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Source code for kivy.loader

Asynchronous data loader

This is the Asynchronous Loader. You can use it to load an image
and use it, even if data are not yet available. You must specify a default
loading image when using the loader::

    from kivy.loader import Loader
    image = Loader.image('mysprite.png')

You can also load an image from a url::

    image = Loader.image('http://mysite.com/test.png')

If you want to change the default loading image, you can do::

    Loader.loading_image = Image('another_loading.png')

Tweaking the asynchronous loader

.. versionadded:: 1.6.0

You can tweak the loader to provide a better user experience or more
performance, depending of the images you are going to load. Take a look at the

- :attr:`Loader.num_workers` - define the number of threads to start for
  loading images.
- :attr:`Loader.max_upload_per_frame` - define the maximum image uploads in
  GPU to do per frame.


__all__ = ('Loader', 'LoaderBase', 'ProxyImage')

from kivy import kivy_data_dir
from kivy.logger import Logger
from kivy.clock import Clock
from kivy.cache import Cache
from kivy.core.image import ImageLoader, Image
from kivy.compat import PY2, string_types

from collections import deque
from time import sleep
from os.path import join
from os import write, close, unlink, environ
import threading
import mimetypes

# Register a cache for loader
Cache.register('kv.loader', limit=500, timeout=60)

[docs]class ProxyImage(Image): '''Image returned by the Loader.image() function. :Properties: `loaded`: bool, defaults to False This value may be True if the image is already cached. :Events: `on_load` Fired when the image is loaded or changed. `on_error` Fired when the image cannot be loaded. `error`: Exception data that ocurred ''' __events__ = ('on_load', 'on_error') def __init__(self, arg, **kwargs): loaded = kwargs.pop('loaded', False) super(ProxyImage, self).__init__(arg, **kwargs) self.loaded = loaded def on_load(self): pass def on_error(self, error): pass
[docs]class LoaderBase(object): '''Common base for the Loader and specific implementations. By default, the Loader will be the best available loader implementation. The _update() function is called every 1 / 25.s or each frame if we have less than 25 FPS. ''' _trigger_update = None def __init__(self): self._loading_image = None self._error_image = None self._num_workers = 2 self._max_upload_per_frame = 2 self._paused = False self._resume_cond = threading.Condition() self._q_load = deque() self._q_done = deque() self._client = [] self._running = False self._start_wanted = False self._trigger_update = Clock.create_trigger(self._update) def __del__(self): if self._trigger_update is not None: self._trigger_update.cancel() def _set_num_workers(self, num): if num < 2: raise Exception('Must have at least 2 workers') self._num_workers = num def _get_num_workers(self): return self._num_workers num_workers = property(_get_num_workers, _set_num_workers) '''Number of workers to use while loading (used only if the loader implementation supports it). This setting impacts the loader only on initialization. Once the loader is started, the setting has no impact:: from kivy.loader import Loader Loader.num_workers = 4 The default value is 2 for giving a smooth user experience. You could increase the number of workers, then all the images will be loaded faster, but the user will not been able to use the application while loading. Prior to 1.6.0, the default number was 20, and loading many full-hd images was completly blocking the application. .. versionadded:: 1.6.0 ''' def _set_max_upload_per_frame(self, num): if num is not None and num < 1: raise Exception('Must have at least 1 image processing per image') self._max_upload_per_frame = num def _get_max_upload_per_frame(self): return self._max_upload_per_frame max_upload_per_frame = property(_get_max_upload_per_frame, _set_max_upload_per_frame) '''The number of images to upload per frame. By default, we'll upload only 2 images to the GPU per frame. If you are uploading many small images, you can easily increase this parameter to 10 or more. If you are loading multiple full HD images, the upload time may have consequences and block the application. If you want a smooth experience, use the default. As a matter of fact, a Full-HD RGB image will take ~6MB in memory, so it may take time. If you have activated mipmap=True too, then the