GD library provider

Very good start but I would like some more flexibility through the schema: the ability to set colors and vbar sizes programmatically, for example. Also, the vbar side is not very proficient in showing negative values, the grid always starts at 0 in your version.

I realise this comes in a bit late but I would really appreciate help in setting this up so that it can show negative values in a flexible manner. I've made some changes in gd_image_chart.inc but there's still some way to go as the starting point won't move; the grid does extend downwards but that doesn't comfort too much as the bounding box is in the wrong place. See attachment: test-negative-charting.png.

After nearly a year, I certainly didn't expect a response this quickly; thank you!

More to the point, I did introduce a min_value so that now the code in gd_image_chart_image looks like this:

  // layout
  // Added by kekkis
  $minval = 0;
  $maxval = 0;
  $nval = 0;
  $series_count = 0;
  foreach (element_children($data) as $series) {
    $series_data = _charts_series_values($data[$series]);
    $maxval = max($series_data) > $maxval ? max($series_data) : $maxval;
    // Added by kekkis
    $minval = min($series_data) < $minval ? min($series_data) : $minval;
    $nval = sizeof($series_data) > $nval ? sizeof($series_data) : $nval;
    $series_count +=1;
  }

And

// Changed by kekkis
//  $dydat = $maxval / $ngrid; // data units between grid lines
  $dydat = $maxval-$minval / $ngrid; // data units between grid lines
  $dypix = $ysize / ($ngrid + 1); // pixels between grid lines

// Changed by kekkis
//  for ($i = 0; $i <= ($ngrid + 1); $i++) {
  for ($i = floor($minval); $i <= ($ngrid + 1); $i++) {

But this results in what I attached above; the 0 line is still at the bottom. Any pointers as to how that could be moved up dynamically as needed would be nice. The data in the attachment is [-4.8, -22.8] and it is not reflected very nicely.

Mads,

hoy!! after staying away from Drupal so long, i see a quite nice implementation! thanks a lot. Users might now use Charts (line and bars at least) almost without external libs (since gd is de facto standard library)!

commited and soon on the next release.

regards,

massa

PS: would you like to be a co-maintainer?

Wondering if this plugin is being moved to Drupal 7 and 8? I have a real need for it. If anyone has done so, please let me know, or if there are any interest in co-developing I am available.

Regards

> Wondering if this plugin is being moved to Drupal 7 and 8?

This module was ported months ago to Drupal 7, but it does not include a GD-based charting library (nor will it, more likely than not). The issue for D8 porting the entire module is at #2140651: Port Charts to Drupal 8.

For the GD-version of a charting library, I'd suggest an add-on module that stands alone, similar to https://drupal.org/project/charts_rgraph. I wouldn't want to maintain a custom charting solution as part of this project.

Thanks @quicksketch - it makes total sense that this should be a plugin, just like any other output option. IMO this is a huge need, though, because once one moves beyond "small data", nevermind "big data", client-side javascript based solutions are a performance killer.

I'm interested in getting more info about what's in comment #10. Also, would the SVG Graph library be a possible alternative to consider as a remedy? That library is open source, written in PHP, and used in forena.

PS: what exactly is the "GD library"? Any link for more details on it?