Initial revision

[imager.git] / image.c

#include "image.h"
#include "io.h"

/*
=head1 NAME

image.c - implements most of the basic functions of Imager and much of the rest

=head1 SYNOPSIS

  i_img *i;
  i_color *c;
  c = i_color_new(red, green, blue, alpha);
  ICL_DESTROY(c);
  i = i_img_new();
  i_img_destroy(i);
  // and much more

=head1 DESCRIPTION

image.c implements the basic functions to create and destroy image and
color objects for Imager.

=head1 FUNCTION REFERENCE

Some of these functions are internal.

=over 4

=cut
*/

#define XAXIS 0
#define YAXIS 1

#define minmax(a,b,i) ( ((a>=i)?a: ( (b<=i)?b:i   )) )

/* Hack around an obscure linker bug on solaris - probably due to builtin gcc thingies */
void fake() { ceil(1); }

/* 
=item ICL_new_internal(r, g, b, a)

Return a new color object with values passed to it.

   r - red   component (range: 0 - 255)
   g - green component (range: 0 - 255)
   b - blue  component (range: 0 - 255)
   a - alpha component (range: 0 - 255)

=cut
*/

i_color *
ICL_new_internal(unsigned char r,unsigned char g,unsigned char b,unsigned char a) {
  i_color *cl=NULL;

  mm_log((1,"ICL_new_internal(r %d,g %d,b %d,a %d)\n",cl,r,g,b,a));

  if ( (cl=mymalloc(sizeof(i_color))) == NULL) m_fatal(2,"malloc() error\n");
  cl->rgba.r=r;
  cl->rgba.g=g;
  cl->rgba.b=b;
  cl->rgba.a=a;
  mm_log((1,"(0x%x) <- ICL_new_internal\n",cl));
  return cl;
}


/*
=item ICL_set_internal(cl, r, g, b, a)

 Overwrite a color with new values.

   cl - pointer to color object
   r - red   component (range: 0 - 255)
   g - green component (range: 0 - 255)
   b - blue  component (range: 0 - 255)
   a - alpha component (range: 0 - 255)

=cut
*/

i_color *
ICL_set_internal(i_color *cl,unsigned char r,unsigned char g,unsigned char b,unsigned char a) {
  mm_log((1,"ICL_set_internal(cl* 0x%x,r %d,g %d,b %d,a %d)\n",cl,r,g,b,a));
  if (cl == NULL)
    if ( (cl=mymalloc(sizeof(i_color))) == NULL)
      m_fatal(2,"malloc() error\n");
  cl->rgba.r=r;
  cl->rgba.g=g;
  cl->rgba.b=b;
  cl->rgba.a=a;
  mm_log((1,"(0x%x) <- ICL_set_internal\n",cl));
  return cl;
}


/* 
=item ICL_add(dst, src, ch)

Add src to dst inplace - dst is modified.

   dst - pointer to destination color object
   src - pointer to color object that is added
   ch - number of channels

=cut
*/

void
ICL_add(i_color *dst,i_color *src,int ch) {
  int tmp,i;
  for(i=0;i<ch;i++) {
    tmp=dst->channel[i]+src->channel[i];
    dst->channel[i]= tmp>255 ? 255:tmp;
  }
}

/* 
=item ICL_info(cl)

Dump color information to log - strictly for debugging.

   cl - pointer to color object

=cut
*/

void
ICL_info(i_color *cl) {
  mm_log((1,"i_color_info(cl* 0x%x)\n",cl));
  mm_log((1,"i_color_info: (%d,%d,%d,%d)\n",cl->rgba.r,cl->rgba.g,cl->rgba.b,cl->rgba.a));
}

/* 
=item ICL_DESTROY

Destroy ancillary data for Color object.

   cl - pointer to color object

=cut
*/

void
ICL_DESTROY(i_color *cl) {
  mm_log((1,"ICL_DESTROY(cl* 0x%x)\n",cl));
  myfree(cl);
}

/*
=item IIM_new(x, y, ch)

Creates a new image object I<x> pixels wide, and I<y> pixels high with I<ch> channels.

