Recipe 17.6. Building Dynamic Images


17.6.2. Problem

You want to create an image based on an existing image template and dynamic data (typically text). For instance, you want to create a hit counter.

17.6.3. Solution

Load the template image, find the correct position to properly center your text, add the text to the canvas, and send the image to the browser:

// Configuration settings $image    = ImageCreateFromPNG('button.png'); $text     = $_GET['text']; $font     = ImagePSLoadFont('Times'); $size     = 24; $color    = ImageColorAllocate($image,   0,   0,   0); // black $bg_color = ImageColorAllocate($image, 255, 255, 255); // white // Print-centered text list($x, $y) = pc_ImagePSCenter($image, $text, $font, $size); ImagePSText($image, $text, $font, $size, $color, $bg_color, $x, $y); // Send image header('Content-type: image/png'); ImagePNG($image); // Clean up ImagePSFreeFont($font); ImageDestroy($image);

17.6.4. Discussion

Building dynamic images with GD is easy; all you need to do is combine a few recipes together. At the top of the code in the Solution, you load in an image from a stock template button; it acts as the background on which you overlay the text. We define the text to come directly from the query string. Alternatively, you can pull the string from a database (in the case of access counters) or a remote server (stock quotes or weather report icons).

After that, continue with the other settings: loading a font and specifying its size, color, and background color. Before printing the text, however, you need to compute its position; pc_ImagePSCenter( ) from Recipe 17.5 nicely solves this task. Last, serve the image, and deallocate the font and image from memory.

For example, the following code generates a page of HTML and image tags using dynamic buttons, as shown in Figure 17-9:

<?php if (isset($_GET['button'])) {     // Configuration settings     $image    = ImageCreateFromPNG('button.png');     $text     = $_GET['button'];      // dynamically generated text     $font     = ImagePSLoadFont('Times');     $size     = 24;     $color    = ImageColorAllocate($image,   0,   0,   0); // black     $bg_color = ImageColorAllocate($image, 255, 255, 255); // white     // Print centered text     list($x, $y) = pc_ImagePSCenter($image, $text, $font, $size);     ImagePSText($image, $text, $font, $size, $color, $bg_color, $x, $y);     // Send image     header('Content-type: image/png');     ImagePNG($image);     // Clean up     ImagePSFreeFont($font);     ImageDestroy($image);     $url = htmlentities($_SERVER['PHP_SELF']); } else { ?> <html> <head>     <title>Sample Button Page</title> </head> <body>     <img src="/books/3/131/1/html/2/<?php echo $url; ?>?button=Previous"          alt="Previous" width="132" height="46">     <img src="/books/3/131/1/html/2/<?php echo $url; ?>?button=Next"          alt="Next"     width="132" height="46"> </body> </html> <?php } ?>

Sample button page


In this script, if a value is passed in for $_GET['button'], you generate a button and send out the PNG. If $_GET['button'] isn't set, you print a basic HTML page with two embedded calls back to the script with requests for button images one for a Previous button and one for a Next button. A more general solution is to create a separate button.php page that returns only graphics and set the image source to point at that page.

17.6.5. See Also

Recipe 17.4 for more on drawing text; Recipe 17.5 for more on centering text; Chapter 9, "Graphics," in Programming PHP, Second Edition, by Rasmus Lerdorf, Kevin Tatroe, and Peter MacIntyre (O'Reilly).




PHP Cookbook, 2nd Edition
PHP Cookbook: Solutions and Examples for PHP Programmers
ISBN: 0596101015
EAN: 2147483647
Year: 2006
Pages: 445

Similar book on Amazon

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net