Suffix Image Resizer

Automatically resizes images whose filename ends with a configured string (for example BottleImage.webp). Rules are applied to new uploads as they arrive and can be applied in bulk to images already in the Media Library. Three modes are supported: fit, crop, and pad (centers the image on a fixed-size canvas, transparent where the format allows).

Contents

• How it works
• Installation
• Rule syntax
• Resize modes
• Examples
• Resizing existing images
• Behavior and limits
• Developer reference
• Security
• Troubleshooting

How it works

1. You define one or more rules, one per line, in the settings page.
2. On upload: the wp_handle_upload filter checks each uploaded image's filename against the rules. On a match, the file is resized in place before WordPress generates its thumbnails.
3. On existing images: a button on the settings page scans the Media Library, finds every image whose filename matches a rule, resizes it, deletes its old generated thumbnails, and regenerates the attachment metadata.

If a resize fails on upload, the original upload is left untouched.

Installation

1. Copy suffix-image-resizer.php into wp-content/plugins/suffix-image-resizer/.
2. Activate Suffix Image Resizer in Plugins.
3. Go to Settings → Suffix Image Resizer and review the rules.

A default rule is provided: BottleImage.webp|800|800|pad.

Rule syntax

One rule per line:

suffix|width|height|mode|background

Additional notes:

• Lines that are blank or start with # are ignored.
• The first matching rule wins, in the order listed.
• Rules with an empty suffix, or with both width and height at 0, are skipped.
• crop and pad need both dimensions. If either is 0, the rule silently falls back to fit.
• An unrecognized mode falls back to fit. An invalid background value falls back to transparent.

Resize modes

Pad mode and transparency

Pad rendering uses Imagick when available and falls back to GD. If neither can process the file, an error is returned (and, on upload, the file is left as-is).

Examples

# Square, transparent padding
BottleImage.webp|800|800|pad

# Square, white padding
LabelImage|1000|1000|pad|#ffffff

# Max 1200px wide, any height, keep proportions
-hero.jpg|1200|0|fit

# Center-cropped 16:9 banner
BannerImage|1600|900|crop

Resizing existing images

On the settings page, the Resize existing images section applies the saved rules (save before running) to the Media Library.

• Back up originals (checked by default) copies each file to wp-content/uploads/sir-backups/ before it is modified. Existing backups are never overwritten, so the first original is preserved across repeated runs.
• Images are processed in batches of 3 over AJAX, with a live log showing each result (resized with before → after dimensions, skipped, or failed).
• Images already at the target size are skipped, so the tool is safe to run repeatedly.
• After resizing, previously generated thumbnails are deleted and metadata is regenerated from the new file. The original_image metadata key, if present, is preserved.

Behavior and limits

• Images are never enlarged. In pad mode, a smaller image is centered on the full canvas at its original size, so the canvas reaches the target size but the image itself is not scaled up.
• Files are modified in place. Without the backup option, the original cannot be recovered from the plugin.
• Quality for re-encoded images uses WordPress's wp_editor_set_quality filter (default 82 here).
• The backup directory is not cleaned up automatically.
• Matching is based on the filename only, not on the attachment title or metadata.
• Settings are stored as a single option and are not removed on deactivation or deletion; there is no uninstall.php.

Developer reference

Key methods

Filters used

• wp_editor_set_quality: read to determine output quality when padding.

Security

• Both AJAX endpoints verify the sir_bulk nonce and require manage_options.
• Attachment IDs from the request are cast with absint.
• The rules option is sanitized with sanitize_textarea_field and escaped on output (esc_textarea, esc_attr).
• Log output in the admin script is inserted as text (.text()), not HTML.
• The scan query uses only static, hard-coded SQL with no user input.

Troubleshooting