我自己使用 ImageMagick 对其进行了修改。比 GD 更清晰、更好的输出。
下面是修改后的版本。希望这可以帮助其他人。
<?php
if (isset($_GET['image']) && isset($_GET['width']) && is_numeric($_GET['width']) ) {
// Get image name
$original_image = $_GET['image'];
// Watermarks
$wmark='watermark.png'; //largest watermark
$wmarkm='watermark_m.png'; //medium watermark
$wmarks='watermark_s.png'; //smallest watermark
$wmarkno='nowatermark.png'; //No watermark
// Maximum image width
$max_width = (int)$_GET['width'];
// Maximum image height
$max_height = "800";
if (file_exists($original_image)) {
$cached='cache/'.preg_replace('/(\.\w+$)/',".{$max_width}\\1",$original_image);
if (file_exists($cached)) {
$cst=stat($cached);
$fst=stat($original_image);
if ($fst[9]<=$cst[9] && $fst[10]<=$cst[10]) {
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])>=$cst[9]) {
header('Last-Modified: '.gmdate('D, d M Y H:i:s', filemtime($cached)).' GMT', true, 304);
} else {
header('Content-type: image/jpeg');
header('Last-Modified: '.gmdate('D, d M Y H:i:s',$cst[9]).' GMT');
header('Cache-Control: private');
readfile($cached);
}
exit;
}
}
if ($max_width > 300) {
$watermark=$wmark;
} elseif ($max_width > 152 && $max_width < 300) {
$watermark=$wmarkm;
}elseif ($max_width > 50 && $max_width < 151){
$watermark=$wmarks;
} else {
$watermark=$wmarkno;
}
// Resize the image, save and output to browser with headers
exec("convert -filter Lanczos $original_image -thumbnail {$max_width}x{$max_height} -quality 90 {$watermark} -gravity center -unsharp 2x0.5+0.2+0 -composite {$cached}");
header('Content-type: image/jpeg');
header('Last-Modified: '.gmdate('D, d M Y H:i:s').' GMT');
header('Cache-Control: private');
readfile($cached);
}
}
?>
编辑
似乎 ImageMagick 在我的服务器上使用了过多的资源，因为它正在批量调整大小。我最终决定改用 GraphicsMagick，它可以输出我需要的相同图像质量、几乎相同的文件大小，同时工作速度更快，并且在我的服务器上使用更少的资源。
为此，我刚刚安装了 GraphicsMagick 并将 exec 行从：
exec("convert -filter Lanczos $original_image -thumbnail {$max_width}x{$max_height} -quality 90 {$watermark} -gravity center -unsharp 2x0.5+0.2+0 -composite {$cached}");
收件人：
//create the resized image
exec("gm convert -filter Lanczos {$original_image} -thumbnail {$max_width}x{$max_height} -quality 90 -unsharp 2x0.5+0.2+0 {$cached}");
//apply the watermark and recreate the watermarked image, overwriting the previously resized image
exec("gm composite -quality 90 -dissolve 100 -gravity center {$watermark} {$cached} {$cached}");
编辑 2
对于任何想要或需要继续使用 GD 的人来说，另一种方法是使用以下出色的反锐化蒙版功能（取自 http://vikjavev.no/computing/ump.php）：
<?php
/*
New:
- In version 2.1 (February 26 2007) Tom Bishop has done some important speed enhancements.
- From version 2 (July 17 2006) the script uses the imageconvolution function in PHP
version >= 5.1, which improves the performance considerably.
Unsharp masking is a traditional darkroom technique that has proven very suitable for
digital imaging. The principle of unsharp masking is to create a blurred copy of the image
and compare it to the underlying original. The difference in colour values
between the two images is greatest for the pixels near sharp edges. When this
difference is subtracted from the original image, the edges will be
accentuated.
The Amount parameter simply says how much of the effect you want. 100 is 'normal'.
Radius is the radius of the blurring circle of the mask. 'Threshold' is the least
difference in colour values that is allowed between the original and the mask. In practice
this means that low-contrast areas of the picture are left unrendered whereas edges
are treated normally. This is good for pictures of e.g. skin or blue skies.
Any suggenstions for improvement of the algorithm, expecially regarding the speed
and the roundoff errors in the Gaussian blur process, are welcome.
*/
function UnsharpMask($img, $amount, $radius, $threshold) {
////////////////////////////////////////////////////////////////////////////////////////////////
////
//// Unsharp Mask for PHP - version 2.1.1
////
//// Unsharp mask algorithm by Torstein H?nsi 2003-07.
//// thoensi_at_netcom_dot_no.
//// Please leave this notice.
////
///////////////////////////////////////////////////////////////////////////////////////////////
// $img is an image that is already created within php using
// imgcreatetruecolor. No url! $img must be a truecolor image.
