Online Thumbnail Creator using GD function :
The first step in our online thumbnail creator is to create a form, and make it possible to upload an image. See the example below:
<?php
if ($_POST) {
// No image?
if (empty($_FILES[’image’]) OR $_FILES[’image’][’error’] != UPLOAD_ERR_OK) {
die (’<strong>Invalid image uploaded. Please go back and try again.</strong>’);
}
$imagepath = $_FILES[’image’][’tmp_name’];
// Load image
$image = open_image($imagepath);
if ($image == false) {
die (’<strong>You uploaded an invalid image. Please go back and try again.</strong>’);
}
// TODO: resizing the image
}
// Display the upload form:
?>
<html>
<head>
<title>Image Resizer</title>
<style type=”text/css”>
th { text-align: right; }
</style>
</head>
<body>
<form method=”POST” enctype=”multipart/form-data”>
<table>
<tr>
<th>Image:</th>
<td><input type=”file” name=”image”></td>
</tr>
<tr>
<th>Resize by: </th>
<td><input type=”text” name=”percent” size=”1″ />% (percentage)</td>
</tr>
<tr>
<th>OR new width: </th>
<td><input type=”text” name=”new_width” size=”1″ /> pixels (height will be calculated automatically)</td>
</tr>
<tr>
<th>OR new height: </th>
<td><input type=”text” name=”new_height” size=”1″ /> pixels (width will be calculated automatically)</td>
</tr>
<tr>
<th>OR new height and new width: </th>
<td>
<table>
<tr><td>width:</td><td><input type=”text” name=”width” size=”1″ /> pixels</td></tr>
<tr><td>height:</td><td><input type=”text” name=”height” size=”1″ /> pixels</td></tr>
</table>
</td>
</tr>
<tr><td colspan=”2″ style=”text-align:center;”><input type=”submit” value=”Resize Image” /></td></tr>
</form>
</body>
</html>
Now that we have a form to upload the image and are able to specify how we want to resize it, we will have to write the actual code for resizing.
// Percentage?
if (!empty($_POST[’percent’]) AND is_numeric($_POST[’percent’])) {
$percent = floatval($_POST[’percent’]);
$percent = $percent/100;
$new_width = $width * $percent;
$new_height = $height * $percent;
// New width? Calculate new height
} elseif (!empty($_POST[’new_width’]) AND is_numeric($_POST[’new_width’])) {
$new_width = floatval($_POST[’new_width’]);
$new_height = $height * ($new_width/$width);
// New height? Calculate new width
} elseif (!empty($_POST[’new_height’]) AND is_numeric($_POST[’new_height’])) {
$new_height = floatval($_POST[’new_height’]);
$new_width = $width * ($new_height/$height);
// New height and new width
} elseif (!empty($_POST[’height’]) AND is_numeric($_POST[’height’]) AND !empty($_POST[’width’]) AND is_numeric($_POST[’width’])) {
$new_height = floatval($_POST[’height’]);
$new_width = floatval($_POST[’width’]);
} else {
die (’<strong>You didn\’t specify any resizing options.</strong>’);
}
In above example, we use a simple if-then-else structure to check all the resizing options.
All that’s left to do is resize the image, and then display it, using the following standard code:
// Resample
$image_resized = imagecreatetruecolor($new_width, $new_height);
imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
// Display resized image
header(’Content-type: image/jpeg’);
imagejpeg($image_resized);
die();
We’ve now got a fully functional online image resizer, which can be used to resize almost any kind of image.