=cut
*/


i_img *
IIM_new(int x,int y,int ch) {
  i_img *im;
  mm_log((1,"IIM_new(x %d,y %d,ch %d)\n",x,y,ch));

  im=i_img_empty_ch(NULL,x,y,ch);
  
  mm_log((1,"(0x%x) <- IIM_new\n",im));
  return im;
}


void
IIM_DESTROY(i_img *im) {
  mm_log((1,"IIM_DESTROY(im* 0x%x)\n",im));
  /*   myfree(cl); */
}



/* 
=item i_img_new()

Create new image reference - notice that this isn't an object yet and
this should be fixed asap.

=cut
*/


i_img *
i_img_new() {
  i_img *im;
  
  mm_log((1,"i_img_struct()\n"));
  if ( (im=mymalloc(sizeof(i_img))) == NULL)
    m_fatal(2,"malloc() error\n");
  
  im->xsize=0;
  im->ysize=0;
  im->channels=3;
  im->ch_mask=MAXINT;
  im->bytes=0;
  im->data=NULL;

  im->i_f_ppix=i_ppix_d;
  im->i_f_gpix=i_gpix_d;
  im->ext_data=NULL;
  
  mm_log((1,"(0x%x) <- i_img_struct\n",im));
  return im;
}

/* 
=item i_img_empty(im, x, y)

Re-new image reference (assumes 3 channels)

   im - Image pointer
   x - xsize of destination image
   y - ysize of destination image

=cut
*/

i_img *
i_img_empty(i_img *im,int x,int y) {
  mm_log((1,"i_img_empty(*im 0x%x,x %d,y %d)\n",im,x,y));
  if (im==NULL)
    if ( (im=mymalloc(sizeof(i_img))) == NULL)
      m_fatal(2,"malloc() error\n");
  
  im->xsize=x;
  im->ysize=y;
  im->channels=3;
  im->ch_mask=MAXINT;
  im->bytes=x*y*im->channels;
  if ( (im->data=mymalloc(im->bytes)) == NULL) m_fatal(2,"malloc() error\n"); 
  memset(im->data,0,(size_t)im->bytes);

  im->i_f_ppix=i_ppix_d;
  im->i_f_gpix=i_gpix_d;
  im->ext_data=NULL;
  
  mm_log((1,"(0x%x) <- i_img_empty\n",im));
  return im;
}

/* 
=item i_img_empty_ch(im, x, y, ch)

Re-new image reference 

   im - Image pointer
   x - xsize of destination image
   y - ysize of destination image
   ch - number of channels

=cut
*/

i_img *
i_img_empty_ch(i_img *im,int x,int y,int ch) {
  mm_log((1,"i_img_empty_ch(*im 0x%x,x %d,y %d,ch %d)\n",im,x,y,ch));
  if (im==NULL)
    if ( (im=mymalloc(sizeof(i_img))) == NULL)
      m_fatal(2,"malloc() error\n");
  
  im->xsize=x;
  im->ysize=y;
  im->channels=ch;
  im->ch_mask=MAXINT;
  im->bytes=x*y*im->channels;
  if ( (im->data=mymalloc(im->bytes)) == NULL) m_fatal(2,"malloc() error\n"); 
  memset(im->data,0,(size_t)im->bytes);
  
  im->i_f_ppix=i_ppix_d;
  im->i_f_gpix=i_gpix_d;
  im->ext_data=NULL;
  
  mm_log((1,"(0x%x) <- i_img_empty_ch\n",im));
  return im;
}

/* 
=item i_img_exorcise(im)

Free image data.

   im - Image pointer

=cut
*/

void
i_img_exorcise(i_img *im) {
  mm_log((1,"i_img_exorcise(im* 0x%x)\n",im));
  if (im->data != NULL) { myfree(im->data); }
  im->data=NULL;
  im->xsize=0;
  im->ysize=0;
  im->channels=0;

  im->i_f_ppix=i_ppix_d;
  im->i_f_gpix=i_gpix_d;
  im->ext_data=NULL;
}

/* 
=item i_img_destroy(im)

Destroy image and free data via exorcise.

   im - Image pointer

=cut
*/

void
i_img_destroy(i_img *im) {
  mm_log((1,"i_img_destroy(im* 0x%x)\n",im));
  i_img_exorcise(im);
  if (im) { myfree(im); }
}

/* 
=item i_img_info(im, info)

