max*_*ver 81 php gd jpeg image
在PHP中调整大图像大小的最有效方法是什么？
我目前正在使用GD功能imagecopyresampled来拍摄高分辨率图像,并将它们干净地调整到适合网页查看的大小(大约700像素宽,700像素高).
这适用于小(2 MB以下)的照片,整个调整大小操作在服务器上只需不到一秒钟.但是,该网站最终将为可能上传最大10 MB图像的摄影师提供服务(或者图像尺寸最大为5000x4000像素).
使用大图像执行此类调整大小操作往往会大幅增加内存使用量(较大的图像会使脚本的内存使用量超过80 MB).有没有办法让这个调整大小操作更有效率？我应该使用像ImageMagick这样的替代图像库吗？
现在,调整大小代码看起来像这样
function makeThumbnail($sourcefile, $endfile, $thumbwidth, $thumbheight, $quality) {
// Takes the sourcefile (path/to/image.jpg) and makes a thumbnail from it
// and places it at endfile (path/to/thumb.jpg).
// Load image and get image size.
$img = imagecreatefromjpeg($sourcefile);
$width = imagesx( $img );
$height = imagesy( $img );
if ($width > $height) {
$newwidth = $thumbwidth;
$divisor = $width / $thumbwidth;
$newheight = floor( $height / $divisor);
} else {
$newheight = $thumbheight;
$divisor = $height / $thumbheight;
$newwidth = floor( $width / $divisor );
}
// Create a new temporary image.
$tmpimg = imagecreatetruecolor( $newwidth, $newheight );
// Copy and resize old image into new image.
imagecopyresampled( $tmpimg, $img, 0, 0, 0, 0, $newwidth, $newheight, $width, $height );
// Save thumbnail into a file.
imagejpeg( $tmpimg, $endfile, $quality);
// release the memory
imagedestroy($tmpimg);
imagedestroy($img);
Grz*_*lik 45
人们说ImageMagick要快得多.最好只比较两个库并测量它.
其他人最好的东西,对你来说不是最好的.
另外,在我看来,ImageMagick有更好的API接口.
Kev*_*vin 19
这是我在项目中使用的php.net文档的一个片段,工作正常:
<?
function fastimagecopyresampled (&$dst_image, $src_image, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h, $quality = 3) {
// Plug-and-Play fastimagecopyresampled function replaces much slower imagecopyresampled.
// Just include this function and change all "imagecopyresampled" references to "fastimagecopyresampled".
// Typically from 30 to 60 times faster when reducing high resolution images down to thumbnail size using the default quality setting.
// Author: Tim Eckel - Date: 09/07/07 - Version: 1.1 - Project: FreeRingers.net - Freely distributable - These comments must remain.
//
// Optional "quality" parameter (defaults is 3). Fractional values are allowed, for example 1.5. Must be greater than zero.
// Between 0 and 1 = Fast, but mosaic results, closer to 0 increases the mosaic effect.
// 1 = Up to 350 times faster. Poor results, looks very similar to imagecopyresized.
// 2 = Up to 95 times faster. Images appear a little sharp, some prefer this over a quality of 3.
// 3 = Up to 60 times faster. Will give high quality smooth results very close to imagecopyresampled, just faster.
// 4 = Up to 25 times faster. Almost identical to imagecopyresampled for most images.
// 5 = No speedup. Just uses imagecopyresampled, no advantage over imagecopyresampled.
if (empty($src_image) || empty($dst_image) || $quality <= 0) { return false; }
if ($quality < 5 && (($dst_w * $quality) < $src_w || ($dst_h * $quality) < $src_h)) {
$temp = imagecreatetruecolor ($dst_w * $quality + 1, $dst_h * $quality + 1);
imagecopyresized ($temp, $src_image, 0, 0, $src_x, $src_y, $dst_w * $quality + 1, $dst_h * $quality + 1, $src_w, $src_h);
imagecopyresampled ($dst_image, $temp, $dst_x, $dst_y, 0, 0, $dst_w, $dst_h, $dst_w * $quality, $dst_h * $quality);
imagedestroy ($temp);
} else imagecopyresampled ($dst_image, $src_image, $dst_x, $dst_y, $src_x, $src_y, $dst_w, $dst_h, $src_w, $src_h);
return true;
}
?>
http://us.php.net/manual/en/function.imagecopyresampled.php#77679
Ste*_*e-o 10
对于较大的图像,使用libjpeg调整ImageMagick中的图像负载大小,从而显着减少内存使用并提高性能,GD不可能实现.
