hugo/resources/smartcrop.go

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// Copyright 2019 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 resources
import (
"image"
"github.com/disintegration/imaging"
"github.com/muesli/smartcrop"
)
const (
// Do not change.
smartCropIdentifier = "smart"
// This is just a increment, starting on 1. If Smart Crop improves its cropping, we
// need a way to trigger a re-generation of the crops in the wild, so increment this.
smartCropVersionNumber = 1
)
// Needed by smartcrop
type imagingResizer struct {
filter imaging.ResampleFilter
}
func (r imagingResizer) Resize(img image.Image, width, height uint) image.Image {
return imaging.Resize(img, int(width), int(height), r.filter)
}
func newSmartCropAnalyzer(filter imaging.ResampleFilter) smartcrop.Analyzer {
return smartcrop.NewAnalyzer(imagingResizer{filter: filter})
}
func smartCrop(img image.Image, width, height int, anchor imaging.Anchor, filter imaging.ResampleFilter) (*image.NRGBA, error) {
if width <= 0 || height <= 0 {
return &image.NRGBA{}, nil
}
srcBounds := img.Bounds()
srcW := srcBounds.Dx()
srcH := srcBounds.Dy()
if srcW <= 0 || srcH <= 0 {
return &image.NRGBA{}, nil
}
if srcW == width && srcH == height {
return imaging.Clone(img), nil
}
smart := newSmartCropAnalyzer(filter)
rect, err := smart.FindBestCrop(img, width, height)
if err != nil {
return nil, err
}
b := img.Bounds().Intersect(rect)
cropped := imaging.Crop(img, b)
return imaging.Resize(cropped, width, height, filter), nil
}