Return image information

   im - Image pointer
   info - pointer to array to return data

info is an array of 4 integers with the following values:

 info[0] - width
 info[1] - height
 info[2] - channels
 info[3] - channel mask

=cut
*/


void
i_img_info(i_img *im,int *info) {
  mm_log((1,"i_img_info(im 0x%x)\n",im));
  if (im != NULL) {
    mm_log((1,"i_img_info: xsize=%d ysize=%d channels=%d mask=%ud\n",im->xsize,im->ysize,im->channels,im->ch_mask));
    mm_log((1,"i_img_info: data=0x%d\n",im->data));
    info[0]=im->xsize;
    info[1]=im->ysize;
    info[2]=im->channels;
    info[3]=im->ch_mask;
  } else {
    info[0]=0;
    info[1]=0;
    info[2]=0;
    info[3]=0;
  }
}

/*
=item i_img_setmask(im, ch_mask)

Set the image channel mask for I<im> to I<ch_mask>.

=cut
*/
void
i_img_setmask(i_img *im,int ch_mask) { im->ch_mask=ch_mask; }


/*
=item i_img_getmask(im)

Get the image channel mask for I<im>.

=cut
*/
int
i_img_getmask(i_img *im) { return im->ch_mask; }

/*
=item i_img_getchannels(im)

Get the number of channels in I<im>.

=cut
*/
int
i_img_getchannels(i_img *im) { return im->channels; }


/*
=item i_ppix(im, x, y, col)

Sets the pixel at (I<x>,I<y>) in I<im> to I<col>.

Returns true if the pixel could be set, false if x or y is out of
range.

=cut
*/
int
i_ppix(i_img *im,int x,int y,i_color *val) { return im->i_f_ppix(im,x,y,val); }

/*
=item i_gpix(im, x, y, &col)

Get the pixel at (I<x>,I<y>) in I<im> into I<col>.

Returns true if the pixel could be retrieved, false otherwise.

=cut
*/
int
i_gpix(i_img *im,int x,int y,i_color *val) { return im->i_f_gpix(im,x,y,val); }

/*
=item i_ppix_d(im, x, y, col)

Internal function.

This is the function kept in the i_f_ppix member of an i_img object.
It does a normal store of a pixel into the image with range checking.

Returns true if the pixel could be set, false otherwise.

=cut
*/
int
i_ppix_d(i_img *im,int x,int y,i_color *val) {
  int ch;
  
  if ( x>-1 && x<im->xsize && y>-1 && y<im->ysize ) {
    for(ch=0;ch<im->channels;ch++)
      if (im->ch_mask&(1<<ch)) 
	im->data[(x+y*im->xsize)*im->channels+ch]=val->channel[ch];
    return 0;
  }
  return -1; /* error was clipped */
}

/*
=item i_gpix_d(im, x, y, &col)

Internal function.

This is the function kept in the i_f_gpix member of an i_img object.
It does normal retrieval of a pixel from the image with range checking.

Returns true if the pixel could be set, false otherwise.

=cut
*/
int 
i_gpix_d(i_img *im,int x,int y,i_color *val) {
  int ch;
  if (x>-1 && x<im->xsize && y>-1 && y<im->ysize) {
    for(ch=0;ch<im->channels;ch++) 
    	val->channel[ch]=im->data[(x+y*im->xsize)*im->channels+ch];
    return 0;
  }
  return -1; /* error was cliped */
}

/*
=item i_ppix_pch(im, x, y, ch)

Get the value from the channel I<ch> for pixel (I<x>,I<y>) from I<im>
scaled to [0,1].

Returns zero if x or y is out of range.

Warning: this ignores the vptr interface for images.

=cut
*/
float
i_gpix_pch(i_img *im,int x,int y,int ch) {
  if (x>-1 && x<im->xsize && y>-1 && y<im->ysize) return ((float)im->data[(x+y*im->xsize)*im->channels+ch]/255);
  else return 0;
}


/*
=item i_copyto_trans(im, src, x1, y1, x2, y2, tx, ty, trans)

(x1,y1) (x2,y2) specifies the region to copy (in the source coordinates)
(tx,ty) specifies the upper left corner for the target image.
pass NULL in trans for non transparent i_colors.

