Initial orientator

internal/pipeline/imgrot.go

@@ -0,0 +1,80 @@
+package pipeline
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/jpeg"
+	"image/png"
+	"strings"
+
+	"golang.org/x/image/tiff"
+	_ "golang.org/x/image/webp" // decode-only; we re-encode webp as png
+)
+
+// RotateImage rotates src clockwise by angle (must be 0/90/180/270).
+func RotateImage(src image.Image, angle int) image.Image {
+	angle = ((angle % 360) + 360) % 360
+	if angle == 0 {
+		return src
+	}
+	b := src.Bounds()
+	w, h := b.Dx(), b.Dy()
+	switch angle {
+	case 180:
+		dst := image.NewRGBA(image.Rect(0, 0, w, h))
+		for y := 0; y < h; y++ {
+			for x := 0; x < w; x++ {
+				dst.Set(w-1-x, h-1-y, src.At(b.Min.X+x, b.Min.Y+y))
+			}
+		}
+		return dst
+	case 90:
+		dst := image.NewRGBA(image.Rect(0, 0, h, w))
+		for y := 0; y < h; y++ {
+			for x := 0; x < w; x++ {
+				dst.Set(h-1-y, x, src.At(b.Min.X+x, b.Min.Y+y))
+			}
+		}
+		return dst
+	case 270:
+		dst := image.NewRGBA(image.Rect(0, 0, h, w))
+		for y := 0; y < h; y++ {
+			for x := 0; x < w; x++ {
+				dst.Set(y, w-1-x, src.At(b.Min.X+x, b.Min.Y+y))
+			}
+		}
+		return dst
+	}
+	return src
+}
+
+// EncodeImage re-encodes img using format hint from the original filename / detected format.
+// Falls back to PNG when format is not directly writable.
+func EncodeImage(img image.Image, format string) ([]byte, string, error) {
+	var buf bytes.Buffer
+	switch strings.ToLower(format) {
+	case "jpeg", "jpg":
+		if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 92}); err != nil {
+			return nil, "", err
+		}
+		return buf.Bytes(), "jpg", nil
+	case "tiff", "tif":
+		if err := tiff.Encode(&buf, img, &tiff.Options{Compression: tiff.Deflate}); err != nil {
+			return nil, "", err
+		}
+		return buf.Bytes(), "tiff", nil
+	case "png", "":
+		if err := png.Encode(&buf, img); err != nil {
+			return nil, "", err
+		}
+		return buf.Bytes(), "png", nil
+	case "webp":
+		// Re-encode to PNG (no webp encoder in stdlib/x/image).
+		if err := png.Encode(&buf, img); err != nil {
+			return nil, "", err
+		}
+		return buf.Bytes(), "png", nil
+	}
+	return nil, "", fmt.Errorf("unsupported format: %s", format)
+}