一般来说，我不建议修改原始上传的图像文件，以防我们可能需要重新生成中等大小的文件。

但让我们看看是否有可能：-）

通常，我们可以让WordPress通过以下方式选择图像编辑器，该编辑器取决于GD或Imagick等模块：

$editor = wp_get_image_editor( $file );

让图像编辑器通过以下方法处理事情是很有用的set_quality() 和save(). 我们可以在@MerchantWeb提到的上传后调整图像大小插件中看到这样一个使用示例。核心也以各种方式使用它。

插件钩住wp_handle_upload 据我所知，过滤器可以修改原始上传的jpeg图像文件。

A) 因此，我们可以使用如下内容，在上载过程中修改原始jpeg图像文件的质量（例如，90）：

/**
 * A) Modify the quality of original jpeg images to 90, during uploads
 */
add_filter( \'wp_handle_upload\', function( $data )
{
    if( ! isset( $data[\'file\'] ) || ! isset( $data[\'type\'] ) )
        return $data;

    // Target jpeg images       
    if( in_array( $data[\'type\'], [ \'image/jpg\', \'image/jpeg\' ] ) )
    {
        // Check for a valid image editor
        $editor = wp_get_image_editor( $data[\'file\'] );    
        if( ! is_wp_error( $editor ) )
        {
            // Set the new image quality
            $result = $editor->set_quality( 90 );

            // Re-save the original image file
            if( ! is_wp_error( $result ) )
                $editor->save( $data[\'file\'] );
        }
    }
    return $data;
} );

B) 如果我们看看media_handle_upload() 函数，我们可以考虑连接到wp_generate_attachment_metadata 改为过滤，以修改原始jpeg图像文件，after 已生成中间尺寸。

下面是一个示例（PHP 5.4+）：

/**
 * B) Modify the quality of original jpeg images to 90, during uploads
 */
add_filter( \'wp_generate_attachment_metadata\', function( $metadata, $attachment_id ) 
{
    $file = get_attached_file( $attachment_id );
    $type = get_post_mime_type( $attachment_id );

    // Target jpeg images
    if( in_array( $type, [ \'image/jpg\', \'image/jpeg\' ] ) )
    {
        // Check for a valid image editor
        $editor = wp_get_image_editor( $file );
        if( ! is_wp_error( $editor ) )
        {
            // Set the new image quality
            $result = $editor->set_quality( 90 );

            // Re-save the original image file
            if( ! is_wp_error( $result ) )
                $editor->save( $file );
        }
    }   
    return $metadata;
}, 10, 2 );

我们可能还需要在测试时将质量设置得非常低，以查看它是否有效；-）

Note: 这些只是演示，需要进一步测试。

Update: 只是用厨房挂钟的图像做了一些简单的测试。在这里，我们可以看到，当以质量5重新保存全尺寸图像时，所有中间尺寸：

质量也很低

这个答案可以帮助您：https://wordpress.stackexchange.com/a/69287/92649

不过，您需要以比“大”更高的分辨率上传图像才能达到这种效果

上传后有一个名为Resize Image的插件：

<?php
/*
Plugin Name: Resize Image After Upload
Plugin URI: https://wordpress.org/plugins/resize-image-after-upload/
Description: Simple plugin to automatically resize uploaded images to within specified maximum width and height. Also has option to force recompression of JPEGs. Configuration options found under <a href="options-general.php?page=resize-after-upload">Settings > Resize Image Upload</a>
Author: iamphilrae
Version: 1.7.2
Author URI: http://www.philr.ae/

Copyright (C) 2015 iamphilrae

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

$PLUGIN_VERSION = \'1.7.2\';
$DEBUG_LOGGER = false;


// Default plugin values
if(get_option(\'jr_resizeupload_version\') != $PLUGIN_VERSION) {

  add_option(\'jr_resizeupload_version\',             $PLUGIN_VERSION, \'\',\'yes\');
  add_option(\'jr_resizeupload_width\',               \'1200\', \'\', \'yes\');
  add_option(\'jr_resizeupload_height\',              \'1200\', \'\', \'yes\');
  add_option(\'jr_resizeupload_quality\',             \'90\', \'\', \'yes\');
  add_option(\'jr_resizeupload_resize_yesno\',        \'yes\', \'\',\'yes\');
  add_option(\'jr_resizeupload_recompress_yesno\',    \'no\', \'\',\'yes\');
  add_option(\'jr_resizeupload_convertbmp_yesno\',    \'no\', \'\', \'yes\');
  add_option(\'jr_resizeupload_convertpng_yesno\',    \'no\', \'\', \'yes\');
  add_option(\'jr_resizeupload_convertgif_yesno\',    \'no\', \'\', \'yes\');
}



