"""Recognize image file formats based on their first few bytes.""" from os import PathLike __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 in JFIF or Exif format""" if h[6:10] in (b'JFIF', b'Exif'): 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()