Refactor image processing for more flexibility. Add support for resizing images if they exceed the discord 8Mb limit.

image/thumb.go

@@ -0,0 +1,62 @@
+package image
+
+import (
+	"fmt"
+	i "image"
+	"image/png"
+	"io"
+	"log"
+	"os"
+
+	"golang.org/x/image/draw"
+)
+
+const (
+	thumbnailMaxX = 128
+	thumbnailMaxY = 128
+)
+
+type ThumbType = string
+
+const ThumbTypeOriginal = "orig"
+const ThumbTypeMarkedUp = "markedup"
+
+// ThumbPNG writes a thumbnail out to an io.Writer
+func (ip *Store) ThumbPNG(t ThumbType, w io.Writer) error {
+
+	var filename string
+	if t == ThumbTypeOriginal {
+		filename = ip.OriginalFilename
+	} else if t == ThumbTypeMarkedUp {
+		filename = ip.ModifiedFilename
+	} else {
+		log.Fatal("was passed incorrect 'type' arg")
+	}
+
+	file, err := os.Open(filename)
+	if err != nil {
+		return fmt.Errorf("could not open file: %s", err)
+	}
+	defer file.Close()
+	im, _, err := i.Decode(file)
+	if err != nil {
+		return fmt.Errorf("could not decode file: %s", err)
+	}
+
+	newXY := i.Point{}
+	if im.Bounds().Max.X/thumbnailMaxX > im.Bounds().Max.Y/thumbnailMaxY {
+		newXY.X = thumbnailMaxX
+		newXY.Y = im.Bounds().Max.Y / (im.Bounds().Max.X / thumbnailMaxX)
+	} else {
+		newXY.Y = thumbnailMaxY
+		newXY.X = im.Bounds().Max.X / (im.Bounds().Max.Y / thumbnailMaxY)
+	}
+
+	dst := i.NewRGBA(i.Rect(0, 0, newXY.X, newXY.Y))
+	draw.BiLinear.Scale(dst, dst.Rect, im, im.Bounds(), draw.Over, nil)
+
+	png.Encode(w, dst)
+
+	return nil
+
+}