3

I know that I can use the jpeg_quality filter like this:

add_filter('jpeg_quality', function($arg){return 75;});

This will reduce the image quality of the images generated during the upload process such as the thumbnail, medium and large image sizes, however the original image is still at the original quailty.

Is there a filter or function I can add that will decrease the image quality of the original image when it's uploaded?

5

In general I wouldn't recommend modifying the original uploaded image files, just in case we might need to re-generate intermediate sizes.

But let's see if it's possible :-)

We can in general let WordPress choose the image editor, that depends on modules like GD or Imagick, through:

$editor = wp_get_image_editor( $file );

but this can return an WP_Error object, so we better check it with is_wp_error( $editor ) before using it.

It's useful to let the image editor handle things through methods like set_quality() and save(). We can see such an usage example in the Resize Image After Upload plugin, mentioned by @MerchantWeb. This is also used by the core in various ways.

The plugin hooks into the wp_handle_upload filter to modify the original uploaded jpeg image files, as far as I understand it.

A) We could therefore use something like the following, to modify the quality of the original jpeg image file (to e.g. 90) during uploads:

/**
 * 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;
} );

but it looks to me that this will also affect all the intermediate sizes, because this runs before they are generated.

B) If we take a look at the media_handle_upload() function, we might consider hooking into the wp_generate_attachment_metadata filter instead, to modify the original jpeg image file, after the intermediate sizes have been generated.

Here's an example (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 );

If we needed to restrict this further, we might wrap this into the wp_handle_upload hook as well and check for the relevant action context, like wp_handle_upload or sideload.

We might also need to set the quality very low while testing, just to see if it worked ;-)

Note: These are only demos, that would need further testing.

Update: Just did some simple testing with an image of our kitchen wall clock. Here we can see that when the full size image is re-saved, with quality 5, then all the intermediate sizes:

  • A) are also at low quality.
  • B) are not affected.

Here are the combined results:

a

b

0

This answer could help you: https://wordpress.stackexchange.com/a/69287/92649

You would need to upload your image at a higher resolution than "large" to have that effect, though

0

There is a plugin called Resize Image After Upload:

<?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));
  }
}
  • We'd prefer that answers give a substantive code-based solution to the question rather than simply refer to a plugin. That way we can all learn to write better code. This is about WP Development. The question asks if you know of a filter or function, not a plugin. – Caspar Apr 22 '16 at 20:29
  • look at function jr_uploadresize_options(){ I believe his plugin is using the functions sought after. I know it's not a perfectly deduced answer yet but I just wanted to put this out there in case it helped speed things along.... If I waited till I had th eperfect answer I might never give one. I guess that is preferred? – MerchantWeb Apr 22 '16 at 20:34
  • @MerchantWeb Please reduce the code to the absolute necessary minimum, and explain the key parts in plain English. Just code blocks or just links are not good answers. – fuxia Apr 22 '16 at 22:43
  • Nonetheless, @birgire expanded on it as I was hoping someone would so kudos to him for helping clear it up. I didn't know how to but knew it was a start. For what it is worth and I hope the OP sees this, I would not use Wordpress at all to do this. I would run an action in photoshop on all the files before uploading them to reduce the size to whatever I want. Record the action of changing the image size and saving for web on one of the files. Then apply that action to all the files in a folder. This will give overall smaller file sizes on your server and maintain high quality. – MerchantWeb Apr 23 '16 at 17:48

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