将 GD 图像缩放器转换为具有双三次锐化器的等效 ImageMagick
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【中文标题】将 GD 图像缩放器转换为具有双三次锐化器的等效 ImageMagick【英文标题】：Convert GD image resizer to the equivalent ImageMagick with bicubic sharper 【发布时间】：2014-06-11 09:45:14 【问题描述】：我有以下 php 脚本，它采用现有的 jpeg 图像并将其调整为较小的缩略图，同时为其添加 png 水印。 我遇到的问题是缩小是用 GD 库完成的，这使得输出拇指在缩小后不那么锐利（当不需要缩小尺寸时，它会更锐利，即如果原始尺寸和输出尺寸相同）。 有人告诉我，gd 中的调整大小算法不是很好，建议改用 ImageMagick，并带有自适应调整大小选项。我基本上想将脚本转换为使用 ImageMagick（双三次锐化）而不是 GD 库：
<?php
if (isset($_GET['image']) && isset($_GET['width']))
$image = $_GET['image'];
$max_width = $_GET['width'];
$max_height = 800;
$wmark='watermark.png';
$wmarks='watermark_s.png';
$wmarkm='watermark_m.png';
$wmarkno='nowatermark.png';
$noimg='noimg.png';
if (file_exists($image))
$cached='cache/'.preg_replace('/(\.\w+$)/',".$max_width\\1",$image);
if (file_exists($cached))
$cst=stat($cached);
$fst=stat($image);
if ($fst[9]<=$cst[9] && $fst[10]<=$cst[10])
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE']) && strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE'])>=$cst[9])
header("HTTP/1.0 304 Not Modified");
else
header('Content-type: image/jpeg');
header('Last-Modified: '.gmdate('D, d M Y H:i:s',$cst[9]).' GMT');
header('Cache-Control: private');
print file_get_contents($cached);
exit;
$size = GetImageSize($image);
$watermark_img = imagecreatefrompng($wmark);
$watermarks_img = imagecreatefrompng($wmarks);
$watermarkm_img = imagecreatefrompng($wmarkm);
$watermarkno_img = imagecreatefrompng($wmarkno);
$wmrk_size = getimagesize($wmark);
$wmrks_size = getimagesize($wmarks);
$wmrkm_size = getimagesize($wmarkm);
$wmrkno_size = getimagesize($wmarkno);
$width = $size[0];
$height = $size[1];
@$x_ratio = $max_width / $width;
@$y_ratio = $max_height / $height;
if (($width <= $max_width) && ($height <= $max_height))
$tn_height = $height;
$tn_width = $width;
else if (($x_ratio * $height) < $max_height)
$tn_height = ceil($x_ratio * $height);
$tn_width = $max_width;
else
$tn_height = $max_height;
$tn_width = ceil($y_ratio * $width);
if ((($tn_width) <>0) && (($tn_height)<>0))
$src = ImageCreateFromJPEG($image);
$dst = ImageCreateTrueColor($tn_width, $tn_height);
ImageCopyResampled($dst, $src, 0, 0, 0, 0, $tn_width, $tn_height, $width, $height);
//$dst = imagecreatefromjpeg($dst);
if (ImageSX($dst) > 300)
$posx = (ImageSX($dst) - ImageSX($watermark_img))/2;
$posy = (ImageSY($dst) - ImageSY($watermark_img))/2;
imagecopy($dst, $watermark_img, $posx, $posy, 0, 0, $wmrk_size[0], $wmrk_size[1]);
else
$posxs = (ImageSX($dst) - ImageSX($watermarkno_img))/2;
$posys = (ImageSY($dst) - ImageSY($watermarkno_img))/2;
imagecopy($dst, $watermarkno_img, $posxs, $posys, 0, 0, $wmrkno_size[0], $wmrkno_size[1]);
header('Content-type: image/jpeg');
header('Last-Modified: '.gmdate('D, d M Y H:i:s').' GMT');
header('Cache-Control: private');
ImageJPEG($dst, null, 90);
ImageJPEG($dst, $cached, 90);
ImageDestroy($src);
ImageDestroy($dst);
?>
【问题讨论】：
【参考方案1】：PHP 5.5 及更高版本有一个未记录的函数 imagesetinterpolation() 可让您更改插值方法。我只在源代码中看到过。我自己从来没有试过。您的里程可能会有所不同。
该函数有两个参数：图像资源和以下常量之一。
IMG_BELL
IMG_BESSEL
IMG_BILINEAR_FIXED
IMG_BICUBIC
IMG_BICUBIC_FIXED
IMG_BLACKMAN
IMG_BOX
IMG_BSPLINE
IMG_CATMULLROM
IMG_GAUSSIAN
IMG_GENERALIZED_CUBIC
IMG_HERMITE
IMG_HAMMING
IMG_HANNING
IMG_MITCHELL
IMG_POWER
IMG_QUADRATIC
IMG_SINC
IMG_NEAREST_NEIGHBOUR
IMG_WEIGHTED4
IMG_TRIANGLE
IMG_BILINEAR_FIXED 是默认设置。
【讨论】：
谢谢！我在 PHP 5.4 atm 上。明年将升级到 5.5，届时可能会进行研究，但目前仍需要解决我原来的帖子。干杯。 附注我也不知道列表中的任何插值是否相当于 bicubic-sharper（bicubic 可能意味着更平滑、更清晰等）。干杯。【参考方案2】：我自己使用 ImageMagick 对其进行了修改。比 GD 更清晰、更好的输出。 下面是修改后的版本。希望这可以帮助其他人。
<?php
if (isset($_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 $max_widthx$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 $max_widthx$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 $max_widthx$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;
?>
【讨论】：
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