// Hook in the options page
add_action(\'admin_menu\', \'jr_uploadresize_options_page\');

// Hook the function to the upload handler
add_action(\'wp_handle_upload\', \'jr_uploadresize_resize\');




/**
* Add the options page
*/
function jr_uploadresize_options_page(){
    if(function_exists(\'add_options_page\')){
        add_options_page(
            \'Resize Image After Upload\',
            \'Resize Image Upload\',
            \'manage_options\',
            \'resize-after-upload\',
            \'jr_uploadresize_options\'
        );
    }
} // function jr_uploadresize_options_page(){



/**
* Define the Options page for the plugin
*/
function jr_uploadresize_options(){

  if(isset($_POST[\'jr_options_update\'])) {

    $resizing_enabled = trim(esc_sql($_POST[\'yesno\']));
    $force_jpeg_recompression   = trim(esc_sql($_POST[\'recompress_yesno\']));

    $max_width   = trim(esc_sql($_POST[\'maxwidth\']));
    $max_height  = trim(esc_sql($_POST[\'maxheight\']));
    $compression_level    = trim(esc_sql($_POST[\'quality\']));

    $convert_png_to_jpg = trim(esc_sql(isset($_POST[\'convertpng\']) ? $_POST[\'convertpng\'] : \'no\'));
    $convert_gif_to_jpg = trim(esc_sql(isset($_POST[\'convertgif\']) ? $_POST[\'convertgif\'] : \'no\'));
    $convert_bmp_to_jpg = trim(esc_sql(isset($_POST[\'convertbmp\']) ? $_POST[\'convertbmp\'] : \'no\'));


    // If input is not an integer, use previous setting
    $max_width = ($max_width == \'\') ? 0 : $max_width;
    $max_width = (ctype_digit(strval($max_width)) == false) ? get_option(\'jr_resizeupload_width\') : $max_width;
    update_option(\'jr_resizeupload_width\',$max_width);


    $max_height = ($max_height == \'\') ? 0 : $max_height;
    $max_height = (ctype_digit(strval($max_height)) == false) ? get_option(\'jr_resizeupload_height\') : $max_height;
    update_option(\'jr_resizeupload_height\',$max_height);


    $compression_level = ($compression_level == \'\') ? 1 : $compression_level;
    $compression_level = (ctype_digit(strval($compression_level)) == false) ? get_option(\'jr_resizeupload_quality\') : $compression_level;

    if($compression_level < 1) {
        $compression_level = 1;
    }
    else if($compression_level > 100) {
        $compression_level = 100;
    }

    update_option(\'jr_resizeupload_quality\',$compression_level);




    if ($resizing_enabled == \'yes\') {
      update_option(\'jr_resizeupload_resize_yesno\',\'yes\'); }
    else {
      update_option(\'jr_resizeupload_resize_yesno\',\'no\'); }


    if ($force_jpeg_recompression == \'yes\') {
      update_option(\'jr_resizeupload_recompress_yesno\',\'yes\'); }
    else {
      update_option(\'jr_resizeupload_recompress_yesno\',\'no\'); }


    if ($convert_png_to_jpg == \'yes\') {
      update_option(\'jr_resizeupload_convertpng_yesno\',\'yes\'); }
    else {
      update_option(\'jr_resizeupload_convertpng_yesno\',\'no\'); }

    if ($convert_gif_to_jpg == \'yes\') {
      update_option(\'jr_resizeupload_convertgif_yesno\',\'yes\'); }
    else {
      update_option(\'jr_resizeupload_convertgif_yesno\',\'no\'); }

    if ($convert_bmp_to_jpg == \'yes\') {
      update_option(\'jr_resizeupload_convertbmp_yesno\',\'yes\'); }
    else {
      update_option(\'jr_resizeupload_convertbmp_yesno\',\'no\'); }



    echo(\'<div id="message" class="updated fade"><p><strong>Options have been updated.</strong></p></div>\');
  } // if



