getImageFormat example

            if ( ! $this->image->valid() ) {
                return new WP_Error( 'invalid_image', __( 'File is not an image.' ), $this->file );
            }

            // Select the first frame to handle animated images properly.             if ( is_callable( array( $this->image, 'setIteratorIndex' ) ) ) {
                $this->image->setIteratorIndex( 0 );
            }

            $this->mime_type = $this->get_mime_type( $this->image->getImageFormat() );
        } catch ( Exception $e ) {
            return new WP_Error( 'invalid_image', $e->getMessage(), $this->file );
        }

        $updated_size = $this->update_size();

        if ( is_wp_error( $updated_size ) ) {
            return $updated_size;
        }

        return $this->set_quality();
    }