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ENH: Add metadata reading functions

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Required small refactoring of file IO to provide a saner interface.
This commit is contained in:
Zach Pincus
2012-02-01 22:48:01 -05:00
parent 3a1641f799
commit b5dce45446
1 changed files with 106 additions and 37 deletions
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skimage/io/_plugins/freeimage_plugin.py
+106 -37
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@@ -110,12 +110,14 @@ API = {
# systems. Thanks, ctypes! So after these calls one must immediately
# re-wrap the int as a c_void_p if it is to be passed back into FreeImage.
'FreeImage_AllocateT': (ctypes.c_void_p, None),
'FreeImage_FindFirstMetadata': (ctypes.c_void_p, None),
'FreeImage_GetBits': (ctypes.c_void_p, None),
'FreeImage_GetPalette': (ctypes.c_void_p, None),
'FreeImage_GetTagKey': (ctypes.c_char_p, None),
'FreeImage_GetTagValue': (ctypes.c_void_p, None),
'FreeImage_Load': (ctypes.c_void_p, None),
'FreeImage_LockPage': (ctypes.c_void_p, None),
'FreeImage_OpenMultiBitmap': (ctypes.c_void_p, None),
'FreeImage_OpenMultiBitmap': (ctypes.c_void_p, None)
}
# Albert's ctypes pattern
@@ -277,7 +279,6 @@ class IO_FLAGS(object):
XBM_DEFAULT = 0
class METADATA_MODELS(object):
FIMD_NODATA = -1
FIMD_COMMENTS = 0
FIMD_EXIF_MAIN = 1
FIMD_EXIF_EXIF = 2
@@ -288,26 +289,75 @@ class METADATA_MODELS(object):
FIMD_XMP = 7
FIMD_GEOTIFF = 8
FIMD_ANIMATION = 9
FIMD_CUSTOM = 10
class METADATA_DATATYPE(object):
FIDT_BYTE = 1 # 8-bit unsigned integer
FIDT_ASCII = 2 # 8-bit bytes w/ last byte null
FIDT_SHORT = 3 # 16-bit unsigned integer
FIDT_LONG = 4 # 32-bit unsigned integer
FIDT_RATIONAL = 5 # 64-bit unsigned fraction
FIDT_SBYTE = 6 # 8-bit signed integer
FIDT_UNDEFINED = 7 # 8-bit untyped data
FIDT_SSHORT = 8 # 16-bit signed integer
FIDT_SLONG = 9 # 32-bit signed integer
FIDT_SRATIONAL = 10 # 64-bit signed fraction
FIDT_FLOAT = 11 # 32-bit IEEE floating point
FIDT_DOUBLE = 12 # 64-bit IEEE floating point
FIDT_IFD = 13 # 32-bit unsigned integer (offset)
FIDT_PALETTE = 14 # 32-bit RGBQUAD
dtypes = {
FIDT_BYTE: numpy.uint8,
FIDT_SHORT: numpy.uint16,
FIDT_LONG: numpy.uint32,
FIDT_RATIONAL: [('numerator', numpy.uint32),
('denominator', numpy.uint32)],
FIDT_SBYTE: numpy.int8,
FIDT_UNDEFINED: numpy.uint8,
FIDT_SSHORT: numpy.int16,
FIDT_SLONG: numpy.int32,
FIDT_SRATIONAL: [('numerator', numpy.int32),
('denominator', numpy.int32)],
FIDT_FLOAT: numpy.float32,
FIDT_DOUBLE: numpy.float64,
FIDT_IFD: numpy.uint32,
FIDT_PALETTE: [('R', numpy.uint8), ('G', numpy.uint8),
('B', numpy.uint8), ('A', numpy.uint8)]
}
def _process_bitmap(filename, flags, process_func):
filename = asbytes(filename)
ftype = _FI.FreeImage_GetFileType(filename, 0)
if ftype == -1:
raise ValueError('Cannot determine type of file %s' % filename)
bitmap = _FI.FreeImage_Load(ftype, filename, flags)
bitmap = ctypes.c_void_p(bitmap)
if not bitmap:
raise ValueError('Could not load file %s' % filename)
try:
return process_func(bitmap)
finally:
_FI.FreeImage_Unload(bitmap)
def read(filename, flags=0):
"""Read an image to a numpy array of shape (width, height) for
greyscale images, or shape (width, height, nchannels) for RGB or
RGBA images.
"""
bitmap = _read_bitmap(filename, flags)
try:
return _array_from_bitmap(bitmap)
finally:
_FI.FreeImage_Unload(bitmap)
def read_multipage(filename, flags=0):
"""Read a multipage image to a list of numpy arrays, where each
array is of shape (width, height) for greyscale images, or shape
(nchannels, width, height) for RGB or RGBA images.
return _process_bitmap(filename, flags, _array_from_bitmap)
def read_metadata(filename, flags=0):
"""Return a dict containing all image metadata.
