149 lines
5.6 KiB
Python
149 lines
5.6 KiB
Python
# -*- coding: utf-8 -*-
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# imageio is distributed under the terms of the (new) BSD License.
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""" Example plugin. You can use this as a template for your own plugin.
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"""
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import numpy as np
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from .. import formats
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from ..core import Format
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class DummyFormat(Format):
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""" The dummy format is an example format that does nothing.
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It will never indicate that it can read or write a file. When
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explicitly asked to read, it will simply read the bytes. When
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explicitly asked to write, it will raise an error.
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This documentation is shown when the user does ``help('thisformat')``.
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Parameters for reading
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----------------------
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Specify arguments in numpy doc style here.
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Parameters for saving
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---------------------
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Specify arguments in numpy doc style here.
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"""
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def _can_read(self, request):
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# This method is called when the format manager is searching
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# for a format to read a certain image. Return True if this format
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# can do it.
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#
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# The format manager is aware of the extensions and the modes
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# that each format can handle. It will first ask all formats
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# that *seem* to be able to read it whether they can. If none
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# can, it will ask the remaining formats if they can: the
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# extension might be missing, and this allows formats to provide
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# functionality for certain extensions, while giving preference
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# to other plugins.
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#
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# If a format says it can, it should live up to it. The format
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# would ideally check the request.firstbytes and look for a
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# header of some kind.
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#
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# The request object has:
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# request.filename: a representation of the source (only for reporting)
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# request.firstbytes: the first 256 bytes of the file.
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# request.mode[0]: read or write mode
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# request.mode[1]: what kind of data the user expects: one of 'iIvV?'
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if request.mode[1] in (self.modes + "?"):
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if request.extension in self.extensions:
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return True
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def _can_write(self, request):
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# This method is called when the format manager is searching
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# for a format to write a certain image. It will first ask all
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# formats that *seem* to be able to write it whether they can.
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# If none can, it will ask the remaining formats if they can.
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#
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# Return True if the format can do it.
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# In most cases, this code does suffice:
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if request.mode[1] in (self.modes + "?"):
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if request.extension in self.extensions:
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return True
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# -- reader
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class Reader(Format.Reader):
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def _open(self, some_option=False, length=1):
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# Specify kwargs here. Optionally, the user-specified kwargs
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# can also be accessed via the request.kwargs object.
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#
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# The request object provides two ways to get access to the
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# data. Use just one:
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# - Use request.get_file() for a file object (preferred)
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# - Use request.get_local_filename() for a file on the system
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self._fp = self.request.get_file()
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self._length = length # passed as an arg in this case for testing
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self._data = None
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def _close(self):
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# Close the reader.
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# Note that the request object will close self._fp
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pass
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def _get_length(self):
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# Return the number of images. Can be np.inf
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return self._length
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def _get_data(self, index):
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# Return the data and meta data for the given index
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if index >= self._length:
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raise IndexError("Image index %i > %i" % (index, self._length))
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# Read all bytes
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if self._data is None:
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self._data = self._fp.read()
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# Put in a numpy array
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im = np.frombuffer(self._data, "uint8")
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im.shape = len(im), 1
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# Return array and dummy meta data
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return im, {}
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def _get_meta_data(self, index):
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# Get the meta data for the given index. If index is None, it
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# should return the global meta data.
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return {} # This format does not support meta data
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# -- writer
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class Writer(Format.Writer):
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def _open(self, flags=0):
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# Specify kwargs here. Optionally, the user-specified kwargs
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# can also be accessed via the request.kwargs object.
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#
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# The request object provides two ways to write the data.
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# Use just one:
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# - Use request.get_file() for a file object (preferred)
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# - Use request.get_local_filename() for a file on the system
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self._fp = self.request.get_file()
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def _close(self):
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# Close the reader.
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# Note that the request object will close self._fp
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pass
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def _append_data(self, im, meta):
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# Process the given data and meta data.
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raise RuntimeError("The dummy format cannot write image data.")
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def set_meta_data(self, meta):
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# Process the given meta data (global for all images)
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# It is not mandatory to support this.
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raise RuntimeError("The dummy format cannot write meta data.")
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# Register. You register an *instance* of a Format class. Here specify:
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format = DummyFormat(
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"dummy", # short name
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"An example format that does nothing.", # one line descr.
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".foobar .nonexistentext", # list of extensions
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"iI", # modes, characters in iIvV
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)
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formats.add_format(format)
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