From 67d55d873e366baedfdf987f4be14ef6d7fd2d79 Mon Sep 17 00:00:00 2001
From: Spiegel <spiegel.im.spiegel@gmail.com>
Date: Tue, 12 May 2026 17:14:07 +0900
Subject: [PATCH] feat: add ImageBytes API for in-memory image download

---
 README.md       |  8 ++++++++
 webinfo.go      | 45 +++++++++++++++++++++++++++++++++++++++++++++
 webinfo_test.go | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 88 insertions(+)

diff --git a/README.md b/README.md
index 739741a..ab840e6 100644
--- a/README.md
+++ b/README.md
@@ -76,11 +76,18 @@ thumbPath, err := info.DownloadThumbnail(ctx, "thumbnails", 150, false)
 if err != nil {
   return err
 }
+
+imgBytes, err := info.ImageBytes(ctx)
+if err != nil {
+  return err
+}
+fmt.Println(len(imgBytes))
 ```
 
 ### Public API
 
 - `Fetch(ctx, rawURL, userAgent)` extracts metadata from a page.
+- `(*Webinfo).ImageBytes(ctx)` downloads `Webinfo.ImageURL` into memory.
 - `(*Webinfo).DownloadImage(ctx, destDir, temporary)` downloads `Webinfo.ImageURL`.
 - `(*Webinfo).DownloadThumbnail(ctx, destDir, width, temporary)` creates a resized thumbnail.
 
@@ -96,6 +103,7 @@ if err != nil {
   3. sniff first 512 bytes (`http.DetectContentType`)
   4. fallback `.img`
 - `DownloadThumbnail` uses width `150` when `width <= 0`.
+- `ImageBytes` reads the full response body into memory; very large images can increase memory usage.
 
 ## Error handling
 
diff --git a/webinfo.go b/webinfo.go
index ba9feae..0892c60 100644
--- a/webinfo.go
+++ b/webinfo.go
@@ -34,6 +34,51 @@ type Webinfo struct {
 	UserAgent   string `json:"user_agent,omitempty"`  // User-Agent used to fetch the page
 }
 
+// ImageBytes downloads w.ImageURL and returns its contents in memory.
+//
+// Risk: this method reads the entire response body into memory, so very large
+// images can increase memory usage.
+//
+// Returned errors are wrapped with context and include response close failures.
+func (w *Webinfo) ImageBytes(ctx context.Context) (data []byte, err error) {
+	if w == nil {
+		err = errs.Wrap(ErrNullPointer)
+		return
+	}
+	if w.ImageURL == "" {
+		err = errs.Wrap(ErrNoImageURL)
+		return
+	}
+
+	parsed, uerr := fetch.URL(strings.TrimSpace(w.ImageURL))
+	if uerr != nil {
+		err = errs.Wrap(uerr, errs.WithContext("url", w.ImageURL))
+		return
+	}
+
+	resp, ferr := fetch.New(fetch.WithHTTPClient(newHTTPClient())).GetWithContext(
+		ctx,
+		parsed,
+		fetch.WithRequestHeaderSet("User-Agent", getUserAgent(w.UserAgent)),
+	)
+	if ferr != nil {
+		err = errs.Wrap(ferr, errs.WithContext("url", parsed.String()))
+		return
+	}
+	defer func() {
+		if cerr := resp.Close(); cerr != nil && cerr != os.ErrClosed {
+			err = errs.Join(cerr, err)
+		}
+	}()
+
+	data, err = io.ReadAll(resp.Body())
+	if err != nil {
+		err = errs.Wrap(err, errs.WithContext("url", parsed.String()))
+		return
+	}
+	return
+}
+
 // DownloadImage downloads w.ImageURL and writes it under destDir.
 //
 // If temporary is true, or if the URL path has no filename, a temporary file is created.
diff --git a/webinfo_test.go b/webinfo_test.go
index 241759b..78ed2af 100644
--- a/webinfo_test.go
+++ b/webinfo_test.go
@@ -142,6 +142,41 @@ func TestDownloadImage_NilReceiver(t *testing.T) {
 	}
 }
 
+func TestImageBytes_NilReceiver(t *testing.T) {
+	var w *Webinfo
+	_, err := w.ImageBytes(context.Background())
+	if err == nil {
+		t.Fatalf("expected error for nil receiver")
+	}
+}
+
+func TestImageBytes_EmptyURL(t *testing.T) {
+	w := &Webinfo{}
+	_, err := w.ImageBytes(context.Background())
+	if err == nil {
+		t.Fatalf("expected error for empty image URL")
+	}
+}
+
+func TestImageBytes_Success(t *testing.T) {
+	body := makeImageBytes(10, 10, "png", 0xaa, 0xbb, 0xcc)
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "image/png")
+		_, _ = w.Write(body)
+	})
+	srv := httptest.NewServer(handler)
+	defer srv.Close()
+
+	w := &Webinfo{ImageURL: srv.URL + "/img.png"}
+	got, err := w.ImageBytes(context.Background())
+	if err != nil {
+		t.Fatalf("ImageBytes failed: %v", err)
+	}
+	if !bytes.Equal(got, body) {
+		t.Fatalf("ImageBytes content mismatch")
+	}
+}
+
 func TestDownloadImage_SaveWithFilename(t *testing.T) {
 	// serve a PNG at /images/pic.png
 	handler := func(wr http.ResponseWriter, r *http.Request) {