Reinstating special treatment of string arguments to analyzeHeader(),…

… but now explicitly ignoring internal images

R/nifti.R

@@ -218,6 +218,14 @@ updateNifti <- function (image, template = NULL, datatype = "auto")
 #'   ANALYZE \code{originator} field to store a coordinate origin. This
 #'   interpretation is also returned, in the \code{origin} field.
 #' 
+#'   Both of these functions call \code{\link{asNifti}} on their arguments to
+#'   coerce it to NIfTI, except in one specific circumstance: when
+#'   \code{analyzeHeader} is called with a single-element character-mode
+#'   argument that is not an \code{"internalImage"} object. In this case the
+#'   string is taken to be a path and the header is reported as stored on disk.
+#'   This is because otherwise the header may be changed by the process of
+#'   converting it to NIfTI and back.
+#' 
 #' @examples
 #' niftiHeader(system.file("extdata", "example.nii.gz", package="RNifti"))
 #' 
@@ -238,7 +246,11 @@ niftiHeader <- dumpNifti <- function (image = list())
 #' @export
 analyzeHeader <- function (image = list())
 {
-    .Call("analyzeHeader", asNifti(image,internal=TRUE), PACKAGE="RNifti")
+    # Special case needed to avoid converting to NIfTI internally first
+    if (is.character(image) && length(image) == 1 && !inherits(image,"internalImage"))
+        .Call("analyzeHeader", image, PACKAGE="RNifti")
+    else
+        .Call("analyzeHeader", asNifti(image,internal=TRUE), PACKAGE="RNifti")
 }
 
 #' @rdname niftiHeader

src/main.cpp

@@ -281,12 +281,32 @@ END_RCPP
 RcppExport SEXP analyzeHeader (SEXP _image)
 {
 BEGIN_RCPP
-    const NiftiImage image(_image, false, true);
-    if (image.isNull())
-        return R_NilValue;
-
+    RObject object(_image);
     nifti_1_header header;
-    nifti_convert_nim2n1hdr(image, &header);
+
+    // This special-case treatment of strings is important, because converting
+    // ANALYZE files into NIfTI objects and back is somewhat destructive. It
+    // mustn't pick up internal images by accident, though
+    if (Rf_isString(object) && !object.hasAttribute(".nifti_image_ptr"))
+    {
+        const std::string path = as<std::string>(object);
+        int version;
+        void *ptr = nifti2_read_header(RNifti::internal::stringToPath(path), &version, true);
+        if (ptr == NULL)
+            return R_NilValue;
+        else if (version < 0 || version > 1)
+            Rf_error("File is not in ANALYZE-7.5 or NIfTI-1 format");
+        header = *((nifti_1_header *) ptr);
+        free(ptr);
+    }
+    else
+    {
+        const NiftiImage image(_image, false, true);
+        if (image.isNull())
+            return R_NilValue;
+        nifti_convert_nim2n1hdr(image, &header);
+    }
+
     nifti_analyze75 *analyze = (nifti_analyze75 *) &header;
     List result;