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thummer.php
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thummer.php
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<?php
class Thummer {
const MIN_LENGTH = 50;
const MAX_LENGTH = 500;
const BASE_SOURCE_DIR = '/webapp/docroot/content/image';
const BASE_TARGET_DIR = '/webapp/docroot/content/imagethumb';
const REQUEST_PREFIX_URL_PATH = '/content/imagethumb';
const SHARPEN_THUMBNAIL = true;
const JPEG_IMAGE_QUALITY = 75;
const PNG_SAVE_TRANSPARENCY = false;
const HTTP_THUMBNAIL_RESPONSE = false;
const FAIL_IMAGE_URL_PATH = '/content/thumbfail.jpg';
const FAIL_IMAGE_LOG = false;
public function __construct() {
// get requested thumbnail from URI
$requestURI = trim($_SERVER['REQUEST_URI']);
$requestedThumb = $this->getRequestedThumb($requestURI);
if ($requestedThumb === false) {
// unable to determine requested thumbnail from URL
$this->send404header();
return;
}
// fetch source image details
$sourceImageDetail = $this->getSourceImageDetail($requestedThumb[2]);
if ($sourceImageDetail === false) {
// unable to locate source image
$this->send404header();
return;
}
if ($sourceImageDetail === -1) {
// source image invalid - redirect to fail image
$this->redirectURL(self::FAIL_IMAGE_URL_PATH);
$this->logFailImage($requestedThumb[2]);
return;
}
// source image all good, create thumbnail on disk
$targetImagePathFull = $this->generateThumbnail($requestedThumb,$sourceImageDetail);
if (self::HTTP_THUMBNAIL_RESPONSE) {
// output the generated thumbnail binary to the client
if (is_file($targetImagePathFull)) {
header('Content-Length: ' . filesize($targetImagePathFull));
header('Content-Type: ' . $sourceImageDetail[3]);
readfile($targetImagePathFull);
}
} else {
// redirect back to initial URL to display generated thumbnail image
$this->redirectURL($requestURI);
}
}
private function getRequestedThumb($requestPath) {
// check for URL prefix - remove if found
$requestPath = (strpos($requestPath,self::REQUEST_PREFIX_URL_PATH) === 0)
? substr($requestPath,strlen(self::REQUEST_PREFIX_URL_PATH))
: $requestPath;
// extract target thumbnail dimensions & source image
if (!preg_match(
'{^/([0-9]{1,4})x([0-9]{1,4})(/.+)$}',
$requestPath,$requestMatch
)) return false;
// ensure width/height are within allowed bounds
$width = intval($requestMatch[1]);
$height = intval($requestMatch[2]);
if (($width < self::MIN_LENGTH) || ($width > self::MAX_LENGTH)) return false;
if (($height < self::MIN_LENGTH) || ($height > self::MAX_LENGTH)) return false;
return array(
$width,$height,
// remove parent path components if request is trying to be sneaky
str_replace(
array('../','./'),'',
$requestMatch[3]
)
);
}
private function getSourceImageDetail($source) {
// image file exists?
