[sfnt] add compress function to optionally use zopfli instead of zlib

Lib/fontTools/ttLib/sfnt.py

@@ -133,6 +133,46 @@ class SFNTReader(object):
 		self.file.close()
 
 
+# default compression level for WOFF 1.0 tables and metadata
+ZLIB_COMPRESSION_LEVEL = 6
+
+# if set to True, use zopfli instead of zlib for compressing WOFF 1.0.
+# The Python bindings are available at https://github.com/anthrotype/py-zopfli
+USE_ZOPFLI = False
+
+# mapping between zlib's compression levels and zopfli's 'numiterations'.
+# Use lower values for files over several MB in size or it will be too slow
+ZOPFLI_LEVELS = {
+	# 0: 0,  # can't do 0 iterations...
+	1: 1,
+	2: 3,
+	3: 5,
+	4: 8,
+	5: 10,
+	6: 15,
+	7: 25,
+	8: 50,
+	9: 100,
+}
+
+
+def compress(data, level=ZLIB_COMPRESSION_LEVEL):
+	""" Compress 'data' to Zlib format. If 'USE_ZOPFLI' variable is True,
+	zopfli is used instead of the zlib module.
+	The compression 'level' must be between 0 and 9. 1 gives best speed,
+	9 gives best compression (0 gives no compression at all).
+	The default value is a compromise between speed and compression (6).
+	"""
+	if not (0 <= level <= 9):
+		raise ValueError('Bad compression level: %s' % level)
+	if not USE_ZOPFLI or level == 0:
+		from zlib import compress
+		return compress(data, level)
+	else:
+		from zopfli.zlib import compress
+		return compress(data, numiterations=ZOPFLI_LEVELS[level])
+
+
 class SFNTWriter(object):
 
 	def __new__(cls, *args, **kwargs):
@@ -246,8 +286,7 @@ class SFNTWriter(object):
 				self.metaOrigLength = len(data.metaData)
 				self.file.seek(0,2)
 				self.metaOffset = self.file.tell()
-				import zlib
-				compressedMetaData = zlib.compress(data.metaData)
+				compressedMetaData = compress(data.metaData)
 				self.metaLength = len(compressedMetaData)
 				self.file.write(compressedMetaData)
 			else:
@@ -439,7 +478,7 @@ class WOFFDirectoryEntry(DirectoryEntry):
 
 	format = woffDirectoryEntryFormat
 	formatSize = woffDirectoryEntrySize
-	zlibCompressionLevel = 6
+	zlibCompressionLevel = ZLIB_COMPRESSION_LEVEL
 
 	def decodeData(self, rawData):
 		import zlib
@@ -448,14 +487,13 @@ class WOFFDirectoryEntry(DirectoryEntry):
 		else:
 			assert self.length < self.origLength
 			data = zlib.decompress(rawData)
-			assert len (data) == self.origLength
+			assert len(data) == self.origLength
 		return data
 
 	def encodeData(self, data):
-		import zlib
 		self.origLength = len(data)
 		if not self.uncompressed:
-			compressedData = zlib.compress(data, self.zlibCompressionLevel)
+			compressedData = compress(data, self.zlibCompressionLevel)
 		if self.uncompressed or len(compressedData) >= self.origLength:
 			# Encode uncompressed
 			rawData = data