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.

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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.

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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.

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File Handling

unlink($file_path)

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

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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.