Page 559 - Beginning PHP 5.3

Chapter 17: Generating Images with PHP

Opening an Existing Image
As you ’ ve already seen, to create a new image from scratch you use the imagecreate() or
imagecreatetruecolor() function. To create a new image based on an existing image, you use the
imagecreatefrom... series of functions. The most common of these are imagecreatefromjpeg() ,
imagecreatefromgif() , and imagecreatefrompng() . A number of other functions enable you to
create new images in memory from existing image formats, but they aren ’ t as widely used as these three.

The imagecreatefromjpeg() function works in the same way as the imagecreate() function, except
instead of passing it the width and height of the new image as parameters, you only pass the filename of
the existing image as a string. The function returns an image resource with which you can work.

For example, the line
$myImage = imagecreatefromjpeg( “lucky.jpg” );

opens the JPEG file called lucky.jpg that is in the same directory as the script, and stores its contents in
memory. The image resource identifier $myImage points to the image data in memory. You can test this
by outputting the image data to the browser.

Try It Out Display a JPEG

In this example you read an existing JPEG file into memory, then send it to the browser for displaying.
Save the following script as show_jpeg.php in your document root folder. Make sure that the
filename that you pass to the imagecreatefromjpeg() function is a JPEG file that exists in the same
folder.
<?php
$myImage = imagecreatefromjpeg( “lucky.jpg” );
header( “Content-type: image/jpeg” );
imagejpeg( $myImage );
imagedestroy( $myImage );
?>
Now open the script’s URL in your Web browser. Figure 17-16 shows a sample output — you’ll have a
different image, of course.

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