2 files changed, 124 insertions, 0 deletions
diff --git a/internal/media/process.go b/internal/media/process.go
new file mode 100644
index 0000000..bb3ac89
--- /dev/null
+++ b/internal/media/process.go
@@ -0,0 +1,46 @@
+package media
+
+import (
+	"fmt"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+// 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) {
+	if format != "webp" && format != "jpeg" {
+		return nil, fmt.Errorf("unsupported format %q: must be webp or jpeg", format)
+	}
+
+	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
+	}
+	return nil, fmt.Errorf("unsupported format %q", format)
+}
diff --git a/internal/media/process_test.go b/internal/media/process_test.go
new file mode 100644
index 0000000..da9d4a8
--- /dev/null
+++ b/internal/media/process_test.go
@@ -0,0 +1,78 @@
+package media
+
+import (
+	"image"
+	"image/png"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+func TestMain(m *testing.M) {
+	vips.Startup(nil)
+	code := m.Run()
+	vips.Shutdown()
+	os.Exit(code)
+}
+
+// testPNG writes a 100×60 PNG to a temp file and returns its path.
+func testPNG(t *testing.T) string {
+	t.Helper()
+	img := image.NewRGBA(image.Rect(0, 0, 100, 60))
+	path := filepath.Join(t.TempDir(), "src.png")
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatalf("create test png: %v", err)
+	}
+	if err := png.Encode(f, img); err != nil {
+		t.Fatalf("encode test png: %v", err)
+	}
+	f.Close()
+	return path
+}
+
+func TestConvertToWebP(t *testing.T) {
+	out, err := ConvertAndResize(testPNG(t), 0, "webp")
+	if err != nil {
+		t.Fatalf("ConvertAndResize: %v", err)
+	}
+	if len(out) == 0 {
+		t.Fatal("expected non-empty output")
+	}
+}
+
+func TestConvertToJPEG(t *testing.T) {
+	out, err := ConvertAndResize(testPNG(t), 0, "jpeg")
+	if err != nil {
+		t.Fatalf("ConvertAndResize: %v", err)
+	}
+	if len(out) == 0 {
+		t.Fatal("expected non-empty output")
+	}
+}
+
+func TestResizeAndConvert(t *testing.T) {
+	out, err := ConvertAndResize(testPNG(t), 50, "webp")
+	if err != nil {
+		t.Fatalf("ConvertAndResize resize: %v", err)
+	}
+	if len(out) == 0 {
+		t.Fatal("expected non-empty output")
+	}
+}
+
+func TestConvertUnsupportedFormat(t *testing.T) {
+	_, err := ConvertAndResize(testPNG(t), 0, "avif")
+	if err == nil {
+		t.Fatal("expected error for unsupported format")
+	}
+}
+
+func TestConvertMissingFile(t *testing.T) {
+	_, err := ConvertAndResize("/nonexistent/file.png", 0, "webp")
+	if err == nil {
+		t.Fatal("expected error for missing file")
+	}
+}