=cut
*/

void
i_copyto_trans(i_img *im,i_img *src,int x1,int y1,int x2,int y2,int tx,int ty,i_color *trans) {
  i_color pv;
  int x,y,t,ttx,tty,tt,ch;

  mm_log((1,"i_copyto_trans(im* 0x%x,src 0x%x,x1 %d,y1 %d,x2 %d,y2 %d,tx %d,ty %d,trans* 0x%x)\n",im,src,x1,y1,x2,y2,tx,ty,trans));

  if (x2<x1) { t=x1; x1=x2; x2=t; }
  if (y2<y1) { t=y1; y1=y2; y2=t; }

  ttx=tx;
  for(x=x1;x<x2;x++)
    {
      tty=ty;
      for(y=y1;y<y2;y++)
	{
	  i_gpix(src,x,y,&pv);
	  if ( trans != NULL)
	  {
	    tt=0;
	    for(ch=0;ch<im->channels;ch++) if (trans->channel[ch]!=pv.channel[ch]) tt++;
	    if (tt) i_ppix(im,ttx,tty,&pv);
	  } else i_ppix(im,ttx,tty,&pv);
	  tty++;
	}
      ttx++;
    }
}

/*
=item i_copyto(dest, src, x1, y1, x2, y2, tx, ty)

Copies image data from the area (x1,y1)-[x2,y2] in the source image to
a rectangle the same size with it's top-left corner at (tx,ty) in the
destination image.

If x1 > x2 or y1 > y2 then the corresponding co-ordinates are swapped.

=cut
*/

void
i_copyto(i_img *im,i_img *src,int x1,int y1,int x2,int y2,int tx,int ty) {
  i_color pv;
  int x,y,t,ttx,tty;

  if (x2<x1) { t=x1; x1=x2; x2=t; }
  if (y2<y1) { t=y1; y1=y2; y2=t; }

  mm_log((1,"i_copyto(im* 0x%x,src 0x%x,x1 %d,y1 %d,x2 %d,y2 %d,tx %d,ty %d)\n",im,src,x1,y1,x2,y2,tx,ty));

    tty=ty;
    for(y=y1;y<y2;y++) {
    ttx=tx;
    for(x=x1;x<x2;x++) {
      i_gpix(src,x,y,&pv);
      i_ppix(im,ttx,tty,&pv);
    ttx++;
    }
    tty++;
  }
}

/*
=item i_copy(im, src)

Copies the contents of the image I<src> over the image I<im>.

=cut
*/

void
i_copy(i_img *im,i_img *src) {
  i_color pv;
  int x,y,y1,x1;

  mm_log((1,"i_copy(im* 0x%x,src 0x%x)\n",im,src));

  x1=src->xsize;
  y1=src->ysize;
  i_img_empty_ch(im,x1,y1,src->channels);
  
  for(y=0;y<y1;y++) for(x=0;x<x1;x++) {
    i_gpix(src,x,y,&pv);
    i_ppix(im,x,y,&pv);
  }
}


/*
=item i_rubthru(im, src, tx, ty)

Takes the image I<src> and applies it at an original (I<tx>,I<ty>) in I<im>.

The alpha channel of each pixel in I<src> is used to control how much
the existing colour in I<im> is replaced, if it is 255 then the colour
is completely replaced, if it is 0 then the original colour is left 
unmodified.

=cut
*/
void
i_rubthru(i_img *im,i_img *src,int tx,int ty) {
  i_color pv,orig,dest;
  int x,y,ttx,tty;

  mm_log((1,"i_rubthru(im 0x%x,src 0x%x,tx %d,ty %d)\n",im,src,tx,ty));

  if (im->channels != 3) {  fprintf(stderr,"Destination is not in rgb mode.\n"); exit(3); }
  if (src->channels != 4) { fprintf(stderr,"Source is not in rgba mode.\n"); exit(3); }

  ttx=tx;
  for(x=0;x<src->xsize;x++)
    {
      tty=ty;
      for(y=0;y<src->ysize;y++)
	{
	  /* fprintf(stderr,"reading (%d,%d) writing (%d,%d).\n",x,y,ttx,tty); */
	  i_gpix(src,x,y,&pv);
	  i_gpix(im,ttx,tty,&orig);
	  dest.rgb.r=(pv.rgba.a*pv.rgba.r+(255-pv.rgba.a)*orig.rgb.r)/255;
	  dest.rgb.g=(pv.rgba.a*pv.rgba.g+(255-pv.rgba.a)*orig.rgb.g)/255;
	  dest.rgb.b=(pv.rgba.a*pv.rgba.b+(255-pv.rgba.a)*orig.rgb.b)/255;
	  i_ppix(im,ttx,tty,&dest);
	  tty++;
	}
      ttx++;
    }
}

float
Lanczos(float x) {
  float PIx, PIx2;
  