Returned dict maps (metadata_model, tag_name) keys to tag values, where
metadata_model is a string name based on the FreeImage "metadata models"
defined in the class METADATA_MODELS.
"""
return _process_bitmap(filename, flags, _read_metadata)
def _process_multipage(filename, flags, process_func):
filename = asbytes(filename)
ftype = _FI.FreeImage_GetFileType(filename, 0)
if ftype == -1:
@@ -323,7 +373,7 @@ def read_multipage(filename, flags=0):
raise ValueError('Could not open %s as multi-page image.' % filename)
try:
pages = _FI.FreeImage_GetPageCount(multibitmap)
arrays = []
out = []
for i in range(pages):
bitmap = _FI.FreeImage_LockPage(multibitmap, i)
bitmap = ctypes.c_void_p(bitmap)
@@ -331,24 +381,25 @@ def read_multipage(filename, flags=0):
raise ValueError('Could not open %s as a multi-page image.'
% filename)
try:
arrays.append(_array_from_bitmap(bitmap))
out.append(process_func(bitmap))
finally:
_FI.FreeImage_UnlockPage(multibitmap, bitmap, False)
return arrays
return out
finally:
_FI.FreeImage_CloseMultiBitmap(multibitmap, 0)
def _read_bitmap(filename, flags):
"""Load a file to a FreeImage bitmap pointer"""
filename = asbytes(filename)
ftype = _FI.FreeImage_GetFileType(filename, 0)
if ftype == -1:
raise ValueError('Cannot determine type of file %s' % filename)
bitmap = _FI.FreeImage_Load(ftype, filename, flags)
bitmap = ctypes.c_void_p(bitmap)
if not bitmap:
raise ValueError('Could not load file %s' % filename)
return bitmap
def read_multipage(filename, flags=0):
"""Read a multipage image to a list of numpy arrays, where each
array is of shape (width, height) for greyscale images, or shape
(nchannels, width, height) for RGB or RGBA images.
"""
return _process_multipage(filename, flags, _array_from_bitmap)
def read_multipage_metadata(filename, flags=0):
"""Read a multipage image to a list of metadata dicts, one dict for each
page. The dict format is as in read_metadata().
"""
return _process_multipage(filename, flags, _read_metadata)
def _wrap_bitmap_bits_in_array(bitmap, shape, dtype):
"""Return an ndarray view on the data in a FreeImage bitmap. Only
@@ -399,17 +450,35 @@ def _array_from_bitmap(bitmap):
# after bitmap is freed.
return n(array).copy()
def _string_tag(bitmap, key, model=METADATA_MODELS.FIMD_EXIF_MAIN):
"""Retrieve the value of a metadata tag with the given string key as a
string.
def _read_metadata(bitmap):
metadata = {}
models = [(name[5:], number) for name, number in
METADATA_MODELS.__dict__.items() if name.startswith('FIMD_')]
"""
tag = ctypes.c_void_p()
if not _FI.FreeImage_GetMetadata(model, bitmap, str(key),
ctypes.byref(tag)):
return
char_ptr = ctypes.c_char * _FI.FreeImage_GetTagLength(tag)
return char_ptr.from_address(_FI.FreeImage_GetTagValue(tag)).raw()
for model_name, number in models:
mdhandle = _FI.FreeImage_FindFirstMetadata(number, bitmap,
ctypes.byref(tag))
mdhandle = ctypes.c_void_p(mdhandle)
if mdhandle:
more = True
while more:
tag_name = str(_FI.FreeImage_GetTagKey(tag))
tag_type = _FI.FreeImage_GetTagType(tag)
byte_size = _FI.FreeImage_GetTagLength(tag)
char_ptr = ctypes.c_char * byte_size
tag_str = char_ptr.from_address(_FI.FreeImage_GetTagValue(tag))
if tag_type == METADATA_DATATYPE.FIDT_ASCII:
tag_val = str(tag_str.value)
else:
tag_val = numpy.fromstring(tag_str,
dtype=METADATA_DATATYPE.dtypes[tag_type])
if len(tag_val) == 1:
tag_val = tag_val[0]
metadata[(model_name, tag_name)] = tag_val
more = _FI.FreeImage_FindNextMetadata(mdhandle, ctypes.byref(tag))
_FI.FreeImage_FindCloseMetadata(mdhandle)
return metadata
def write(array, filename, flags=0):
"""Write a (width, height) or (width, height, nchannels) array to