convert.im

/*
=head1 NAME

  convert.im - image conversions

=head1 SYNOPSIS

  out = i_convert(srcimage, coeff, outchans, inchans)

=head1 DESCRIPTION

Converts images from one format to another, typically in this case for
converting from RGBA to greyscale and back.

=over

=cut
*/

#define IMAGER_NO_CONTEXT
#include "imager.h"

struct chan_copy {
  /* channels to copy */
  int copy_count;
  int from[MAXCHANNELS];
  int to[MAXCHANNELS];

  /* channels to zero */
  int zero_count;
  int zero[MAXCHANNELS];

  /* channels to set to maxsample */
  int one_count;
  int one[MAXCHANNELS];
};

static int 
is_channel_copy(i_img *im, const double *coeff, 
		int outchan, int inchan, 
		struct chan_copy *info);

static i_img *
convert_via_copy(i_img *im, i_img *src, struct chan_copy *info);

/*
=item i_convert(src, coeff, outchan, inchan)

Converts the image src into another image.

coeff contains the co-efficients of an outchan x inchan matrix, for
each output pixel:

              coeff[0], coeff[1] ...
  im[x,y] = [ coeff[inchan], coeff[inchan+1]...        ] * [ src[x,y], 1]
              ...              coeff[inchan*outchan-1]

If im has the wrong number of channels or is the wrong size then
i_convert() will re-create it.

Now handles images with more than 8-bits/sample.

=cut
*/

i_img *
i_convert(i_img *src, const double *coeff, int outchan, int inchan) {
  double work[MAXCHANNELS];
  i_img_dim x, y;
  int i, j;
  int ilimit;
  i_img *im = NULL;
  dIMCTXim(src);

  im_log((aIMCTX,1,"i_convert(im %p, src %p, coeff %p,outchan %d, inchan %d)\n",
	  im, src, coeff, outchan, inchan));
 
  im_clear_error(aIMCTX);

  ilimit = inchan;
  if (ilimit > src->channels)
    ilimit = src->channels;
  if (outchan > MAXCHANNELS) {
    im_push_error(aIMCTX, 0, "cannot have outchan > MAXCHANNELS");
    return 0;
  }

  if (src->type == i_direct_type) {
    struct chan_copy info;
    im = i_sametype_chans(src, src->xsize, src->ysize, outchan);
    
    if (is_channel_copy(src, coeff, outchan, inchan, &info)) {
      return convert_via_copy(im, src, &info);
    }
    else {
#code src->bits <= i_8_bits
      IM_COLOR *vals;
      
      /* we can always allocate a single scanline of i_color */
      vals = mymalloc(sizeof(IM_COLOR) * src->xsize); /* checked 04Jul05 tonyc */
      for (y = 0; y < src->ysize; ++y) {
	IM_GLIN(src, 0, src->xsize, y, vals);
	for (x = 0; x < src->xsize; ++x) {
	  for (j = 0; j < outchan; ++j) {
	    work[j] = 0;
	    for (i = 0; i < ilimit; ++i) {
	      work[j] += coeff[i+inchan*j] * vals[x].channel[i];
	    }
	    if (i < inchan) {
	      work[j] += coeff[i+inchan*j] * IM_SAMPLE_MAX;
	    }
	  }
	  for (j = 0; j < outchan; ++j) {
	    if (work[j] < 0)
	      vals[x].channel[j] = 0;
	    else if (work[j] >= IM_SAMPLE_MAX)
	      vals[x].channel[j] = IM_SAMPLE_MAX;
	    else
	      vals[x].channel[j] = work[j];
	  }
	}
	IM_PLIN(im, 0, src->xsize, y, vals);
      }
      myfree(vals);
#/code
    }
  }
  else {
    int count;
    int outcount;
    int index;
    i_color *colors;
    i_palidx *vals;

    im = im_img_pal_new(aIMCTX, src->xsize, src->ysize, outchan, 
			i_maxcolors(src));