GPU must calculate the mipmap of these big images too, in real time. Then it may be best to reduce the :attr:`max_upload_per_frame` to 1 or 2. If you want to get rid of that (or reduce it a lot), take a look at the DDS format. .. versionadded:: 1.6.0 ''' def _get_loading_image(self): if not self._loading_image: loading_png_fn = join(kivy_data_dir, 'images', 'image-loading.gif') self._loading_image = ImageLoader.load(filename=loading_png_fn) return self._loading_image def _set_loading_image(self, image): if isinstance(image, string_types): self._loading_image = ImageLoader.load(filename=image) else: self._loading_image = image loading_image = property(_get_loading_image, _set_loading_image) '''Image used for loading. You can change it by doing:: Loader.loading_image = 'loading.png' .. versionchanged:: 1.6.0 Not readonly anymore. ''' def _get_error_image(self): if not self._error_image: error_png_fn = join( 'atlas://data/images/defaulttheme/image-missing') self._error_image = ImageLoader.load(filename=error_png_fn) return self._error_image def _set_error_image(self, image): if isinstance(image, string_types): self._error_image = ImageLoader.load(filename=image) else: self._error_image = image error_image = property(_get_error_image, _set_error_image) '''Image used for error. You can change it by doing:: Loader.error_image = 'error.png' .. versionchanged:: 1.6.0 Not readonly anymore. '''
[docs] def start(self): '''Start the loader thread/process.''' self._running = True
[docs] def run(self, *largs): '''Main loop for the loader.''' pass
[docs] def stop(self): '''Stop the loader thread/process.''' self._running = False
[docs] def pause(self): '''Pause the loader, can be useful during interactions. .. versionadded:: 1.6.0 ''' self._paused = True
[docs] def resume(self): '''Resume the loader, after a :meth:`pause`. .. versionadded:: 1.6.0 ''' self._paused = False self._resume_cond.acquire() self._resume_cond.notify_all() self._resume_cond.release()
def _wait_for_resume(self): while self._running and self._paused: self._resume_cond.acquire() self._resume_cond.wait(0.25) self._resume_cond.release() def _load(self, kwargs): '''(internal) Loading function, called by the thread. Will call _load_local() if the file is local, or _load_urllib() if the file is on Internet. ''' while len(self._q_done) >= ( self.max_upload_per_frame * self._num_workers): sleep(0.1) self._wait_for_resume() filename = kwargs['filename'] load_callback = kwargs['load_callback'] post_callback = kwargs['post_callback'] try: proto = filename.split(':', 1)[0] except: # if blank filename then return return if load_callback is not None: data = load_callback(filename) elif proto in ('http', 'https', 'ftp', 'smb'): data = self._load_urllib(filename, kwargs['kwargs']) else: data = self._load_local(filename, kwargs['kwargs']) if post_callback: data = post_callback(data) self._q_done.appendleft((filename, data)) self._trigger_update() def _load_local(self, filename, kwargs): '''(internal) Loading a local file''' # With recent changes to CoreImage, we must keep data otherwise, # we might be unable to recreate the texture afterwise. return ImageLoader.load(filename, keep_data=True, **kwargs) def _load_urllib(self, filename, kwargs): '''(internal) Loading a network file. First download it, save it to a temporary file, and pass it to _load_local().''' if PY2: import urllib2 as urllib_request def gettype(info): return info.gettype() else: import urllib.request as urllib_request def gettype(info): return info.get_content_type() proto = filename.split(':', 1)[0] if proto == 'smb': try: # note: it's important to load SMBHandler every time # otherwise the data is occasionally not loaded from smb.SMBHandler import SMBHandler except ImportError: Logger.warning( 'Loader: can not load PySMB: make sure it is installed') return import tempfile data = fd = _out_osfd = None try: _out_filename = '' if proto == 'smb': # read from samba shares fd = urllib_request.build_opener(SMBHandler).open(filename) else: # read from internet fd = urllib_request.urlopen(filename) if '#.' in filename: # allow extension override from URL fragment suffix = '.' + filename.split('#.')[-1] else: ctype = gettype(fd.info()) suffix = mimetypes.guess_extension(ctype) if not suffix: # strip query string and split on path parts = filename.split('?')[0].split('/')[1:] while len(parts) > 1 and not parts[0]: # strip out blanks from '//' parts = parts[1:] if len(parts) > 1 and '.' in parts[-1]: # we don't want '.com', '.net', etc. as the extension suffix = '.' + parts[-1].split('.')