  PIx = PI * x;
  PIx2 = PIx / 2.0;
  
  if ((x >= 2.0) || (x <= -2.0)) return (0.0);
  else if (x == 0.0) return (1.0);
  else return(sin(PIx) / PIx * sin(PIx2) / PIx2);
}

/*
=item i_scaleaxis(im, value, axis)

Returns a new image object which is I<im> scaled by I<value> along
wither the x-axis (I<axis> == 0) or the y-axis (I<axis> == 1).

=cut
*/

i_img*
i_scaleaxis(i_img *im, float Value, int Axis) {
  int hsize, vsize, i, j, k, l, lMax, iEnd, jEnd;
  int LanczosWidthFactor;
  float *l0, *l1, OldLocation;
  int T, TempJump1, TempJump2;
  float F, PictureValue[MAXCHANNELS];
  short psave;
  i_color val,val1,val2;
  i_img *new_img;

  mm_log((1,"i_scaleaxis(im 0x%x,Value %.2f,Axis %d)\n",im,Value,Axis));

  if (Axis == XAXIS) {
    hsize = (int) ((float) im->xsize * Value);
    vsize = im->ysize;
    
    jEnd = hsize;
    iEnd = vsize;
    
    TempJump1 = (hsize - 1) * 3;
    TempJump2 = hsize * (vsize - 1) * 3 + TempJump1;
  } else {
    hsize = im->xsize;
    vsize = (int) ((float) im->ysize * Value);
    
    jEnd = vsize;
    iEnd = hsize;
    
    TempJump1 = 0;
    TempJump2 = 0;
  }
  
  new_img=i_img_empty_ch(NULL,hsize,vsize,im->channels);
  
  if (Value >=1) LanczosWidthFactor = 1;
  else LanczosWidthFactor = (int) (1.0/Value);
  
  lMax = LanczosWidthFactor << 1;
  
  l0 = (float *) mymalloc(lMax * sizeof(float));
  l1 = (float *) mymalloc(lMax * sizeof(float));
  
  for (j=0; j<jEnd; j++) {
    OldLocation = ((float) j) / Value;
    T = (int) (OldLocation);
    F = OldLocation - (float) T;
    
    for (l = 0; l < lMax; l++) {
      l0[lMax-l-1] = Lanczos(((float) (lMax-l-1) + F) / (float) LanczosWidthFactor);
      l1[l] = Lanczos(((float) (l + 1) - F) / (float) LanczosWidthFactor);
    }
    
    if (Axis== XAXIS) {
      
      for (i=0; i<iEnd; i++) {
	for (k=0; k<im->channels; k++) PictureValue[k] = 0.0;
	for (l=0; l < lMax; l++) {
	  i_gpix(im,T+l+1, i, &val1);
	  i_gpix(im,T-lMax+l+1, i, &val2);
	  for (k=0; k<im->channels; k++) {
	    PictureValue[k] += l1[l] * val1.channel[k];
	    PictureValue[k] += l0[lMax-l-1] * val2.channel[k];
	  }
	}
	for(k=0;k<im->channels;k++) {
	  psave = (short)( PictureValue[k] / LanczosWidthFactor);
	  val.channel[k]=minmax(0,255,psave);
	}
	i_ppix(new_img,j,i,&val);
      }
      
    } else {
      
      for (i=0; i<iEnd; i++) {
	for (k=0; k<im->channels; k++) PictureValue[k] = 0.0;
	for (l=0; l < lMax; l++) {
	  i_gpix(im,i, T+l+1, &val1);
	  i_gpix(im,i, T-lMax+l+1, &val2);
	  for (k=0; k<im->channels; k++) {
	    PictureValue[k] += l1[l] * val1.channel[k];
	    PictureValue[k] += l0[lMax-l-1] * val2.channel[k]; 
	  }
	}
	for (k=0; k<im->channels; k++) {
	  psave = (short)( PictureValue[k] / LanczosWidthFactor);
	  val.channel[k]=minmax(0,255,psave);
	}
	i_ppix(new_img,i,j,&val);
      }
      