// Attempt to calibrate the parameters to Photoshop:
if ($amount > 500) $amount = 500;
$amount = $amount * 0.016;
if ($radius > 50) $radius = 50;
$radius = $radius * 2;
if ($threshold > 255) $threshold = 255;
$radius = abs(round($radius)); // Only integers make sense.
if ($radius == 0) {
return $img; imagedestroy($img); break; }
$w = imagesx($img); $h = imagesy($img);
$imgCanvas = imagecreatetruecolor($w, $h);
$imgBlur = imagecreatetruecolor($w, $h);
// Gaussian blur matrix:
//
// 1 2 1
// 2 4 2
// 1 2 1
//
//////////////////////////////////////////////////
if (function_exists('imageconvolution')) { // PHP >= 5.1
$matrix = array(
array( 1, 2, 1 ),
array( 2, 4, 2 ),
array( 1, 2, 1 )
);
imagecopy ($imgBlur, $img, 0, 0, 0, 0, $w, $h);
imageconvolution($imgBlur, $matrix, 16, 0);
}
else {
// Move copies of the image around one pixel at the time and merge them with weight
// according to the matrix. The same matrix is simply repeated for higher radii.
for ($i = 0; $i < $radius; $i++) {
imagecopy ($imgBlur, $img, 0, 0, 1, 0, $w - 1, $h); // left
imagecopymerge ($imgBlur, $img, 1, 0, 0, 0, $w, $h, 50); // right
imagecopymerge ($imgBlur, $img, 0, 0, 0, 0, $w, $h, 50); // center
imagecopy ($imgCanvas, $imgBlur, 0, 0, 0, 0, $w, $h);
imagecopymerge ($imgBlur, $imgCanvas, 0, 0, 0, 1, $w, $h - 1, 33.33333 ); // up
imagecopymerge ($imgBlur, $imgCanvas, 0, 1, 0, 0, $w, $h, 25); // down
}
}
if($threshold>0){
// Calculate the difference between the blurred pixels and the original
// and set the pixels
for ($x = 0; $x < $w-1; $x++) { // each row
for ($y = 0; $y < $h; $y++) { // each pixel
$rgbOrig = ImageColorAt($img, $x, $y);
$rOrig = (($rgbOrig >> 16) & 0xFF);
$gOrig = (($rgbOrig >> 8) & 0xFF);
$bOrig = ($rgbOrig & 0xFF);
$rgbBlur = ImageColorAt($imgBlur, $x, $y);
$rBlur = (($rgbBlur >> 16) & 0xFF);
$gBlur = (($rgbBlur >> 8) & 0xFF);
$bBlur = ($rgbBlur & 0xFF);
// When the masked pixels differ less from the original
// than the threshold specifies, they are set to their original value.
$rNew = (abs($rOrig - $rBlur) >= $threshold)
? max(0, min(255, ($amount * ($rOrig - $rBlur)) + $rOrig))
: $rOrig;
$gNew = (abs($gOrig - $gBlur) >= $threshold)
? max(0, min(255, ($amount * ($gOrig - $gBlur)) + $gOrig))
: $gOrig;
$bNew = (abs($bOrig - $bBlur) >= $threshold)
? max(0, min(255, ($amount * ($bOrig - $bBlur)) + $bOrig))
: $bOrig;
if (($rOrig != $rNew) || ($gOrig != $gNew) || ($bOrig != $bNew)) {
$pixCol = ImageColorAllocate($img, $rNew, $gNew, $bNew);
ImageSetPixel($img, $x, $y, $pixCol);
}
}
}
}
else{
for ($x = 0; $x < $w; $x++) { // each row
for ($y = 0; $y < $h; $y++) { // each pixel
$rgbOrig = ImageColorAt($img, $x, $y);
$rOrig = (($rgbOrig >> 16) & 0xFF);
$gOrig = (($rgbOrig >> 8) & 0xFF);
$bOrig = ($rgbOrig & 0xFF);
$rgbBlur = ImageColorAt($imgBlur, $x, $y);
$rBlur = (($rgbBlur >> 16) & 0xFF);
$gBlur = (($rgbBlur >> 8) & 0xFF);
$bBlur = ($rgbBlur & 0xFF);
$rNew = ($amount * ($rOrig - $rBlur)) + $rOrig;
if($rNew>255){$rNew=255;}
elseif($rNew<0){$rNew=0;}
$gNew = ($amount * ($gOrig - $gBlur)) + $gOrig;
if($gNew>255){$gNew=255;}
elseif($gNew<0){$gNew=0;}
$bNew = ($amount * ($bOrig - $bBlur)) + $bOrig;
if($bNew>255){$bNew=255;}
elseif($bNew<0){$bNew=0;}
$rgbNew = ($rNew << 16) + ($gNew <<8) + $bNew;
ImageSetPixel($img, $x, $y, $rgbNew);
}
}
}
imagedestroy($imgCanvas);
imagedestroy($imgBlur);
return $img;
}
?>