Merge pull request #412 from ufo-kit/enable-writer-offset

storage: add start index to image writing

concert/storage.py

@@ -75,13 +75,15 @@ def create_directory(directory, rights=0o0750):
 
 
 @coroutine
-def write_images(writer=TiffWriter, prefix="image_{:>05}.tif", bytes_per_file=0):
+def write_images(writer=TiffWriter, prefix="image_{:>05}.tif", start_index=0, bytes_per_file=0):
     """
-    write_images(writer=TiffWriter, prefix="image_{:>05}.tif", bytes_per_file=0)
+    write_images(writer=TiffWriter, prefix="image_{:>05}.tif", start_index=0, bytes_per_file=0)
 
     Write images on disk with specified *writer* and file name *prefix*. Write to one file until the
     *bytes_per_file* bytes has been written. If it is 0, then one file per image is created.
-    *writer* is a subclass of :class:`.writers.ImageWriter`.
+    *writer* is a subclass of :class:`.writers.ImageWriter`. *start_index* specifies the number in
+    the first file name, e.g. for the default *prefix* and *start_index* 100, the first file name
+    will be image_00100.tif.
     """
     im_writer = None
     file_index = 0
@@ -97,7 +99,7 @@ def write_images(writer=TiffWriter, prefix="image_{:>05}.tif", bytes_per_file=0)
             if not im_writer or written + image.nbytes > bytes_per_file:
                 if im_writer:
                     im_writer.close()
-                im_writer = writer(prefix.format(file_index), bytes_per_file)
+                im_writer = writer(prefix.format(start_index + file_index), bytes_per_file)
                 file_index += 1
                 written = 0
             im_writer.write(image)
@@ -221,11 +223,12 @@ class DirectoryWalker(Walker):
     specific filename template.
     """
 
-    def __init__(self, writer=TiffWriter, dsetname='frame_{:>06}.tif', bytes_per_file=0,
-                 root=None, log=None, log_name='experiment.log'):
+    def __init__(self, writer=TiffWriter, dsetname='frame_{:>06}.tif', start_index=0,
+                 bytes_per_file=0, root=None, log=None, log_name='experiment.log'):
         """
-        Use *writer* to write data to files with filenames with a template
-        from *dsetname*.
+        Use *writer* to write data to files with filenames with a template from *dsetname*.
+        *start_index* specifies the number in the first file name, e.g. for the default *dsetname*
+        and *start_index* 100, the first file name will be frame_000100.tif.
         """
         if not root:
             root = os.getcwd()
@@ -242,6 +245,7 @@ def __init__(self, writer=TiffWriter, dsetname='frame_{:>06}.tif', bytes_per_fil
                                               log=log, log_handler=log_handler)
         self._writer = writer
         self._bytes_per_file = bytes_per_file
+        self._start_index = start_index
 
     def _descend(self, name):
         self._current = os.path.join(self._current, name)
@@ -267,6 +271,7 @@ def _write_coroutine(self, dsetname=None):
 
         prefix = os.path.join(self._current, dsetname)
         return write_images(writer=self._writer, prefix=prefix,
+                            start_index=self._start_index,
                             bytes_per_file=self._bytes_per_file)
 
     def _dset_exists(self, dsetname):