    }
  }
  myfree(l0);
  myfree(l1);

  mm_log((1,"(0x%x) <- i_scaleaxis\n",new_img));

  return new_img;
}


/* 
=item i_scale_nn(im, scx, scy)

Scale by using nearest neighbor 
Both axes scaled at the same time since 
nothing is gained by doing it in two steps 

=cut
*/


i_img*
i_scale_nn(i_img *im, float scx, float scy) {

  int nxsize,nysize,nx,ny;
  i_img *new_img;
  i_color val;

  mm_log((1,"i_scale_nn(im 0x%x,scx %.2f,scy %.2f)\n",im,scx,scy));

  nxsize = (int) ((float) im->xsize * scx);
  nysize = (int) ((float) im->ysize * scy);
    
  new_img=i_img_empty_ch(NULL,nxsize,nysize,im->channels);
  
  for(ny=0;ny<nysize;ny++) for(nx=0;nx<nxsize;nx++) {
    i_gpix(im,((float)nx)/scx,((float)ny)/scy,&val);
    i_ppix(new_img,nx,ny,&val);
  }

  mm_log((1,"(0x%x) <- i_scale_nn\n",new_img));

  return new_img;
}


/*
=item i_transform(im, opx, opxl, opy, opyl, parm, parmlen)

Spatially transforms I<im> returning a new image.

opx for a length of opxl and opy for a length of opy are arrays of
operators that modify the x and y positions to retreive the pixel data from.

parm and parmlen define extra parameters that the operators may use.

Note that this function is largely superseded by the more flexible
L<transform.c/i_transform2>.

Returns the new image.

The operators for this function are defined in L<stackmach.c>.

=cut
*/
i_img*
i_transform(i_img *im, int *opx,int opxl,int *opy,int opyl,double parm[],int parmlen) {
  double rx,ry;
  int nxsize,nysize,nx,ny;
  i_img *new_img;
  i_color val;
  
  mm_log((1,"i_transform(im 0x%x, opx 0x%x, opxl %d, opy 0x%x, opyl %d, parm 0x%x, parmlen %d)\n",im,opx,opxl,opy,opyl,parm,parmlen));

  nxsize = im->xsize;
  nysize = im->ysize ;
  
  new_img=i_img_empty_ch(NULL,nxsize,nysize,im->channels);
  /*   fprintf(stderr,"parm[2]=%f\n",parm[2]);   */
  for(ny=0;ny<nysize;ny++) for(nx=0;nx<nxsize;nx++) {
    /*     parm[parmlen-2]=(double)nx;
	   parm[parmlen-1]=(double)ny; */

    parm[0]=(double)nx;
    parm[1]=(double)ny;

    /*     fprintf(stderr,"(%d,%d) ->",nx,ny);  */
    rx=op_run(opx,opxl,parm,parmlen);
    ry=op_run(opy,opyl,parm,parmlen);
    /*    fprintf(stderr,"(%f,%f)\n",rx,ry); */
    i_gpix(im,rx,ry,&val);
    i_ppix(new_img,nx,ny,&val);
  }

  mm_log((1,"(0x%x) <- i_transform\n",new_img));
  return new_img;
}

/*
=item i_img_diff(im1, im2)

Calculates the sum of the squares of the differences between
correspoding channels in two images.

If the images are not the same size then only the common area is 
compared, hence even if images are different sizes this function 
can return zero.

