My current theme uses custom field for image thumbnails (custom field key is 'image'). Now I want to start using new theme which supports wordpress' featured image feature as the theme supports version 2.9+.
I want to migrate all the custom field images to featured image and resize them to new thumbnail sizes as per the new theme requirement.
I tried using "Regenerate Thumbnails" plugin but it resizes all the images attached to all the posts. I just want to resize featured images to new thumbnail size.
So basically I want,
1) Convert custom field image to featured image.
2) Resize all the featured images to new dimensions.