$srcPath = self::BASE_SOURCE_DIR . $source;
if (!is_file($srcPath)) return false;
// valid web image? return width/height/type
set_error_handler(array($this,'errorWarningSink'));
$detail = getimagesize($srcPath);
restore_error_handler();
if (
($detail !== false) &&
(($detail[2] == IMAGETYPE_GIF) || ($detail[2] == IMAGETYPE_JPEG) || ($detail[2] == IMAGETYPE_PNG))
) return array(
$detail[0],$detail[1], // width/height
$detail[2], // image type
$detail['mime'] // MIME type
);
// not a valid image(type)
return -1;
}
private function generateThumbnail(array $requestedThumb,array $sourceImageDetail) {
// calculate source image copy dimensions, fixed to target requested thumbnail aspect ratio
list($targetWidth,$targetHeight,$targetImagePathSuffix) = $requestedThumb;
list($sourceWidth,$sourceHeight,$sourceType) = $sourceImageDetail;
$targetAspectRatio = $targetWidth / $targetHeight;
$copyWidth = intval($sourceHeight * $targetAspectRatio);
$copyHeight = $sourceHeight;
if ($copyWidth > $sourceWidth) {
// resize copy height fixed to target aspect
$copyWidth = $sourceWidth;
$copyHeight = intval($sourceWidth / $targetAspectRatio);
}
// create source/target GD images and resize/resample
$imageSrc = $this->createSourceGDImage($sourceType,self::BASE_SOURCE_DIR . $targetImagePathSuffix);
$imageDst = imagecreatetruecolor($targetWidth,$targetHeight);
if (($sourceType == IMAGETYPE_PNG) && self::PNG_SAVE_TRANSPARENCY) {
// save PNG transparency in target thumbnail
imagealphablending($imageDst,false);
imagesavealpha($imageDst,true);
}
imagecopyresampled(
$imageDst,$imageSrc,0,0,
$this->calcThumbnailSourceCopyPoint($sourceWidth,$copyWidth),$this->calcThumbnailSourceCopyPoint($sourceHeight,$copyHeight),
$targetWidth,$targetHeight,
$copyWidth,$copyHeight
);
// sharpen thumbnail
$this->sharpenThumbnail($imageDst);
// construct full path to target image on disk and temp filename
$targetImagePathFull = sprintf('%s/%dx%d%s',self::BASE_TARGET_DIR,$targetWidth,$targetHeight,$targetImagePathSuffix);
$targetImagePathFullTemp = $targetImagePathFull . '.' . md5(uniqid());
// if target image path doesn't exist, create it now
if (!is_dir(dirname($targetImagePathFull))) {
// setting a custom error handler to catch a possible warning if the directory already exists
// this will happen if two PHP requests decide to create the new directory at the same time (race condition)
set_error_handler(array($this,'errorWarningSink'));
mkdir(dirname($targetImagePathFull),0777,true);
restore_error_handler();
}
// save image to temp file
switch ($sourceType) {
case IMAGETYPE_GIF:
imagegif($imageDst,$targetImagePathFullTemp);
break;
case IMAGETYPE_JPEG:
imagejpeg($imageDst,$targetImagePathFullTemp,self::JPEG_IMAGE_QUALITY);
break;
default: // PNG image
imagepng($imageDst,$targetImagePathFullTemp);
}
// destroy GD image instances
imagedestroy($imageSrc);
imagedestroy($imageDst);
// move temp image file into place, avoiding race conditions between thummer requests and set modify timestamp to source image
rename($targetImagePathFullTemp,$targetImagePathFull);
touch($targetImagePathFull,filemtime(self::BASE_SOURCE_DIR . $targetImagePathSuffix));
return $targetImagePathFull;
}
private function createSourceGDImage($type,$path) {
if ($type == IMAGETYPE_GIF) return imagecreatefromgif($path);
if ($type == IMAGETYPE_JPEG) return imagecreatefromjpeg($path);
return imagecreatefrompng($path);
}
private function calcThumbnailSourceCopyPoint($sourceLength,$copyLength) {
$point = intval(($sourceLength - $copyLength) / 2);
return max($point,0);
}
private function sharpenThumbnail($image) {
if (!self::SHARPEN_THUMBNAIL) return;
// build matrix and divisor
$matrix = array(
array(-1.2,-1,-1.2),
array(-1,20,-1),
array(-1.2,-1,-1.2)
);
// apply to image
imageconvolution(
$image,$matrix,
11.2,0 // note: array_sum(array_map('array_sum',$matrix)) = 11.2;
);
}
private function errorWarningSink() {
// sink it
}
private function logFailImage($source) {
if (self::FAIL_IMAGE_LOG === false) return;
// write the requested file path to the error log
$fp = fopen(self::FAIL_IMAGE_LOG,'a');
fwrite($fp,self::BASE_SOURCE_DIR . $source . "\n");
fclose($fp);
}
private function send404header() {
header('HTTP/1.0 404 Not Found');
}
private function redirectURL($targetPath) {
header(
sprintf(
'Location: http%s://%s%s',
((isset($_SERVER['SERVER_PORT'])) && ($_SERVER['SERVER_PORT'] == 443)) ? 's' : '',
$_SERVER['HTTP_HOST'],
$targetPath
),
true,301
);
}
}
new Thummer();