=cut
*/
float
i_img_diff(i_img *im1,i_img *im2) {
  int x,y,ch,xb,yb,chb;
  float tdiff;
  i_color val1,val2;

  mm_log((1,"i_img_diff(im1 0x%x,im2 0x%x)\n",im1,im2));

  xb=(im1->xsize<im2->xsize)?im1->xsize:im2->xsize;
  yb=(im1->ysize<im2->ysize)?im1->ysize:im2->ysize;
  chb=(im1->channels<im2->channels)?im1->channels:im2->channels;

  mm_log((1,"i_img_diff: xb=%d xy=%d chb=%d\n",xb,yb,chb));

  tdiff=0;
  for(y=0;y<yb;y++) for(x=0;x<xb;x++) {
    i_gpix(im1,x,y,&val1);
    i_gpix(im2,x,y,&val2);

    for(ch=0;ch<chb;ch++) tdiff+=(val1.channel[ch]-val2.channel[ch])*(val1.channel[ch]-val2.channel[ch]);
  }
  mm_log((1,"i_img_diff <- (%.2f)\n",tdiff));
  return tdiff;
}

/* just a tiny demo of haar wavelets */

i_img*
i_haar(i_img *im) {
  int mx,my;
  int fx,fy;
  int x,y;
  int ch,c;
  i_img *new_img,*new_img2;
  i_color val1,val2,dval1,dval2;
  
  mx=im->xsize;
  my=im->ysize;
  fx=(mx+1)/2;
  fy=(my+1)/2;


  /* horizontal pass */
  
  new_img=i_img_empty_ch(NULL,fx*2,fy*2,im->channels);
  new_img2=i_img_empty_ch(NULL,fx*2,fy*2,im->channels);

  c=0; 
  for(y=0;y<my;y++) for(x=0;x<fx;x++) {
    i_gpix(im,x*2,y,&val1);
    i_gpix(im,x*2+1,y,&val2);
    for(ch=0;ch<im->channels;ch++) {
      dval1.channel[ch]=(val1.channel[ch]+val2.channel[ch])/2;
      dval2.channel[ch]=(255+val1.channel[ch]-val2.channel[ch])/2;
    }
    i_ppix(new_img,x,y,&dval1);
    i_ppix(new_img,x+fx,y,&dval2);
  }

  for(y=0;y<fy;y++) for(x=0;x<mx;x++) {
    i_gpix(new_img,x,y*2,&val1);
    i_gpix(new_img,x,y*2+1,&val2);
    for(ch=0;ch<im->channels;ch++) {
      dval1.channel[ch]=(val1.channel[ch]+val2.channel[ch])/2;
      dval2.channel[ch]=(255+val1.channel[ch]-val2.channel[ch])/2;
    }
    i_ppix(new_img2,x,y,&dval1);
    i_ppix(new_img2,x,y+fy,&dval2);
  }

  i_img_destroy(new_img);
  return new_img2;
}

/* 
=item i_count_colors(im, maxc)

returns number of colors or -1 
to indicate that it was more than max colors

=cut
*/
int
i_count_colors(i_img *im,int maxc) {
  struct octt *ct;
  int x,y;
  int xsize,ysize;
  i_color val;
  int colorcnt;

  mm_log((1,"i_count_colors(im 0x%08X,maxc %d)\n"));

  xsize=im->xsize; 
  ysize=im->ysize;
  ct=octt_new();
 
  colorcnt=0;
  for(y=0;y<ysize;y++) for(x=0;x<xsize;x++) {
    i_gpix(im,x,y,&val);
    colorcnt+=octt_add(ct,val.rgb.r,val.rgb.g,val.rgb.b);
    if (colorcnt > maxc) { octt_delete(ct); return -1; }
  }
  octt_delete(ct);
  return colorcnt;
}


symbol_table_t symbol_table={i_has_format,ICL_set_internal,ICL_info,
			     i_img_new,i_img_empty,i_img_empty_ch,i_img_exorcise,
			     i_img_info,i_img_setmask,i_img_getmask,i_ppix,i_gpix,
			     i_box,i_draw,i_arc,i_copyto,i_copyto_trans,i_rubthru};


/*
=item i_gen_reader(i_gen_read_data *info, char *buf, int length)

Performs general read buffering for file readers that permit reading
to be done through a callback.

The final callback gets two parameters, a I<need> value, and a I<want>
value, where I<need> is the amount of data that the file library needs
to read, and I<want> is the amount of space available in the buffer
maintained by these functions.

This means if you need to read from a stream that you don't know the
length of, you can return I<need> bytes, taking the performance hit of
possibly expensive callbacks (eg. back to perl code), or if you are
reading from a stream where it doesn't matter if some data is lost, or
if the total length of the stream is known, you can return I<want>
bytes.

