Advanced Graphics Manipulation - Page 17

Now that we understand the basics of image functions and how we can apply them, let's take a look at some of the more advanced functions, the concepts behind them and their application.

A Stylized Map

For this example we're going to dynamically create a stylized map. The map of the area itself will already exist and we will use this as a starting point. We shall then create a series of separate images, each containing an icon that represents an attraction on our map. We can then combine the images to create a composite map, with icons highlighting any of the tourist attractions.

The code that we use in this example will not be database driven, but will have the coordinates hard-coded into the script. You can easily combine the techniques we use here with the techniques we covered in the previous example if you wish to make a dynamic version of this map.

Here's the map that we'll be dropping our icons onto:
On top of this image we want to draw what appears to be a pin stuck into the map:
We'll call these files island.jpg and pin.jpg respectively.

Copies of these files are included in the code download for this book, available from http://www.wrox.com. Alternatively, you can use your own images and modify the following code accordingly.

We simply open up both of our image files and use ImageCopyResized() to copy the pin into the map image, and place it where we want:

<?php
//map.php
Header("Content-type: image/jpeg");
$image = ImageCreateFromJPEG("island.jpg");
$icon = ImageCreateFromJPEG("pin.jpg");
$width = ImageSX($icon);
$height = ImageSY($icon);
ImageCopyResized($image,$icon,174,200,
	0,0,$width,$height,$width,$height);
ImageJPEG($image);
ImageDestroy($image);
?>

Note that we use three JPEG-specific functions here that are completely equivalent to the corresponding PNG functions we've used above. Only the names have been changed.

	Two more functions that we haven't seen before, ImageSX() and ImageSY() return the width and height of the specified image respectively. We then use these values as width and height values for source and destination images in ImageCopyResized().
	You'll notice straight away that there's a problem with the figure, as shown on the left. The white background of our pin image has been copied through as well as the pin itself, and has obscured part of the map.

Modifying the Script - Page 16
Beginning PHP4
The ImageColorTransparent() Function - Page 18