1 files changed, 82 insertions, 0 deletions
diff --git a/internal/media/process.go b/internal/media/process.go
new file mode 100644
index 0000000..b295380
--- /dev/null
+++ b/internal/media/process.go
@@ -0,0 +1,82 @@
+package media
+
+import (
+	"bytes"
+	"encoding/base64"
+	"fmt"
+	"image/png"
+
+	"github.com/davidbyttow/govips/v2/vips"
+	thumbhash "go.n16f.net/thumbhash"
+)
+
+// ImageInfo returns the pixel dimensions and a base64-encoded thumbhash for
+// the image at path. The thumbhash is generated from a ≤100px thumbnail so
+// it is fast regardless of the original size.
+func ImageInfo(path string) (width, height int, thumbhashB64 string, err error) {
+	img, err := vips.NewImageFromFile(path)
+	if err != nil {
+		return 0, 0, "", fmt.Errorf("load %s: %w", path, err)
+	}
+	defer img.Close()
+
+	width = img.Width()
+	height = img.Height()
+
+	const maxThumbDim = 100
+	if width > maxThumbDim || height > maxThumbDim {
+		scale := float64(maxThumbDim) / float64(max(width, height))
+		if err := img.Resize(scale, vips.KernelLanczos3); err != nil {
+			return width, height, "", fmt.Errorf("resize for thumbhash: %w", err)
+		}
+	}
+
+	pngBytes, _, err := img.ExportPng(vips.NewPngExportParams())
+	if err != nil {
+		return width, height, "", fmt.Errorf("export png for thumbhash: %w", err)
+	}
+
+	goImg, err := png.Decode(bytes.NewReader(pngBytes))
+	if err != nil {
+		return width, height, "", fmt.Errorf("decode png for thumbhash: %w", err)
+	}
+
+	hash := thumbhash.EncodeImage(goImg)
+	return width, height, base64.StdEncoding.EncodeToString(hash), nil
+}
+
+// ConvertAndResize loads the image at src, optionally resizes it to width pixels
+// wide (maintaining aspect ratio), and exports it in the requested format.
+//
+// width <= 0 means no resize. format must be "webp" or "jpeg".
+func ConvertAndResize(src string, width int, format string) ([]byte, error) {
+	img, err := vips.NewImageFromFile(src)
+	if err != nil {
+		return nil, fmt.Errorf("load image %s: %w", src, err)
+	}
+	defer img.Close()
+
+	if width > 0 && width < img.Width() {
+		scale := float64(width) / float64(img.Width())
+		if err := img.Resize(scale, vips.KernelLanczos3); err != nil {
+			return nil, fmt.Errorf("resize: %w", err)
+		}
+	}
+
+	switch format {
+	case "webp":
+		buf, _, err := img.ExportWebp(vips.NewWebpExportParams())
+		if err != nil {
+			return nil, fmt.Errorf("export webp: %w", err)
+		}
+		return buf, nil
+	case "jpeg":
+		buf, _, err := img.ExportJpeg(vips.NewJpegExportParams())
+		if err != nil {
+			return nil, fmt.Errorf("export jpeg: %w", err)
+		}
+		return buf, nil
+	default:
+		return nil, fmt.Errorf("unsupported format %q: must be webp or jpeg", format)
+	}
+}