$im = new Imagick();
try {
$im->pingImage($file_name);
} catch (ImagickException $e) {
throw new Exception(_('Invalid or corrupted image file, please try uploading another image.'));
}
$width = $im->getImageWidth();
$height = $im->getImageHeight();
if ($width > $config['width_threshold'] || $height > $config['height_threshold'])
{
try {
/* send thumbnail parameters to Imagick so that libjpeg can resize images
* as they are loaded instead of consuming additional resources to pass back
* to PHP.
*/
$fitbyWidth = ($config['width_threshold'] / $width) > ($config['height_threshold'] / $height);
$aspectRatio = $height / $width;
if ($fitbyWidth) {
$im->setSize($config['width_threshold'], abs($width * $aspectRatio));
} else {
$im->setSize(abs($height / $aspectRatio), $config['height_threshold']);
}
$im->readImage($file_name);
/* Imagick::thumbnailImage(fit = true) has a bug that it does fit both dimensions
*/
// $im->thumbnailImage($config['width_threshold'], $config['height_threshold'], true);
// workaround:
if ($fitbyWidth) {
$im->thumbnailImage($config['width_threshold'], 0, false);
} else {
$im->thumbnailImage(0, $config['height_threshold'], false);
}
$im->setImageFileName($thumbnail_name);
$im->writeImage();
}
catch (ImagickException $e)
{
header('HTTP/1.1 500 Internal Server Error');
throw new Exception(_('An error occured reszing the image.'));
}
}
/* cleanup Imagick
*/
$im->destroy();
从你的问题来看,你似乎对GD有点新意,我会分享一些我的经历,也许这有点偏离主题,但我认为对你这样的新人来说会有所帮助:
第1步,验证文件.使用以下函数检查$_FILES['image']['tmp_name']文件是否为有效文件:
function getContentsFromImage($image) {
if (@is_file($image) == true) {
return file_get_contents($image);
} else {
throw new \Exception('Invalid image');
}
}
$contents = getContentsFromImage($_FILES['image']['tmp_name']);
步骤2,获取文件格式尝试使用finfo扩展的以下函数来检查文件的文件格式(内容).你会说为什么不用它$_FILES["image"]["type"]来检查文件格式？由于它仅检查文件的扩展名而不是文件内容,如果有人重命名原名文件world.png到world.jpg,$_FILES["image"]["type"]将返回JPEG不PNG,所以$_FILES["image"]["type"]可能会返回错误的结果.
function getFormatFromContents($contents) {
$finfo = new \finfo();
$mimetype = $finfo->buffer($contents, FILEINFO_MIME_TYPE);
switch ($mimetype) {
case 'image/jpeg':
return 'jpeg';
break;
case 'image/png':
return 'png';
break;
case 'image/gif':
return 'gif';
break;
default:
throw new \Exception('Unknown or unsupported image format');
}
}
$format = getFormatFromContents($contents);
Step.3,获取GD资源从我们之前的内容中获取GD资源:
function getGDResourceFromContents($contents) {
$resource = @imagecreatefromstring($contents);
if ($resource == false) {
throw new \Exception('Cannot process image');
}
return $resource;
}
$resource = getGDResourceFromContents($contents);
第4步,获取图像尺寸现在,您可以使用以下简单代码获取图像尺寸:
$width = imagesx($resource);
$height = imagesy($resource);
现在,让我们看看我们从原始图像中获得了什么变量:
$contents, $format, $resource, $width, $height
OK, lets move on
步骤5,计算调整大小的图像参数这一步与你的问题有关,以下函数的目的是为GD函数获取resize参数imagecopyresampled(),代码有点长,但它工作得很好,它甚至有三个选项:stretch,shrink ,并填写.
stretch:输出图像的尺寸与您设置的新尺寸相同.不会保持高/宽比.
缩小:输出图像的尺寸不会超过您给出的新尺寸,并保持图像的高度/宽度比.
