How to scale up featured post thumbnail?

The situation is this: I’m using Video Thumbnails plugin to automatically get and set youtube/vimeo thumbnails as post featured image. The problem is that default youtube/vimeo thumbnail sizes are just a bit smaller than my theme main content width.

So what I need is to scale them up. If I go to the Media Library, I can edit each image manually, then set my exact width and WordPress scales it up just right (I dont mind that the quality is a bit worse). So is there a way that WP would do that automatically each time an image is uploaded?

This is my defined image size: add_image_size('post-full', 688, 320, true); Vimeo thumb size is 640×320.

Answers:

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Method 1

You can use the native WordPress image_resize function to scale up images. WordPress provides a hook called “image_resize_dimensions” which you can use to overwrite the default cropping settings. Here is a modified function which will support scaling up:

function image_crop_dimensions($default, $orig_w, $orig_h, $new_w, $new_h, $crop){
    if ( !$crop ) return null; // let the wordpress default function handle this

    $aspect_ratio = $orig_w / $orig_h;
    $size_ratio = max($new_w / $orig_w, $new_h / $orig_h);

    $crop_w = round($new_w / $size_ratio);
    $crop_h = round($new_h / $size_ratio);

    $s_x = floor( ($orig_w - $crop_w) / 2 );
    $s_y = floor( ($orig_h - $crop_h) / 2 );

    return array( 0, 0, (int) $s_x, (int) $s_y, (int) $new_w, (int) $new_h, (int) $crop_w, (int) $crop_h );
}

Now hook this function like so:

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

Once thats done, you can use the image_resize function to scale images up or down as required.

$cropped_image = image_resize($image_filepath, $width, $height, true);

Method 2

the easiest way would be to add an image-size with 640×298, and use css to resize it. as it is just a minor scale up, the browser scaling should work quite fine.

unfortunately, all the plugins i know do not provide image upscaling, just generating of the smaller image sizes, so if you want to have the 688×320 on your server, you would have to edit one of the existing plugins.

if you have Imagick installed, you can alter your plugin in file video-thumbnails.php on line 325, generating a larger version of the thumbnail, using this code:

$image_big = new Imagick();
$image_big->setOption('jpeg:size', '688x344');
$image_big->readImage($new_thumbnail);

$upload = wp_upload_bits( basename( $new_thumbnail ), null, $image_big );

and let wordpress generate the smaller thumbnail from it (cutting the height). Be sure to make different Imagesizes for the different Videoplatforms in your Imagick Code!

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0