倍率问题和图片问题调整

backend/internal/assets/image_format.go

@@ -0,0 +1,71 @@
+package assets
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"net/http"
+	"path"
+	"strings"
+)
+
+// normalizeImageFile uses the bytes, not a provider URL suffix or an untrusted
+// Content-Type, as evidence of a recognized raster format. It does not decode
+// or transcode the image. Unrecognized data retains its original metadata.
+func normalizeImageFile(name, contentType string, prefix []byte) (string, string) {
+	if len(prefix) > 512 {
+		prefix = prefix[:512]
+	}
+	detected := http.DetectContentType(prefix)
+	var extension string
+	switch detected {
+	case "image/png":
+		extension = ".png"
+	case "image/jpeg":
+		extension = ".jpg"
+	case "image/webp":
+		extension = ".webp"
+	case "image/gif":
+		extension = ".gif"
+	case "image/bmp":
+		extension = ".bmp"
+	case "image/x-icon":
+		extension = ".ico"
+	default:
+		return name, contentType
+	}
+	name = strings.TrimSpace(name)
+	existing := path.Ext(name)
+	lower := strings.ToLower(existing)
+	if lower == extension || detected == "image/jpeg" && (lower == ".jpeg" || lower == ".jpe") {
+		return name, detected
+	}
+	base := strings.TrimSuffix(name, existing)
+	if base == "" || base == "." || base == "/" {
+		base = "image"
+	}
+	return base + extension, detected
+}
+
+// NormalizeImageDownload fixes legacy filenames and response MIME types from
+// a bounded prefix. The returned body streams every original byte, and Close
+// still closes the underlying OSS/local/remote stream. No catalog/object write
+// is performed, including for historical .image objects.
+func NormalizeImageDownload(name string, blob Blob) (string, Blob, error) {
+	if blob.Body == nil {
+		return name, blob, ErrBlobNotFound
+	}
+	reader := bufio.NewReaderSize(blob.Body, 512)
+	prefix, err := reader.Peek(512)
+	if err != nil && !errors.Is(err, io.EOF) {
+		return name, blob, err
+	}
+	name, blob.ContentType = normalizeImageFile(name, blob.ContentType, prefix)
+	blob.Body = &imageReadCloser{Reader: reader, Closer: blob.Body}
+	return name, blob, nil
+}
+
+type imageReadCloser struct {
+	io.Reader
+	io.Closer
+}