<?php
/*
 * This script demonstrates the mathematics of resizing an image to a different
 * width and height without stretching or squeezing the original image. If the
 * source image has a different aspect ratio than the destination image, the
 * source image will be cropped.
 * 
 * Consider a source image with a width of 320 pixels and a height of 240
 * pixels. The destination image is to be 80 pixels by 80 pixels. If these
 * dimensions were passed directly to imagecopyresampled(), the resized image
 * would appear to have a squeezed width. To prevent this, the width of the
 * source image should be cropped to 240 pixels so that the ratio of its width
 * to its height is 1:1, which is the same as the destination image's ratio.
 * When the source image is resized, it will not appear squeezed.
 */

$src = imagecreatefromjpeg('sample.jpg'); // Source image

$dw = 80;                    // Destination image Width
$dh = 80;                    // Destination image Height

$sw = imagesx($src);         // Source image Width
$sh = imagesy($src);         // Source image Height

$wr = $sw / $dw;             // Width Ratio (source:destination)
$hr = $sh / $dh;             // Height Ratio (source:destination)

$cx = 0;                     // Crop X (source offset left)
$cy = 0;                     // Crop Y (source offset top)

if ($hr < $wr)               // Height is the limiting dimension; adjust Width
{
    $ow = $sw;               // Old Source Width (temp)
    $sw = $dw * $hr;         // New virtual Source Width
    $cx = ($ow - $sw) / 2;   // Crops source width; focus remains centered
}
if ($wr < $hr)               // Width is the limiting dimension; adjust Height
{
    $oh = $sh;               // Old Source Height (temp)
    $sh = $dh * $wr;         // New virtual Source Height
    $cy = ($oh - $sh) / 2;   // Crops source height; focus remains centered
}
// If the width ratio equals the height ratio, the dimensions stay the same.

$dst = imagecreatetruecolor($dw, $dh); // Destination image
imagecopyresampled($dst, $src, 0, 0, $cx, $cy, $dw, $dh, $sw, $sh);

// Previews the resized image (not saved)
header('Content-type: image/jpeg');
imagejpeg($dst);
?>