    /* just translate the color table */
    count = i_colorcount(src);
    outcount = i_colorcount(im);
    /* color table allocated for image, so it must fit */
    colors = mymalloc(count * sizeof(i_color)); /* check 04Jul05 tonyc */
    i_getcolors(src, 0, colors, count);
    for (index = 0; index < count; ++index) {
      for (j = 0; j < outchan; ++j) {
        work[j] = 0;
        for (i = 0; i < ilimit; ++i) {
          work[j] += coeff[i+inchan*j] * colors[index].channel[i];
        }
        if (i < inchan) {
          work[j] += coeff[i+inchan*j] * 255.9;
        }
      }
      for (j = 0; j < outchan; ++j) {
        if (work[j] < 0)
          colors[index].channel[j] = 0;
        else if (work[j] >= 255)
          colors[index].channel[j] = 255;
        else
          colors[index].channel[j] = work[j];
      }
    }
    if (count < outcount) {
      i_setcolors(im, 0, colors, count);
    }
    else {
      i_setcolors(im, 0, colors, outcount);
      i_addcolors(im, colors, count-outcount);
    }
    /* and copy the indicies */
    /* i_palidx is always unsigned char and will never be bigger than short
       and since a line of 4-byte i_colors can fit then a line of i_palidx
       will fit */
    vals = mymalloc(sizeof(i_palidx) * im->xsize); /* checked 4jul05 tonyc */
    for (y = 0; y < im->ysize; ++y) {
      i_gpal(src, 0, im->xsize, y, vals);
      i_ppal(im, 0, im->xsize, y, vals);
    }
    myfree(vals);
    myfree(colors);
  }

  return im;
}

/*
=item is_channel_copy(coeff, outchan, inchan, chan_copy_info)

Test if the coefficients represent just copying channels around, and
initialize lists of the channels to copy, zero or set to max.

=cut
*/

static
int is_channel_copy(i_img *im, const double *coeff, int outchan, int inchan, 
		    struct chan_copy *info) {
  int srcchan[MAXCHANNELS];
  int onechan[MAXCHANNELS];
  int i, j;
  int ilimit = im->channels > inchan ? inchan : im->channels;

  for (j = 0; j < outchan; ++j) {
    srcchan[j] = -1;
    onechan[j] = 0;
  }

  for (j = 0; j < outchan; ++j) {
    for (i = 0; i < ilimit; ++i) {
      if (coeff[i+inchan*j] == 1.0) {
	if (srcchan[j] != -1) {
	  /* from two or more channels, not a copy */
	  return 0;
	}
	srcchan[j] = i;
      }
      else if (coeff[i+inchan*j]) {
	/* some other non-zero value, not a copy */
	return 0;
      }
    }
    if (i < inchan) {
      if (coeff[i+inchan*j] == 1.0) {
	if (srcchan[j] != -1) {
	  /* can't do both */
	  return 0;
	}
	onechan[j] = 1;
      }
      else if (coeff[i+inchan*j]) {
	/* some other non-zero value, not a copy */
	return 0;
      }
    }
  }

  /* build our working data structures */
  info->copy_count = info->zero_count = info->one_count = 0;
  for (j = 0; j < outchan; ++j) {
    if (srcchan[j] != -1) {
      info->from[info->copy_count] = srcchan[j];
      info->to[info->copy_count] = j;
      ++info->copy_count;
    }
    else if (onechan[j]) {
      info->one[info->one_count] = j;
      ++info->one_count;
    }
    else {
      info->zero[info->zero_count] = j;
      ++info->zero_count;
    }
  }

#if 0
  {
    for (i = 0; i < info->copy_count; ++i) {
      printf("From %d to %d\n", info->from[i], info->to[i]);
    }
    for (i = 0; i < info->one_count; ++i) {
      printf("One %d\n", info->one[i]);
    }
    for (i = 0; i < info->zero_count; ++i) {
      printf("Zero %d\n", info->zero[i]);
    }
    fflush(stdout);
  }
#endif

  return 1;
}

/*
=item convert_via_copy(im, src, chan_copy_info)

Perform a convert that only requires channel copies.

=cut
*/

static i_img *
convert_via_copy(i_img *im, i_img *src, struct chan_copy *info) {
#code src->bits <= i_8_bits
  IM_COLOR *in_line = mymalloc(sizeof(IM_COLOR) * src->xsize);
  IM_COLOR *out_line = mymalloc(sizeof(IM_COLOR) * src->xsize);
  i_img_dim x, y;
  int i;
  IM_COLOR *inp, *outp;

  for (y = 0; y < src->ysize; ++y) {
    IM_GLIN(src, 0, src->xsize, y, in_line);

    inp = in_line;
    outp = out_line;
    for (x = 0; x < src->xsize; ++x) {
      for (i = 0; i < info->copy_count; ++i) {
	outp->channel[info->to[i]] = inp->channel[info->from[i]];
      }
      for (i = 0; i < info->one_count; ++i) {
	outp->channel[info->one[i]] = IM_SAMPLE_MAX;
      }
      for (i = 0; i < info->zero_count; ++i) {
	outp->channel[info->zero[i]] = 0;
      }
      ++inp;
      ++outp;
    }
    
    IM_PLIN(im, 0, src->xsize, y, out_line);
  }
  
  myfree(in_line);
  myfree(out_line);
#/code
      
  return im;
}

/*
=back

=head1 SEE ALSO

Imager(3)

=head1 AUTHOR

Tony Cook <tony@develop-help.com>

=cut
*/