Images section (#813)

* Add new configuration options
* Refactor scan/clean
* Schema changes
* Add details to galleries
* Remove redundant code
* Refine thumbnail generation
* Gallery overhaul
* Don't allow modifying zip gallery images
* Show gallery card overlays
* Hide zoom slider when not in grid mode

pkg/image/thumbnail.go

@@ -0,0 +1,40 @@
+package image
+
+import (
+	"bytes"
+	"image"
+	"image/jpeg"
+
+	"github.com/disintegration/imaging"
+)
+
+func ThumbnailNeeded(srcImage image.Image, maxSize int) bool {
+	dim := srcImage.Bounds().Max
+	w := dim.X
+	h := dim.Y
+
+	return w > maxSize || h > maxSize
+}
+
+// GetThumbnail returns the thumbnail image of the provided image resized to
+// the provided max size. It resizes based on the largest X/Y direction.
+// It returns nil and an error if an error occurs reading, decoding or encoding
+// the image.
+func GetThumbnail(srcImage image.Image, maxSize int) ([]byte, error) {
+	var resizedImage image.Image
+
+	// if height is longer then resize by height instead of width
+	dim := srcImage.Bounds().Max
+	if dim.Y > dim.X {
+		resizedImage = imaging.Resize(srcImage, 0, maxSize, imaging.Box)
+	} else {
+		resizedImage = imaging.Resize(srcImage, maxSize, 0, imaging.Box)
+	}
+
+	buf := new(bytes.Buffer)
+	err := jpeg.Encode(buf, resizedImage, nil)
+	if err != nil {
+		return nil, err
+	}
+	return buf.Bytes(), nil
+}