PHP 中有效的 JPEG 图像大小调整

Efficient JPEG Image Resizing in PHP

提问by maxsilver

What's the most efficient way to resize large images in PHP?

在 PHP 中调整大图像大小的最有效方法是什么？

I'm currently using the GDfunction imagecopyresampled to take high resolution images, and cleanly resize them down to a size for web viewing (roughly 700 pixels wide by 700 pixels tall).

我目前正在使用GD函数 imagecopyresampled 来获取高分辨率图像，并将它们干净地调整为适合 Web 查看的大小（大约 700 像素宽 x 700 像素高）。

This works great on small (under 2 MB) photos and the entire resize operation takes less than a second on the server. However, the site will eventually service photographers who may be uploading images up to 10 MB in size (or images up to 5000x4000 pixels in size).

这对小（小于 2 MB）照片很有效，整个调整大小操作在服务器上不到一秒钟。但是，该网站最终将为上传最大 10 MB 图像（或最大 5000x4000 像素的图像）的摄影师提供服务。

Doing this kind of resize operation with large images tends to increase the memory usage by a very large margin (larger images can spike the memory usage for the script past 80 MB). Is there any way to make this resize operation more efficient? Should I be using an alternate image library such as ImageMagick?

对大图像执行这种调整大小操作往往会大大增加内存使用量（较大的图像可能会使脚本的内存使用量超过 80 MB）。有什么方法可以使这种调整大小操作更有效吗？我应该使用替代图像库，例如ImageMagick吗？

Right now, the resize code looks something like this

现在，调整大小的代码看起来像这样

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);

采纳答案by Grzegorz Gierlik

People say that ImageMagick is much faster. At best just compare both libraries and measure that.

人们说 ImageMagick 快得多。充其量只是比较两个库并对其进行测量。

1. Prepare 1000 typical images.
2. Write two scripts -- one for GD, one for ImageMagick.
3. Run both of them a few times.
4. Compare results (total execution time, CPU and I/O usage, result image quality).

1. 准备 1000 张典型图像。
2. 编写两个脚本——一个用于 GD，一个用于 ImageMagick。
3. 运行它们几次。
4. 比较结果（总执行时间、CPU 和 I/O 使用率、结果图像质量）。

Something which the best everyone else, could not be the best for you.

其他人最好的东西，对你来说不可能是最好的。

Also, in my opinion, ImageMagick has much better API interface.

另外，在我看来，ImageMagick 有更好的 API 接口。

回答by Kevin

Here's a snippet from the php.net docs that I've used in a project and works fine:

这是我在项目中使用的 php.net 文档中的一个片段，并且工作正常：

<?
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

http://us.php.net/manual/en/function.imagecopyresampled.php#77679

回答by phenry

phpThumbuses ImageMagick whenever possible for speed (falling back to GD if necessary) and seems to cache pretty well to reduce the load on the server. It's pretty lightweight to try out (to resize an image, just call phpThumb.php with a GET query that includes the graphic filename and output dimensions), so you might give it a shot to see if it meets your needs.

phpThumb尽可能使用 ImageMagick 来提高速度（必要时回退到 GD）并且似乎可以很好地缓存以减少服务器上的负载。试用它非常轻巧（要调整图像大小，只需使用包含图形文件名和输出尺寸的 GET 查询调用 phpThumb.php），因此您可以尝试一下，看看它是否满足您的需求。

回答by Steve-o

For larger images use libjpeg to resize on image load in ImageMagick and thereby significantly reducing memory usage and improving performance, it is not possible with GD.

对于较大的图像，在 ImageMagick 中使用 libjpeg 调整图像加载大小，从而显着减少内存使用并提高性能，这是 GD 无法实现的。

$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();

回答by nut

From you quesion, it seems you are kinda new to GD, I will share some experence of mine, maybe this is a bit off topic, but I think it will be helpful to someone new to GD like you:

从你的问题来看，你似乎对GD有点陌生，我将分享我的一些经验，也许这有点离题，但我认为这对像你这样的GD新手会有帮助：

Step 1, validate file.Use the following function to check if the $_FILES['image']['tmp_name']file is valid file:

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']);

Step 2, get file formatTry the following function with finfo extension to check file format of the file(contents). You would say why don't you just use $_FILES["image"]["type"]to check file format? Because it ONLYcheck file extension not file contents, if someone rename a file originally called world.pngto world.jpg, $_FILES["image"]["type"]will return jpeg not png, so $_FILES["image"]["type"]may return wrong result.

第 2 步，获取文件格式尝试以下带有 finfo 扩展名的函数来检查文件（内容）的文件格式。你会说你为什么不只是$_FILES["image"]["type"]用来检查文件格式？由于它仅检查文件的扩展名而不是文件内容，如果有人重命名原名文件world.png到world.jpg，$_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, Get GD resourceGet GD resource from contents we have before:

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);

Step 4, get image dimensionNow you can get image dimension with the following simple code:

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);

Now,Let's see what variable we got from the original image then:

现在，让我们看看我们从原始图像中得到了什么变量：

       $contents, $format, $resource, $width, $height
       OK, lets move on

Step 5, calculate resized image argumentsThis step is related to your question, the purpose of the following function is to get resize arguments for GD function imagecopyresampled(), the code is kinda long, but it works great, it even has three options: stretch, shrink, and fill.

