morganestes
9/12/2018 - 4:56 PM

Regenerate image sizes for specific posts

Regenerate image sizes for specific posts

README.md
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Regenerate specific image size for a post type

Background

I have a custom post type called lfh_home, which uses an image size called card-header on post listing pages.

When I make changes to that image size for testing, I want to regenerate the thumbnails/generated media, but don't want to do it to all 3000+ images on the site.

The goal here is to get the posts of the lfh_home post type, get the ID of the featured image (stored in the _thumbnail_id post meta field), and regenerate just the card-header image.

A regular wp media regenerate --image_size=card-header task takes approximately 12m24s to process 2971 images in local testing. This script takes 44s to process 10 images on the same machine.

Usage

  1. Put the script into a directory you can run commands from using WP-CLI.
  2. Make the script executable with chmod +x regenerate-images-for-post-type.sh
  3. Run ./regenerate-images-for-post-type.sh <post_type> <image_size>, where post_type is your post type (default 'post') and image_size is an image size registered with WordPress (default 'thumbnail').
regenerate-images-for-post-type.sh
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#!/usr/bin/env bash

wproot() {
	wp --allow-root "$@"
}

wp_regenerate_thumbnails() {
  declare -a thumbnail_ids

  local post_type=${1:-post}
  local image_size=${2:-thumbnail}
  local thumbnail_id

  printf "Getting images to regenerate...\\n\\n"

  for post_id in $(wproot post list --post_type="${post_type}" --field=ID); do
    thumbnail_id="$(wproot post meta get "${post_id}" _thumbnail_id)"

    if [[ -n "${thumbnail_id}" ]]; then
        thumbnail_ids+=("${thumbnail_id}")
    fi
  done

  printf "Regenerating %d \"%s\" images for \"%s\" posts...\\n\\n" ${#thumbnail_ids[@]} "${image_size}" "${post_type}"

  for image_id in "${thumbnail_ids[@]}"; do
    wproot media regenerate "${image_id}" --image_size="${image_size}"
  done

  printf "Done regenerating images for \"%s\".\\n\\n" "${post_type}"
}

wp_regenerate_thumbnails "$1" "$2"