  // get options and show settings form
  $resizing_enabled = get_option(\'jr_resizeupload_resize_yesno\');
  $force_jpeg_recompression = get_option(\'jr_resizeupload_recompress_yesno\');
  $compression_level  = intval(get_option(\'jr_resizeupload_quality\'));

  $max_width     = get_option(\'jr_resizeupload_width\');
  $max_height    = get_option(\'jr_resizeupload_height\');

  $convert_png_to_jpg = get_option(\'jr_resizeupload_convertpng_yesno\');
  $convert_gif_to_jpg = get_option(\'jr_resizeupload_convertgif_yesno\');
  $convert_bmp_to_jpg = get_option(\'jr_resizeupload_convertbmp_yesno\');
?>
<style type="text/css">
.resizeimage-button {
  color: #FFF;
  background: none repeat scroll 0% 0% #FC9A24;
  border-radius: 3px;
  display: inline-block;
  border-bottom: 4px solid #EC8A14;
  margin-right:5px;
  line-height:1.05em;
  text-align: center;
  text-decoration: none;
  padding: 9px 20px 8px;
  font-size: 15px;
  font-weight: bold;
  text-shadow: 0 -1px 1px rgba(0,0,0,0.2);
}

.resizeimage-button:active,
.resizeimage-button:hover,
.resizeimage-button:focus {
  background-color: #EC8A14;
  color: #FFF;
}

.media-upload-form div.error, .wrap div.error, .wrap div.updated {
  margin: 25px 0px 25px;
}

</style>

<div class="wrap">
    <form method="post" accept-charset="utf-8">

        <h2><img src="<?php echo plugins_url(\'icon-128x128.png\', __FILE__ ); ?>" style="float:right; border:1px solid #ddd;margin:0 0 15px 15px;width:100px; height:100px;" />Resize Image After Upload</h2>

        <div style="max-width:700px">
        <p>This plugin automatically resizes uploaded images (JPEG, GIF, and PNG) to within a given maximum width and/or height to reduce server space usage. This may be necessary due to the fact that images from digital cameras and smartphones can now be over 10MB each due to higher megapixel counts.</p>

        <p>In addition, the plugin can force re-compression of uploaded JPEG images, regardless of whether they are resized or not; and convert uploaded GIF and PNG images into JPEG format.</p>

        <p><strong>Note:</strong> the resizing/recompression process will discard the original uploaded file including EXIF data.</p>

        <p>This plugin is not intended to replace the WordPress <em>add_image_size()</em> function, but rather complement it. Use this plugin to ensure that no excessively large images are stored on your server, then use <em>add_image_size()</em> to create versions of the images suitable for positioning in your website theme.</p>

        <p>This plugin uses standard PHP image resizing functions and will require a high amount of memory (RAM) to be allocated to PHP in your php.ini file (e.g 512MB).</p>

        <h4 style="font-size: 15px;font-weight: bold;margin: 2em 0 0;">Like the plugin?</h4>

        <p>This plugin was written and is maintained for free (as in free beer) by me, <a href="http://philr.ae" target="_blank">Phil Rae</a>. If you find it useful please consider donating some small change or bitcoins to my beer fund because beer is very seldom free. Thanks!</p>

        <p style="padding-bottom:2em;" class="resizeimage-button-wrapper">

          <a class="resizeimage-button" href="https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=3W4M254AA3KZG" target="_blank">Donate cash</a>

        <a class="resizeimage-button coinbase-button" data-code="9584265cb76df0b1e99979163de143f5" data-button-style="custom_small" target="_blank" href="https://coinbase.com/checkouts/9584265cb76df0b1e99979163de143f5">Donate bitcoins</a>

        </p>
        </div>

        <hr style="margin-top:20px; margin-bottom:0;">
        <hr style="margin-top:1px; margin-bottom:40px;">

        <h3>Re-sizing options</h3>
        <table class="form-table">
            <tr>
                <th scope="row">Enable re-sizing</th>
                <td valign="top">
                    <select name="yesno" id="yesno">
                        <option value="no" label="no" <?php echo ($resizing_enabled == \'no\') ? \'selected="selected"\' : \'\'; ?>>NO - do not resize images</option>
                        <option value="yes" label="yes" <?php echo ($resizing_enabled == \'yes\') ? \'selected="selected"\' : \'\'; ?>>YES - resize large images</option>
                    </select>
                </td>
            </tr>

