,zsx,zsy);

  /* rotate the hue */
  zrs = sin(rot*M_PI/180.0);
  zrc = cos(rot*M_PI/180.0);
  zrotatemat(mmat,zrs,zrc);

  /* unshear the space to put the luminance plane back */
  zshearmat(mmat,-zsx,-zsy);

  /* rotate the grey vector back into place */
  yrotatemat(mmat,-yrs,yrc);
  xrotatemat(mmat,-xrs,xrc);

  matrixmult(mmat,mat,mat);
}