Step 5, 计算resized image arguments这一步和你的问题有关，下面这个函数的目的是获取GD函数的resize参数imagecopyresampled()，代码有点长，但效果很好，它甚至有三个选项：拉伸，收缩，并填充。

stretch: output image's dimension is the same as the new dimension you set. Won't keep height/width ratio.

拉伸：输出图像的尺寸与您设置的新尺寸相同。不会保持高/宽比。

shrink: output image's dimension won't exceed the new dimension you give, and keep image height/width ratio.

收缩：输出图像的尺寸不会超过您提供的新尺寸，并保持图像的高宽比。

fill: output image's dimension will be the same as new dimension you give, it will crop & resizeimage if needed, and keep image height/width ratio. This option is what you need in your question.

fill：输出图像的尺寸将与您提供的新尺寸相同，如果需要，它将裁剪和调整图像大小，并保持图像的高/宽比。此选项是您在问题中所需要的。

   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');

Step 6, resize imageUse $args, $width, $height, $formatand $resource we got from above into the following function and get the new resource of the resized image:

第六步，调整图片大小将我们从上面得到的$args, $width, $height,$format和 $resource使用到下面的函数中，得到调整后图片的新资源：

   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);

Step 7, get new contents, Use the following function to get contents from the new GD resource:

第七步，获取新内容，使用如下函数从新的GD资源中获取内容：

   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);

Step 8 get extension, Use the following function to get extension of from image format(note, image format is not equal to image extension):

第8步获取扩展名，使用以下函数从图像格式中获取扩展名（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);

Step 9 save imageIf we have a user named mike, you can do the following, it will save to the same folder as this php script:

步骤 9 保存图片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);

Step 10 destroy resourceDon't forget destroy GD resource!

第10步销毁资源不要忘记销毁GD资源！

imagedestroy($newresource);

or you can write all your code into a class, and simply use the following:

或者您可以将所有代码写入一个类，只需使用以下内容：

   public function __destruct() {
      @imagedestroy($this->resource);
   }

TIPS

提示

I recommend not to convert file format that user upload, you will meet many problems.

我建议不要转换用户上传的文件格式，你会遇到很多问题。

回答by Salman A

I suggest that you work something along these lines:

我建议您按照以下方式工作：

1. Perform a getimagesize( ) on the uploaded file to check image type and size
2. Save any uploaded JPEG image smaller than 700x700px in to the destination folder "as-is"
3. Use GD library for medium size images (see this article for code sample: Resize Images Using PHP and GD Library)
4. Use ImageMagick for large images. You can use ImageMagick in background if you prefer.

1. 对上传的文件执行 getimagesize( ) 以检查图像类型和大小
2. 将任何上传的小于 700x700px 的 JPEG 图像“按原样”保存到目标文件夹中
3. 使用 GD 库处理中等大小的图像（代码示例见这篇文章：使用 PHP 和 GD 库调整图像大小）
4. 对大图像使用 ImageMagick。如果您愿意，您可以在后台使用 ImageMagick。

To use ImageMagick in background, move the uploaded files to a temporary folder and schedule a CRON job that "convert"s all files to jpeg and resizes them accordingly. See command syntax at: imagemagick-command line processing

要在后台使用 ImageMagick，请将上传的文件移动到一个临时文件夹并安排一个 CRON 作业，将所有文件“转换”为 jpeg 并相应地调整它们的大小。参见命令语法：imagemagick-command line processing

You can prompt the user that file is uploaded and scheduled to be processed. The CRON job could be scheduled to run daily at a specific interval. The source image could be deleted after processing to assure that an image is not processed twice.

您可以提示用户文件已上传并计划处理。CRON 作业可以安排为每天以特定时间间隔运行。处理后可以删除源图像，以确保图像不会被处理两次。

回答by alessioalex

I've heard big things about the Imagick library, unfortunately I couldn't install it at my work computer and neither at home (and trust me, I spent hours and hours on all kinds of forums).

我听说过有关 Imagick 库的大事，不幸的是我无法将它安装在我的工作计算机上，也无法安装在家里（相信我，我在各种论坛上花费了数小时和数小时）。

Afterwords, I've decided to try this PHP class:

后记，我决定尝试这个 PHP 类：

http://www.verot.net/php_class_upload.htm

http://www.verot.net/php_class_upload.htm

It's pretty cool and I can resize all kinds of images (I can convert them to JPG also).

它非常酷，我可以调整各种图像的大小（我也可以将它们转换为 JPG）。

回答by Alasdair

ImageMagick is multithreaded, so it appears to be faster, but actually uses a lot more resources than GD. If you ran several PHP scripts in parallel all using GD then they'd beat ImageMagick in speed for simple operations. ExactImage is less powerful than ImageMagick but a lot faster, though not available through PHP, you'll have to install it on the server and run it through exec.

ImageMagick 是多线程的，所以它看起来更快，但实际上比 GD 使用更多的资源。如果您使用 GD 并行运行多个 PHP 脚本，那么它们会在简单操作的速度上击败 ImageMagick。ExactImage 不如 ImageMagick 强大，但速度要快得多，虽然不能通过 PHP 获得，但您必须在服务器上安装它并通过exec.

回答by Adnan

For larger images use phpThumb(). Here is how to use it: http://abcoder.com/php/problem-with-resizing-corrupted-images-using-php-image-functions/. It also works for large corrupted images.

对于较大的图像，请使用phpThumb()。这是如何使用它：http: //abcoder.com/php/problem-with-resizing-corrupted-images-using-php-image-functions/。它也适用于大型损坏的图像。