function chart(&$log_data, $chan, $filename)
{
$w = 1800;
$h = 800;
$nick_data = array();
for ($i = 0; $i < count($log_data); $i++) {
if ($log_data[$i]["dest"] != $chan) {
continue;
}
$nick = $log_data[$i]["nick"];
$nick_data[$nick][] = $log_data[$i];
}
$left_margin = 50;
# pixels
$min_y = -1;
$max_y = count($nick_data) - 1;
$min_x = $log_data[0]["timestamp"];
$max_x = $log_data[count($log_data) - 1]["timestamp"];
$dx = $max_x - $min_x;
term_echo("*** dx = {$dx}");
$dt = 1 / chart__ppu($w - $left_margin, $min_x, $max_x);
# number of seconds per pixel
term_echo("*** dt = {$dt}");
$m = $dx / $dt;
term_echo("*** m = {$m}");
$chart_data = array();
$y = 0;
$max_lines_per_pixel = 0;
foreach ($nick_data as $nick => $records) {
for ($i = 0; $i < count($nick_data[$nick]); $i++) {
$x = chart__r2p_x($w, $min_x, $max_x, $log_data[$i]["timestamp"]) + $left_margin;
if (isset($chart_data[$nick][$x]) == True) {
$chart_data[$nick][$x] = $chart_data[$nick][$x] + 1;
} else {
$chart_data[$nick][$x] = 1;
}
$max_lines_per_pixel = max($max_lines_per_pixel, $chart_data[$nick][$x]);
}
}
$dl = $max_lines_per_pixel / 255;
# number of lines per color gradient (decimal)
# paint chart
$buffer = imagecreatetruecolor($w, $h);
$color_bg = imagecolorallocate($buffer, 255, 255, 255);
imagefill($buffer, 0, 0, $color_bg);
$y = 0;
foreach ($chart_data as $nick => $data) {
$y++;
$py1 = chart__r2p_y($h, $min_y, $max_y, $y) + round(0.3 * chart__ppu($h, $min_y, $max_y));
$py2 = chart__r2p_y($h, $min_y, $max_y, $y) - round(0.3 * chart__ppu($h, $min_y, $max_y));
foreach ($chart_data[$nick] as $px => $intensity) {
$color_x = imagecolorallocate($buffer, 0, 0, round($dl * $intensity));
imageline($buffer, $px, $py1, $px, $py2, $color_x);
}
}
#scale_img($buffer,0.5,$w,$h);
imagepng($buffer, $filename . ".png");
imagedestroy($buffer);
}
function chart__p2r_y($h, $min_y, $max_y, $py)
{
return ($h - 1 - $py) / chart__ppu($h, $min_y, $max_y) + $min_y;
}
