You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rotate.go
    path of file: ./repos/imageserver/image/gift
    
    the code of the file until where you have to start completion: package gift

import (
	"fmt"
	"image"
	"image/color"
	"math"

	"github.com/disintegration/gift"
	"github.com/pierrre/imageserver"
	imageserver_image_internal "github.com/pierrre/imageserver/image/internal"
)

const (
	rotateParam = "gift_rot
    
func (prc *RotateProcessor) getFilter(rot float32, params imageserver.Params) (gift.Filter, error) {
	switch rot {
	case 90:
		return gift.Rotate90(), nil
	case 180:
		return gift.Rotate180(), nil
	case 270:
		return gift.Rotate270(), nil
	}
	bkg, err := prc.getBackground(params)
	if err != nil {
		return nil, err
	}
	interp, err := prc.getInterpolation(params)
	if err != nil {
		return nil, err
	}
	return gift.Rotate(rot, bkg, interp), nil
}