Using WordPress ‘image_resize_dimensions’ PHP filter

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The image_resize_dimensions WordPress PHP Filter allows you to override the default behavior of WordPress when resizing image assets, including thumbnail cropping.

Usage

add_filter('image_resize_dimensions', 'your_custom_function', 10, 6);

function your_custom_function($null, $orig_w, $orig_h, $dest_w, $dest_h, $crop) {
    // your custom code here
    return $null;
}

Parameters

  • $null null|mixed – Whether to preempt output of the resize dimensions.
  • $orig_w int – Original width in pixels.
  • $orig_h int – Original height in pixels.
  • $dest_w int – New width in pixels.
  • $dest_h int – New height in pixels.
  • $crop bool|array – Whether to crop the image to specified width and height or resize. An array can specify the positioning of the crop area. Default false.

More information

See WordPress Developer Resources: image_resize_dimensions

Examples

Custom crop positions

Override the default crop position to be centered horizontally and aligned to the top.

add_filter('image_resize_dimensions', 'custom_crop_position', 10, 6);

function custom_crop_position($null, $orig_w, $orig_h, $dest_w, $dest_h, $crop) {
    if (!$crop) {
        return $null;
    }
    $crop_x = round(($orig_w - $dest_w) / 2);
    $crop_y = 0;
    return array(0, 0, $crop_x, $crop_y, $dest_w, $dest_h, $dest_w, $dest_h);
}

Disable cropping

Prevent image cropping when resizing.

add_filter('image_resize_dimensions', 'disable_image_cropping', 10, 6);

function disable_image_cropping($null, $orig_w, $orig_h, $dest_w, $dest_h, $crop) {
    if ($crop) {
        $crop = false;
    }
    return $null;
}

Custom aspect ratio

Maintain a custom aspect ratio when resizing images.

add_filter('image_resize_dimensions', 'custom_aspect_ratio', 10, 6);

function custom_aspect_ratio($null, $orig_w, $orig_h, $dest_w, $dest_h, $crop) {
    $aspect_ratio = 16 / 9;
    $new_height = round($dest_w / $aspect_ratio);
    return array(0, 0, 0, 0, $dest_w, $new_height, $orig_w, $orig_h);
}

Prevent resizing for small images

Disable resizing for images smaller than the desired dimensions.

add_filter('image_resize_dimensions', 'prevent_small_image_resize', 10, 6);

function prevent_small_image_resize($null, $orig_w, $orig_h, $dest_w, $dest_h, $crop) {
    if ($orig_w < $dest_w && $orig_h < $dest_h) {
        return false;
    }
    return $null;
}

Add a custom resizing method

Create a custom resizing method for images with a specific aspect ratio.

add_filter('image_resize_dimensions', 'custom_resizing_method', 10, 6);

function custom_resizing_method($null, $orig_w, $orig_h, $dest_w, $dest_h, $crop) {
    $aspect_ratio = $orig_w / $orig_h;
    if ($aspect_ratio == 2){ 
        // Perform custom resizing for images with an aspect ratio of 2 
        $new_width = $dest_w; 
        $new_height = round($new_width / 2); 
        $crop_x = round(($orig_w - $new_width) / 2); 
        $crop_y = round(($orig_h - $new_height) / 2); 
        return array(0, 0, $crop_x, $crop_y, $new_width, $new_height, $new_width, $new_height); 
    } 
    // For other aspect ratios, use the default behavior 
    return $null; 
}