填充:输出图像的尺寸与您给出的新尺寸相同,如果需要,它将裁剪并调整图像大小,并保持图像高/宽比.您可以在问题中使用此选项.
function getResizeArgs($width, $height, $newwidth, $newheight, $option) {
if ($option === 'stretch') {
if ($width === $newwidth && $height === $newheight) {
return false;
}
$dst_w = $newwidth;
$dst_h = $newheight;
$src_w = $width;
$src_h = $height;
$src_x = 0;
$src_y = 0;
} else if ($option === 'shrink') {
if ($width <= $newwidth && $height <= $newheight) {
return false;
} else if ($width / $height >= $newwidth / $newheight) {
$dst_w = $newwidth;
$dst_h = (int) round(($newwidth * $height) / $width);
} else {
$dst_w = (int) round(($newheight * $width) / $height);
$dst_h = $newheight;
}
$src_x = 0;
$src_y = 0;
$src_w = $width;
$src_h = $height;
} else if ($option === 'fill') {
if ($width === $newwidth && $height === $newheight) {
return false;
}
if ($width / $height >= $newwidth / $newheight) {
$src_w = (int) round(($newwidth * $height) / $newheight);
$src_h = $height;
$src_x = (int) round(($width - $src_w) / 2);
$src_y = 0;
} else {
$src_w = $width;
$src_h = (int) round(($width * $newheight) / $newwidth);
$src_x = 0;
$src_y = (int) round(($height - $src_h) / 2);
}
$dst_w = $newwidth;
$dst_h = $newheight;
}
if ($src_w < 1 || $src_h < 1) {
throw new \Exception('Image width or height is too small');
}
return array(
'dst_x' => 0,
'dst_y' => 0,
'src_x' => $src_x,
'src_y' => $src_y,
'dst_w' => $dst_w,
'dst_h' => $dst_h,
'src_w' => $src_w,
'src_h' => $src_h
);
}
$args = getResizeArgs($width, $height, 150, 170, 'fill');
步骤6,调整图像使用$args,$width,$height,$format我们从上面钻进了以下功能和$资源,并得到调整后的图像的新资源:
function runResize($width, $height, $format, $resource, $args) {
if ($args === false) {
return; //if $args equal to false, this means no resize occurs;
}
$newimage = imagecreatetruecolor($args['dst_w'], $args['dst_h']);
if ($format === 'png') {
imagealphablending($newimage, false);
imagesavealpha($newimage, true);
$transparentindex = imagecolorallocatealpha($newimage, 255, 255, 255, 127);
imagefill($newimage, 0, 0, $transparentindex);
} else if ($format === 'gif') {
$transparentindex = imagecolorallocatealpha($newimage, 255, 255, 255, 127);
imagefill($newimage, 0, 0, $transparentindex);
imagecolortransparent($newimage, $transparentindex);
}
imagecopyresampled($newimage, $resource, $args['dst_x'], $args['dst_y'], $args['src_x'], $args['src_y'], $args['dst_w'], $args['dst_h'], $args['src_w'], $args['src_h']);
imagedestroy($resource);
return $newimage;
}
$newresource = runResize($width, $height, $format, $resource, $args);
步骤7,获取新内容,使用以下函数从新的GD资源获取内容:
function getContentsFromGDResource($resource, $format) {
ob_start();
switch ($format) {
case 'gif':
imagegif($resource);
break;
case 'jpeg':
imagejpeg($resource, NULL, 100);
break;
case 'png':
imagepng($resource, NULL, 9);
}
$contents = ob_get_contents();
ob_end_clean();
return $contents;
}
$newcontents = getContentsFromGDResource($newresource, $format);
步骤8获取扩展,使用以下函数从图像格式获取扩展(注意,图像格式不等于图像扩展名):
function getExtensionFromFormat($format) {
switch ($format) {
case 'gif':
return 'gif';
break;
case 'jpeg':
return 'jpg';
break;
case 'png':
return 'png';
}
}
$extension = getExtensionFromFormat($format);
步骤9保存图像如果我们有一个名为mike的用户,您可以执行以下操作,它将保存到与此php脚本相同的文件夹中:
$user_name = 'mike';
$filename = $user_name . '.' . $extension;
file_put_contents($filename, $newcontents);
步骤10破坏资源不要忘记破坏GD资源!
imagedestroy($newresource);
或者您可以将所有代码写入类中,只需使用以下代码:
public function __destruct() {
@imagedestroy($this->resource);
}
提示
我建议不要转换用户上传的文件格式,你会遇到很多问题.