            <tr>
                <th scope="row">Max image dimensions</th>

                <td>
                    <fieldset><legend class="screen-reader-text"><span>Maximum width and height</span></legend>
                        <label for="maxwidth">Max width</label>
                        <input name="maxwidth" step="1" min="0" id="maxwidth" class="small-text" type="number" value="<?php echo $max_width; ?>">
                        &nbsp;&nbsp;&nbsp;<label for="maxheight">Max height</label>
                        <input name="maxheight" step="1" min="0" id="maxheight" class="small-text" type="number" value="<?php echo $max_height; ?>">
                        <p class="description">Set to zero or very high value to prevent resizing in that dimension.
                        <br />Recommended values: <code>1200</code></p>
                    </fieldset>
                </td>


            </tr>

        </table>

        <hr style="margin-top:20px; margin-bottom:30px;">

        <h3>Compression options</h3>
        <p style="max-width:700px">The following settings will only apply to uploaded JPEG images and images converted to JPEG format.</p>

        <table class="form-table">

            <tr>
                <th scope="row">JPEG compression level</th>
                <td valign="top">
                    <select id="quality" name="quality">
                    <?php for($i=1; $i<=100; $i++) : ?>
                        <option value="<?php echo $i; ?>" <?php if($compression_level == $i) : ?>selected<?php endif; ?>><?php echo $i; ?></option>
                    <?php endfor; ?>
                    </select>
                    <p class="description"><code>1</code> = low quality (smallest files)
                    <br><code>100</code> = best quality (largest files)
                    <br>Recommended value: <code>90</code></p>
                </td>
            </tr>

            <tr>
                <th scope="row">Force JPEG re-compression</th>
                <td>
                    <select name="recompress_yesno" id="yesno">
                        <option value="no" label="no" <?php echo ($force_jpeg_recompression == \'no\') ? \'selected="selected"\' : \'\'; ?>>NO - only re-compress resized jpeg images</option>
                        <option value="yes" label="yes" <?php echo ($force_jpeg_recompression == \'yes\') ? \'selected="selected"\' : \'\'; ?>>YES - re-compress all uploaded jpeg images</option>
                    </select>
                </td>
            </tr>

        </table>

        <?php /* DEFINED HERE FOR FUTURE RELEASE - does not do anything if uncommented
        <hr style="margin-top:20px; margin-bottom:20px;">

        <h3>Image conversion options</h3>
        <p style="max-width:700px">Photos saved as PNG and GIF images can be extremely large in file size due to their compression methods not being suited for photos. Enable these options below to automatically convert GIF and/or PNG images to JPEG.</p>

        <p>When enabled, conversion will happen to all uploaded GIF/PNG images, not just ones that require resizing.</p>

        <table class="form-table">

            <tr>
                <th scope="row">Convert GIF to JPEG</th>
                <td>
                    <select id="convert-gif" name="convertgif">
                        <option value="no" <?php if($convert_gif_to_jpg == \'no\') : ?>selected<?php endif; ?>>NO - just resize uploaded gif images as normal</option>
                        <option value="yes" <?php if($convert_gif_to_jpg == \'yes\') : ?>selected<?php endif; ?>>YES - convert all uploaded gif images to jpeg</option>
                    </select>
                </td>
            </tr>

            <tr>
                <th scope="row">Convert PNG to JPEG</th>
                <td>
                    <select id="convert-png" name="convertpng">
                        <option value="no" <?php if($convert_png_to_jpg == \'no\') : ?>selected<?php endif; ?>>NO - just resize uploaded png images as normal</option>
                        <option value="yes" <?php if($convert_png_to_jpg == \'yes\') : ?>selected<?php endif; ?>>YES - convert all uploaded png images to jpeg</option>
                    </select>
                </td>
            </tr>

        </table>
        */ ?>

        <hr style="margin-top:30px;">

        <p class="submit" style="margin-top:10px;border-top:1px solid #eee;padding-top:20px;">
          <input type="hidden" id="convert-bmp" name="convertbmp" value="no" />
          <input type="hidden" name="action" value="update" />
          <input id="submit" name="jr_options_update" class="button button-primary" type="submit" value="Update Options">
        </p>
    </form>

</div>
<?php
} // function jr_uploadresize_options(){





/**
* This function will apply changes to the uploaded file
* @param $image_data - contains file, url, type
*/
function jr_uploadresize_resize($image_data){


  jr_error_log("**-start--resize-image-upload");


