php-gtk2 Cookbook: How to draw a simple bar graph using GD2?

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Sample Code 232: How to draw a simple bar graph using GD2?

Written by kksou

Monday, 14 May 2007

Problem

You would like to draw a simple bar graph from a set of data as shown below:

How to draw a simple bar graph using GD2?

Solution

We can draw a simple bar graph using the GD2 library. For those of you who are not familiar with GD2, please refer to the PHP documentation at: http://www.php.net/gd

To run the following example, make sure you php-gtk2 is compiled with GD2 library.

Note: The Gnope Installer version DOES NOT support GD2. Please download the latest php-gtk2 binary from the official PHP-GTK site as outlined in the article How to install php gtk2 on windows?

Sample Code

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<?php
$window = new GtkWindow();
$window->set_title($argv[0]);
$window->connect_simple('destroy', array('Gtk','main_quit'));
$window->add($vbox = new GtkVBox());

// display title
$title = new GtkLabel("Draw a simple Bar Graph");
$title->modify_font(new PangoFontDescription("Times New Roman Italic 10"));
$title->modify_fg(Gtk::STATE_NORMAL, GdkColor::parse("#0000ff"));
$title->set_size_request(-1, 40);
$title->set_justify(Gtk::JUSTIFY_CENTER);
$alignment = new GtkAlignment(0.5, 0, 0, 0);
$alignment->add($title);
$vbox->pack_start($alignment, 0, 0);
$vbox->pack_start(new GtkLabel(), 0, 0);

draw_bargraph($vbox); // note 1

$window->show_all();
Gtk::main();

function draw_bargraph($vbox) {
    $data = array('120','160','300','240');
    $im = imagecreate(360, 200);

    $white = imagecolorallocate($im,255,255,255);
    $black = imagecolorallocate($im,0,0,0);
    $blue = imagecolorallocate($im,0,0,255);
    //
    // create background box
    //imagerectangle($im, 1, 1, 319, 239, $black);
    //draw X, Y Co-Ordinate
    imageline($im, 10, 5, 10, 180, $black );
    imageline($im, 10, 180, 340, 180, $black );
    imagestring($im,6,100,25,"Simple Bar Graph", $black);

    // what next draw the bars
    $x = 30;
    $y = 180;
    $w = 40;
    // get into some meat now, cheese for vegetarians;
    for ($i=0;$i<count($data);$i++){

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Explanation

Draw the bar graph using GD2.
Load the graph into GdkPixbuf.
Create a new GtkImage from the pixbuf.
Resize the GtkImage so that the entire bar graph is displayed.