fixes #546

Author: jph00

fastcore/_modidx.py

@@ -331,6 +331,7 @@
                                      'fastcore.foundation.working_directory': ( 'foundation.html#working_directory',
                                                                                 'fastcore/foundation.py'),
                                      'fastcore.foundation.zip_cycle': ('foundation.html#zip_cycle', 'fastcore/foundation.py')},
+            'fastcore.imghdr': {},
             'fastcore.imports': {},
             'fastcore.meta': { 'fastcore.meta.AutoInit': ('meta.html#autoinit', 'fastcore/meta.py'),
                                'fastcore.meta.AutoInit.__pre_init__': ('meta.html#autoinit.__pre_init__', 'fastcore/meta.py'),

fastcore/imghdr.py

@@ -0,0 +1,169 @@
+"""Recognize image file formats based on their first few bytes."""
+
+from os import PathLike
+import warnings
+
+__all__ = ["what"]
+
+#-------------------------#
+# Recognize image headers #
+#-------------------------#
+
+def what(file, h=None):
+    f = None
+    try:
+        if h is None:
+            if isinstance(file, (str, PathLike)):
+                f = open(file, 'rb')
+                h = f.read(32)
+            else:
+                location = file.tell()
+                h = file.read(32)
+                file.seek(location)
+        for tf in tests:
+            res = tf(h, f)
+            if res:
+                return res
+    finally:
+        if f: f.close()
+    return None
+
+
+#---------------------------------#
+# Subroutines per image file type #
+#---------------------------------#
+
+tests = []
+
+def test_jpeg(h, f):
+    """JPEG data with JFIF or Exif markers; and raw JPEG"""
+    if h[6:10] in (b'JFIF', b'Exif') or h[:4] in (b'\xff\xd8\xff\xdb',b'\xff\xd8\xff\xe2',b'\xff\xd8\xff\xe1'):
+        return 'jpeg'
+
+tests.append(test_jpeg)
+
+def test_png(h, f):
+    if h.startswith(b'\211PNG\r\n\032\n'):
+        return 'png'
+
+tests.append(test_png)
+
+def test_gif(h, f):
+    """GIF ('87 and '89 variants)"""
+    if h[:6] in (b'GIF87a', b'GIF89a'):
+        return 'gif'
+
+tests.append(test_gif)
+
+def test_tiff(h, f):
+    """TIFF (can be in Motorola or Intel byte order)"""
+    if h[:2] in (b'MM', b'II'):
+        return 'tiff'
+
+tests.append(test_tiff)
+
+def test_rgb(h, f):
+    """SGI image library"""
+    if h.startswith(b'\001\332'):
+        return 'rgb'
+
+tests.append(test_rgb)
+
+def test_pbm(h, f):
+    """PBM (portable bitmap)"""
+    if len(h) >= 3 and \
+        h[0] == ord(b'P') and h[1] in b'14' and h[2] in b' \t\n\r':
+        return 'pbm'
+
+tests.append(test_pbm)
+
+def test_pgm(h, f):
+    """PGM (portable graymap)"""
+    if len(h) >= 3 and \
+        h[0] == ord(b'P') and h[1] in b'25' and h[2] in b' \t\n\r':
+        return 'pgm'
+
+tests.append(test_pgm)
+
+def test_ppm(h, f):
+    """PPM (portable pixmap)"""
+    if len(h) >= 3 and \
+        h[0] == ord(b'P') and h[1] in b'36' and h[2] in b' \t\n\r':
+        return 'ppm'
+
+tests.append(test_ppm)
+
+def test_rast(h, f):
+    """Sun raster file"""
+    if h.startswith(b'\x59\xA6\x6A\x95'):
+        return 'rast'
+
+tests.append(test_rast)
+
+def test_xbm(h, f):
+    """X bitmap (X10 or X11)"""
+    if h.startswith(b'#define '):
+        return 'xbm'
+
+tests.append(test_xbm)
+
+def test_bmp(h, f):
+    if h.startswith(b'BM'):
+        return 'bmp'
+
+tests.append(test_bmp)
+
+def test_webp(h, f):
+    if h.startswith(b'RIFF') and h[8:12] == b'WEBP':
+        return 'webp'
+
+tests.append(test_webp)
+
+def test_exr(h, f):
+    if h.startswith(b'\x76\x2f\x31\x01'):
+        return 'exr'
+
+tests.append(test_exr)
+
+#--------------------#
+# Small test program #
+#--------------------#
+
+def test():
+    import sys
+    recursive = 0
+    if sys.argv[1:] and sys.argv[1] == '-r':
+        del sys.argv[1:2]
+        recursive = 1
+    try:
+        if sys.argv[1:]:
+            testall(sys.argv[1:], recursive, 1)
+        else:
+            testall(['.'], recursive, 1)
+    except KeyboardInterrupt:
+        sys.stderr.write('\n[Interrupted]\n')
+        sys.exit(1)
+
+def testall(list, recursive, toplevel):
+    import sys
+    import os
+    for filename in list:
+        if os.path.isdir(filename):
+            print(filename + '/:', end=' ')
+            if recursive or toplevel:
+                print('recursing down:')
+                import glob
+                names = glob.glob(os.path.join(glob.escape(filename), '*'))
+                testall(names, recursive, 0)
+            else:
+                print('*** directory (use -r) ***')
+        else:
+            print(filename + ':', end=' ')
+            sys.stdout.flush()
+            try:
+                print(what(filename))
+            except OSError:
+                print('*** not found ***')
+
+if __name__ == '__main__':
+    test()

fastcore/xtras.py

@@ -91,7 +91,8 @@ def mkdir(path, exist_ok=False, parents=False, overwrite=False, **kwargs):
 # %% ../nbs/03_xtras.ipynb 28
 def image_size(fn):
     "Tuple of (w,h) for png, gif, or jpg; `None` otherwise"
-    import imghdr,struct
+    from fastcore import imghdr
+    import struct
     def _jpg_size(f):
         size,ftype = 2,0
         while not 0xc0 <= ftype <= 0xcf:

nbs/03_xtras.ipynb

@@ -208,7 +208,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "import imghdr"
+    "from fastcore import imghdr"
    ]
   },
   {
@@ -375,7 +375,8 @@
     "#|export\n",
     "def image_size(fn):\n",
     "    \"Tuple of (w,h) for png, gif, or jpg; `None` otherwise\"\n",
-    "    import imghdr,struct\n",
+    "    from fastcore import imghdr\n",
+    "    import struct\n",
     "    def _jpg_size(f):\n",
     "        size,ftype = 2,0\n",
     "        while not 0xc0 <= ftype <= 0xcf:\n",