  $resizing_enabled = get_option(\'jr_resizeupload_resize_yesno\');
    $resizing_enabled = ($resizing_enabled==\'yes\') ? true : false;

  $force_jpeg_recompression = get_option(\'jr_resizeupload_recompress_yesno\');
    $force_jpeg_recompression = ($force_jpeg_recompression==\'yes\') ? true : false;

  $compression_level = get_option(\'jr_resizeupload_quality\');


  $max_width  = get_option(\'jr_resizeupload_width\')==0 ? false : get_option(\'jr_resizeupload_width\');

  $max_height = get_option(\'jr_resizeupload_height\')==0 ? false : get_option(\'jr_resizeupload_height\');


  $convert_png_to_jpg = get_option(\'jr_resizeupload_convertpng_yesno\');
    $convert_png_to_jpg = ($convert_png_to_jpg==\'yes\') ? true : false;

  $convert_gif_to_jpg = get_option(\'jr_resizeupload_convertgif_yesno\');
    $convert_gif_to_jpg = ($convert_gif_to_jpg==\'yes\') ? true : false;

  $convert_bmp_to_jpg = get_option(\'jr_resizeupload_convertbmp_yesno\');
    $convert_bmp_to_jpg = ($convert_bmp_to_jpg==\'yes\') ? true : false;



  //---------- In with the old v1.6.2, new v1.7 (WP_Image_Editor) ------------

  if($resizing_enabled || $force_jpeg_recompression) {

        $fatal_error_reported = false;
        $valid_types = array(\'image/gif\',\'image/png\',\'image/jpeg\',\'image/jpg\');

    if(empty($image_data[\'file\']) || empty($image_data[\'type\'])) {
        jr_error_log("--non-data-in-file-( ".print_r($image_data, true)." )");  
          $fatal_error_reported = true;
    }
    else if(!in_array($image_data[\'type\'], $valid_types)) {
        jr_error_log("--non-image-type-uploaded-( ".$image_data[\'type\']." )");
          $fatal_error_reported = true;
    }

    jr_error_log("--filename-( ".$image_data[\'file\']." )");
    $image_editor = wp_get_image_editor($image_data[\'file\']);
    $image_type = $image_data[\'type\'];


    if($fatal_error_reported || is_wp_error($image_editor)) {
      jr_error_log("--wp-error-reported");
    }
    else {

      $to_save = false;
      $resized = false;


      // Perform resizing if required
      if($resizing_enabled) {

        jr_error_log("--resizing-enabled");
        $sizes = $image_editor->get_size();

        if((isset($sizes[\'width\']) && $sizes[\'width\'] > $max_width)
          || (isset($sizes[\'height\']) && $sizes[\'height\'] > $max_height)) {

          $image_editor->resize($max_width, $max_height, false);
          $resized = true;
          $to_save = true;

          $sizes = $image_editor->get_size();
          jr_error_log("--new-size--".$sizes[\'width\']."x".$sizes[\'height\']);
        }
        else {
          jr_error_log("--no-resizing-needed");
        }
      }
      else {
        jr_error_log("--no-resizing-requested");
      }


      // Regardless of resizing, image must be saved if recompressing
      if($force_jpeg_recompression && ($image_type==\'image/jpg\' || $image_type==\'image/jpeg\')) {

        $to_save = true;
        jr_error_log("--compression-level--q-".$compression_level);
      }
      elseif(!$resized) {
        jr_error_log("--no-forced-recompression");
      }


      // Only save image if it has been resized or need recompressing
      if($to_save) {

        $image_editor->set_quality($compression_level);
        $saved_image = $image_editor->save($image_data[\'file\']);
        jr_error_log("--image-saved");
      }
      else {
        jr_error_log("--no-changes-to-save");
      }
    }
  } // if($resizing_enabled || $force_jpeg_recompression)

  else {
    jr_error_log("--no-action-required");
  }

  jr_error_log("**-end--resize-image-upload\\n");


  return $image_data;
} // function jr_uploadresize_resize($image_data){


/**
* Simple debug logging function. Will only output to the log file
* if \'debugging\' is turned on.
*/
function jr_error_log($message) {
  global $DEBUG_LOGGER;

  if($DEBUG_LOGGER) {
    error_log(print_r($message, true));
  }
}