added image diff hash distance caching to not overwrite similar images

image.go

@@ -0,0 +1,136 @@
+/*
+Copyright © 2023-2024 Thomas von Dein
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package main
+
+import (
+	"bytes"
+	"image/jpeg"
+	"log/slog"
+	"os"
+	"path/filepath"
+
+	"github.com/corona10/goimagehash"
+)
+
+const MaxDistance = 3
+
+type Image struct {
+	Filename string
+	Hash     *goimagehash.ImageHash
+	Data     *bytes.Buffer
+	Uri      string
+}
+
+// used for logging to avoid printing Data
+func (img *Image) LogValue() slog.Value {
+	return slog.GroupValue(
+		slog.String("filename", img.Filename),
+		slog.String("uri", img.Uri),
+		slog.String("hash", img.Hash.ToString()),
+	)
+}
+
+// holds all images of an ad
+type Images []*Image
+
+func NewImage(buf *bytes.Buffer, filename string, uri string) *Image {
+	img := &Image{
+		Filename: filename,
+		Uri:      uri,
+		Data:     buf,
+	}
+
+	return img
+}
+
+// Calculate diff hash of the image
+func (img *Image) CalcHash() error {
+	jpgdata, err := jpeg.Decode(img.Data)
+	if err != nil {
+		return err
+	}
+
+	hash1, err := goimagehash.DifferenceHash(jpgdata)
+	if err != nil {
+		return err
+	}
+
+	img.Hash = hash1
+
+	return nil
+}
+
+// checks if 2 images are similar enough to be considered the same
+func (img *Image) Similar(otherimg *Image) bool {
+	distance, err := img.Hash.Distance(otherimg.Hash)
+	if err != nil {
+		slog.Debug("failed to compute diff hash distance", "error", err)
+		return false
+	}
+
+	if distance < MaxDistance {
+		slog.Debug("distance computation", "image-A", img, "image-B", otherimg, "distance", distance)
+		return true
+	} else {
+		return false
+	}
+}
+
+// check current image against all known hashes.
+func (img *Image) SimilarExists(images Images) bool {
+	for _, otherimg := range images {
+		if img.Similar(otherimg) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// read all  JPG images  in a  ad directory,  compute diff  hashes and
+// store the results in the slice Images
+func ReadImages(addir string) (Images, error) {
+	files, err := os.ReadDir(addir)
+	if err != nil {
+		return nil, err
+	}
+
+	imgs := Images{}
+
+	for _, file := range files {
+		ext := filepath.Ext(file.Name())
+		if !file.IsDir() && (ext == ".jpg" || ext == ".jpeg" || ext == ".JPG" || ext == ".JPEG") {
+			filename := filepath.Join(addir, file.Name())
+			data, err := ReadImage(filename)
+			if err != nil {
+				return nil, err
+			}
+
+			img := NewImage(data, filename, "")
+			if err = img.CalcHash(); err != nil {
+				return nil, err
+			}
+
+			slog.Debug("Caching image from file system", "image", img, "hash", img.Hash.ToString())
+			imgs = append(imgs, img)
+		}
+	}
+
+	//return nil, errors.New("ende")
+	return imgs, nil
+}