code: // Copyright 2020 The Hugo Authors. All rights reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  // http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  package images
  
  import (
  	"fmt"
  	"image"
  	"image/draw"
  
  	"github.com/disintegration/gift"
  )
  
  var _ gift.Filter = (*overlayFilter)(nil)
  
  type overlayFilter struct {
  	src  ImageSource
  	x, y int
  }
  
  func (f overlayFilter) Draw(dst draw.Image, src image.Image, options *gift.Options) {
  	overlaySrc, err := f.src.DecodeImage()
  	if err != nil {
  		panic(fmt.Sprintf("failed to decode image: %s", err))
  	}
  
  	gift.New().Draw(dst, src)
  	gift.New().DrawAt(dst, overlaySrc, image.Pt(f.x, f.y), gift.OverOperator)
  }
  
  func (f overlayFilter) Bounds(srcBounds image.Rectangle) image.Rectangle {
  	return image.Rect(0, 0, srcBounds.Dx(), srcBounds.Dy())
  }
  