50 lines (32 loc) · 1.27 KB

WordPress Image Compressor Plugin

Hooking into the Upload Process

add_filter( 'wp_handle_upload', 'mic_compress_uploaded_image' );

Registers our function to run after a file is uploaded.
Gives us a chance to edit/replace the file before WordPress saves it.

Working with File Paths

$upload['file']

Absolute path to uploaded file.
Used for file system operations (open, edit, delete).

pathinfo($file_path, PATHINFO_EXTENSION)

Extracts file extension (jpg, png, etc.).
Helps determine how to handle the image.

GD Library Image Functions

imagecreatefromjpeg() / imagecreatefrompng() / imagecreatefromgif()

Load image from file into PHP memory as a GD image resource.

imagejpeg($image, $file_path, $quality)

Compress and save the image as JPEG.
quality ranges from 0 (worst) to 100 (best).

imagedestroy($image)

Frees up memory used by the image resource.

File Handling

unlink($file_path)

Deletes a file from the server.
Optional: used when converting PNG to JPEG to remove the original.

Updating Return Value to WordPress

$upload['file'] / $upload['url']

Must be updated if filename or extension changes.
WordPress will use the values we return from the filter.