Ask Owen » PHP http://askowen.info Your friendly neighbourhood geek Mon, 06 Feb 2012 22:14:38 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 How can I upload an automatically resize an image on my website? http://askowen.info/2008/06/how-can-i-upload-an-automatically-resize-an-image-on-my-website/ http://askowen.info/2008/06/how-can-i-upload-an-automatically-resize-an-image-on-my-website/#comments Tue, 10 Jun 2008 13:59:18 +0000 Owen http://askowen.info/?p=186

I often need to upload images to my website, but I’d like them to be automatically resized when they’re uploaded. How can I do this??


I got this question from from a colleague of mine who was answering some questions for a client. His client’s requirements were a bit more complex than just this question, but I thought this would be a good one to put up on AskOwen and use it as a tutorial for some interesting PHP techniques. Here’s some PHP code that will accomplish the request:


<?php
// Image uploaded and resizer
// from http://AskOwen.info
?>
<html>
<head>
<title>Image Uploader and Resizer</title>
</head>
<body>
<?php
if (array_key_exists('btn', $_POST)) {
$uploadedfile = $_FILES['uploadfile']['tmp_name'];
$src = imagecreatefromjpeg($uploadedfile);
list($width,$height)=getimagesize($uploadedfile);
$newwidth=600;
$newheight=($height/$width)*600;
$tmp=imagecreatetruecolor($newwidth,$newheight);
imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);
$filename = "images/". $_FILES['uploadfile']['name'];
imagejpeg($tmp,$filename,100);
imagedestroy($src);
imagedestroy($tmp);
}
?>
<form action="upload.php" method="post" enctype="multipart/form-data" >
<input type="file" name="uploadfile"/>
<input id="btn" name="btn" type="submit"/>
</body>

Here’s a quick run through the algorithm:

  1. Pick up the file that has been uploaded by the form
  2. Get the images width and height
  3. Calculate the correct height to maintain the aspect ratio of the image
  4. Create a memory space for the new image
  5. Use imagecopyresampled, a PHP function that resizes the image for you, to generate the new image
  6. Write the file to disk
  7. Clean up memory space

It’s quite straight forward once you know that PHP has the graphical functions you need to accomplish this.  It’s worth nothing that there’s another PHP function that can resize an image for you also, called imagecopyresized, however this function only uses 255 colours to generate the target image and so doesn’t maintain the fidelity of the image so well. This may be fine if you have some line art you’re converting, but if you wanted to resize that beautiful photo you took last time you went on holiday and stayed at one of the Hilton Head rentals you hear so much about, well, you really want as clear an image as possible.

As I said above, this is just the bare bones of an image resizing script, but it illustrates some of the graphical functions that PHP has available (through the GD library) that can help you produce some really useful scripts.

]]> http://askowen.info/2008/06/how-can-i-upload-an-automatically-resize-an-image-on-my-website/feed/ 0 How can I generate images with PHP? http://askowen.info/2008/03/how-can-i-generate-images-with-php/ http://askowen.info/2008/03/how-can-i-generate-images-with-php/#comments Tue, 04 Mar 2008 10:24:29 +0000 Owen http://askowen.info/?p=84

I’d like to have an image on my website that gets updated with different text based on the current user. My website is built in PHP. Can I do this?


I got a question from a friend who works for a web development company and was building a website for an insurance firm. He was preparing a page that showed off car insurance and wanted to have an image with a dynamically generated value on it showing different savings based on user input.

Producing an image with PHP isn’t all that hard. Here’s some sample code that we’ll use as reference:
< ?php
header("Content-type: image/png");
$print_value = "Save 15%"; // this can be changed as needed
$img = imagecreatefrompng("backdrop.png");
$orange = imagecolorallocate($img, 220, 210, 60);
$new_pic = (imagesx($img) - 7.5 * strlen($print_value)) / 2;
imagestring($img, 3, $new_pic, 9, $print_value, $orange);
imagepng($img);
imagedestroy($img);
?>

That’s not too many lines of code, is it? And calling it is just as easy. Let’s say the code above is saved in a file called make_image.php. All you have to do is add the tag <img src=”make_image.php”/> to your HTML code, and you’re done!

Here’s a quick explanation of what the code does. The first line sets your HTTP header so that a browser will interpret the data coming from the PHP file as an image (.PNG to be exact). It then proceeds to build the image based on a background image and some text that is specified in the code. This is then output to the browser and memory used for the image cleared at the end of the process. It’s quite easy to adapt this to your needs once you understand what the code is doing.

Hope this helps!

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