=cut 
*/

int
i_gen_reader(i_gen_read_data *gci, char *buf, int length) {
  int total;

  if (length < gci->length - gci->cpos) {
    /* simplest case */
    memcpy(buf, gci->buffer+gci->cpos, length);
    gci->cpos += length;
    return length;
  }
  
  total = 0;
  memcpy(buf, gci->buffer+gci->cpos, gci->length-gci->cpos);
  total  += gci->length - gci->cpos;
  length -= gci->length - gci->cpos;
  buf    += gci->length - gci->cpos;
  if (length < (int)sizeof(gci->buffer)) {
    int did_read;
    int copy_size;
    while (length
	   && (did_read = (gci->cb)(gci->userdata, gci->buffer, length, 
				    sizeof(gci->buffer))) > 0) {
      gci->cpos = 0;
      gci->length = did_read;

      copy_size = min(length, gci->length);
      memcpy(buf, gci->buffer, copy_size);
      gci->cpos += copy_size;
      buf += copy_size;
      total += copy_size;
      length -= copy_size;
    }
  }
  else {
    /* just read the rest - too big for our buffer*/
    int did_read;
    while ((did_read = (gci->cb)(gci->userdata, buf, length, length)) > 0) {
      length -= did_read;
      total += did_read;
      buf += did_read;
    }
  }
  return total;
}

/*
=item i_gen_read_data_new(i_read_callback_t cb, char *userdata)

For use by callback file readers to initialize the reader buffer.

Allocates, initializes and returns the reader buffer.

See also L<image.c/free_gen_read_data> and L<image.c/i_gen_reader>.

=cut
*/
i_gen_read_data *
i_gen_read_data_new(i_read_callback_t cb, char *userdata) {
  i_gen_read_data *self = mymalloc(sizeof(i_gen_read_data));
  self->cb = cb;
  self->userdata = userdata;
  self->length = 0;
  self->cpos = 0;

  return self;
}

/*
=item free_gen_read_data(i_gen_read_data *)

Cleans up.

=cut
*/
void free_gen_read_data(i_gen_read_data *self) {
  myfree(self);
}

/*
=item i_gen_writer(i_gen_write_data *info, char const *data, int size)

Performs write buffering for a callback based file writer.

Failures are considered fatal, if a write fails then data will be
dropped.

=cut
*/
int 
i_gen_writer(
i_gen_write_data *self, 
char const *data, 
int size)
{
  if (self->filledto && self->filledto+size > self->maxlength) {
    if (self->cb(self->userdata, self->buffer, self->filledto)) {
      self->filledto = 0;
    }
    else {
      self->filledto = 0;
      return 0;
    }
  }
  if (self->filledto+size <= self->maxlength) {
    /* just save it */
    memcpy(self->buffer+self->filledto, data, size);
    self->filledto += size;
    return 1;
  }
  /* doesn't fit - hand it off */
  return self->cb(self->userdata, data, size);
}

/*
=item i_gen_write_data_new(i_write_callback_t cb, char *userdata, int max_length)

Allocates and initializes the data structure used by i_gen_writer.

This should be released with L<image.c/free_gen_write_data>

=cut
*/
i_gen_write_data *i_gen_write_data_new(i_write_callback_t cb, 
				       char *userdata, int max_length)
{
  i_gen_write_data *self = mymalloc(sizeof(i_gen_write_data));
  self->cb = cb;
  self->userdata = userdata;
  self->maxlength = min(max_length, sizeof(self->buffer));
  if (self->maxlength < 0)
    self->maxlength = sizeof(self->buffer);
  self->filledto = 0;

  return self;
}

/*
=item free_gen_write_data(i_gen_write_data *info, int flush)

Cleans up the write buffer.

Will flush any left-over data if I<flush> is non-zero.

Returns non-zero if flush is zero or if info->cb() returns non-zero.

Return zero only if flush is non-zero and info->cb() returns zero.
ie. if it fails.

=cut
*/

int free_gen_write_data(i_gen_write_data *info, int flush)
{
  int result = !flush || 
    info->filledto == 0 ||
    info->cb(info->userdata, info->buffer, info->filledto);
  myfree(info);

  return result;
}

/*
=back

=head1 SEE ALSO

L<Imager>, L<gif.c>

=cut
*/