XMM-Newton Science Analysis System


implot (implot-2.20.1) [22.0.0-9173c7d25-20250127]

Algorithm

The PGPLOT library routine PGIMAG is used to plot the image. The WCS library of Mark Calabretta is used to compute and plot the optional celestial coordinate grid (or tick-marks).

read parameters;

load the image;

find all null-valued pixels and set them to the minimum non-null image value;

if (--withzclip) {
  calculate the effective minimum and maximum image values effMin and effMax
  by histogram clipping;
} else {
  effMin = minval(image);
  effMax = maxval(image);
}

set up PGPLOT;

# Avoid irritating phenomenon in which background and foreground colours swap
# for ps/cps output, except within the image itself:
if (pgplot device is 'PS' or 'CPS') {
  if (labelcolour==0 || labelcolour==1) {
    labelcolour = 1 - labelcolour;
  }
  if (usercolours==0 || usercolours==1) {
    usercolours = 1 - usercolours;
  }
}

#...........................................................
# Plot the image:

calculate x and y pixel limits from --trimborder and --xfraclo etc;

call pgimag;

if (--withframe) {
  draw frame;

  write info at the side of the plot;

  draw colour wedge;

  if (--gridstyle eq 'none') {
    annotate frame with X and Y ticks;
  } else {
    annotate frame (using wcs keywords) with RA and DEC ticks;
  }
}

if (--gridstyle ne 'none') {
  draw RA/DEC grid;
}

if (withSrcList) {
#...........................................................
# Plot the sources:

  filter the source list using --expression;

  calculate source radii;

  if (--ncutsortstyle ne 'none') {
    sort the source list in order of the value of --ncutsortexpression;
  }

  truncate the sorted list at --ncut;

  calculate the source labels;

  foreach (remaining source) {
    calculate the image position of the source;

    plot the source circle;

    add the label;
  }

  if (--withframe) {
    write some stuff to the base and side of the plot;
  }
}