This algorithm is especially useful when you want to resize an image down to the maximum size possible inside a defined maximum width and maximum height, while maintaining the images dimensions.
The function accepts a php $_FILES array variable (as is created when an image is uploaded) image as a parameter. So if your HTML file form element was named “upload_image”, then you can pass $_FILES['upload_image'] to this function provided that the file was an image.
It will scale down the image passed to it based on the $MAX_HEIGHT and $MAX_WIDTH variables you can define at the top of the function (size in pixels).
The last part of the function creates a new image resource as the new scaled down version of the original image and returns it.
<?php
function make_thumb($image_resource)
{
$MAX_HEIGHT = 150; //pixels
$MAX_WIDTH = 100; //pixels
/*work out the new image dimensions*/
$imgsize = getimagesize($image_resource['tmp_name']);
$orig_height = $imgsize[1];
$orig_width = $imgsize[0];
$width_divider = $orig_width / $MAX_WIDTH;
$height_divider = $orig_height / $MAX_HEIGHT;
$temp_height = $orig_height / $width_divider;
$use_divider = $width_divider;
if($temp_height > $MAX_HEIGHT)
$use_divider = $height_divider;
$new_height = floor($orig_height / $use_divider);
$new_width = floor($orig_width / $use_divider);
/*create a new instance of the resized image*/
$new_image = imagecreatetruecolor($new_width, $new_height);
$old_img = imagecreatefromjpeg($image_resource['tmp_name']);
imagecopyresampled($new_image, $old_img,0,0,0,0, $new_width, $new_height, $orig_width, $orig_height);
return $new_image;
}
?>
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