这个解决方案与Can BerkGüder的解决方案基本相同，但是花了一些时间写和发表评论后，我才觉得喜欢发布。
此功能创建的缩略图与您提供的尺寸完全一样。调整图像大小以使其最适合缩略图的大小。如果在两个方向上都不完全适合，则将其放在缩略图的中心。大量的评论解释了这一过程。
function thumbnail_box($img, $box_w, $box_h) { //create the image, of the required size $new = imagecreatetruecolor($box_w, $box_h); if($new === false) { //creation failed -- probably not enough memory return null; } //Fill the image with a light grey color //(this will be visible in the padding around the image, //if the aspect ratios of the image and the thumbnail do not match) //Replace this with any color you want, or comment it out for black. //I used grey for testing =) $fill = imagecolorallocate($new, 200, 200, 205); imagefill($new, 0, 0, $fill); //compute resize ratio $hratio = $box_h / imagesy($img); $wratio = $box_w / imagesx($img); $ratio = min($hratio, $wratio); //if the source is smaller than the thumbnail size, //don't resize -- add a margin instead //(that is, dont magnify images) if($ratio > 1.0) $ratio = 1.0; //compute sizes $sy = floor(imagesy($img) * $ratio); $sx = floor(imagesx($img) * $ratio); //compute margins //Using these margins centers the image in the thumbnail. //If you always want the image to the top left, //set both of these to 0 $m_y = floor(($box_h - $sy) / 2); $m_x = floor(($box_w - $sx) / 2); //Copy the image data, and resample // //If you want a fast and ugly thumbnail, //replace imagecopyresampled with imagecopyresized if(!imagecopyresampled($new, $img, $m_x, $m_y, //dest x, y (margins) 0, 0, //src x, y (0,0 means top left) $sx, $sy,//dest w, h (resample to this size (computed above) imagesx($img), imagesy($img)) //src w, h (the full size of the original) ) { //copy failed imagedestroy($new); return null; } //copy successful return $new;}用法示例：
$i = imagecreatefromjpeg("img.jpg");$thumb = thumbnail_box($i, 210, 150);imagedestroy($i);if(is_null($thumb)) { header('HTTP/1.1 500 Internal Server Error'); exit();}header('Content-Type: image/jpeg');imagejpeg($thumb);
