I was looking for the same thing and tried the example above, was the good way but no so simple for me, finally it done this :
1 : create the checkbox field with the different size
(thumbnail : thumbnail
medium : medium
large : large
full : full
custom-size : custom-size)
2 : the code to display
<?php
$attachment_id = get_field('image');
$field = get_field_object('size');
$value = get_field('size');
$label = $field['choices'][ $value ];
$image = wp_get_attachment_image_src( $attachment_id, $label );
// url = $image[0];
// width = $image[1];
// height = $image[2];
?>
<a href="<?php echo $image[0]; ?>" class="fancybox"><img src="<?php echo $image[0]; ?>" /></a>
It works good and the check box very easy to use !
Now have to find a solution to the Gallery field…
We really need this feature, without all the pictures are full size !! it looks a detail but when you have a lot of pictures to manage you understand how important it is. Many Thanks ! ACF is great !