[-1] _out_osfd, _out_filename = tempfile.mkstemp( prefix='kivyloader', suffix=suffix) idata = fd.read() fd.close() fd = None # write to local filename write(_out_osfd, idata) close(_out_osfd) _out_osfd = None # load data data = self._load_local(_out_filename, kwargs) # FIXME create a clean API for that for imdata in data._data: imdata.source = filename except Exception as ex: Logger.exception('Loader: Failed to load image <%s>' % filename) # close file when remote file not found or download error try: if _out_osfd: close(_out_osfd) except OSError: pass # update client for c_filename, client in self._client[:]: if filename != c_filename: continue # got one client to update client.image = self.error_image client.dispatch('on_error', error=ex) self._client.remove((c_filename, client)) return self.error_image finally: if fd: fd.close() if _out_osfd: close(_out_osfd) if _out_filename != '': unlink(_out_filename) return data def _update(self, *largs): '''(internal) Check if a data is loaded, and pass to the client.''' # want to start it ? if self._start_wanted: if not self._running: self.start() self._start_wanted = False # in pause mode, don't unqueue anything. if self._paused: self._trigger_update() return for x in range(self.max_upload_per_frame): try: filename, data = self._q_done.pop() except IndexError: return # create the image image = data # ProxyImage(data) if not image.nocache: Cache.append('kv.loader', filename, image) # update client for c_filename, client in self._client[:]: if filename != c_filename: continue # got one client to update client.image = image client.loaded = True client.dispatch('on_load') self._client.remove((c_filename, client)) self._trigger_update()
[docs] def image(self, filename, load_callback=None, post_callback=None, **kwargs): '''Load a image using the Loader. A ProxyImage is returned with a loading image. You can use it as follows:: from kivy.app import App from kivy.uix.image import Image from kivy.loader import Loader class TestApp(App): def _image_loaded(self, proxyImage): if proxyImage.image.texture: self.image.texture = proxyImage.image.texture def build(self): proxyImage = Loader.image("myPic.jpg") proxyImage.bind(on_load=self._image_loaded) self.image = Image() return self.image TestApp().run() In order to cancel all background loading, call *Loader.stop()*. ''' data = Cache.get('kv.loader', filename) if data not in (None, False): # found image, if data is not here, need to reload. return ProxyImage(data, loading_image=self.loading_image, loaded=True, **kwargs) client = ProxyImage(self.loading_image, loading_image=self.loading_image, **kwargs) self._client.append((filename, client)) if data is None: # if data is None, this is really the first time self._q_load.appendleft({ 'filename': filename, 'load_callback': load_callback, 'post_callback': post_callback, 'kwargs': kwargs}) if not kwargs.get('nocache', False): Cache.append('kv.loader', filename, False) self._start_wanted = True self._trigger_update() else: # already queued for loading pass return client
# # Loader implementation # if 'KIVY_DOC' in environ: Loader = None else: # # Try to use pygame as our first choice for loader # from kivy.compat import queue from threading import Thread class _Worker(Thread): '''Thread executing tasks from a given tasks queue ''' def __init__(self, pool, tasks): Thread.__init__(self) self.tasks = tasks self.daemon = True self.pool = pool self.start() def run(self): while self.pool.running: func, args, kargs = self.tasks.get() try: func(*args, **kargs) except Exception as e: print(e) self.tasks.task_done() class _ThreadPool(object): '''Pool of threads consuming tasks from a queue ''' def __init__(self, num_threads): super(_ThreadPool, self).__init__() self.running = True self.tasks = queue.Queue() for _ in range(num_threads): _Worker(self, self.tasks) def add_task(self, func, *args, **kargs): '''Add a task to the queue ''' self.tasks.put((func, args, kargs)) def stop(self): self.running = False self.tasks.join() class LoaderThreadPool(LoaderBase): def __init__(self): super(LoaderThreadPool, self).__init__() self.pool = None def start(self): super(LoaderThreadPool, self).start() self.pool = _ThreadPool(self._num_workers) Clock.schedule_interval(self.run, 0) def stop(self): super(LoaderThreadPool, self).stop() Clock.unschedule(self.run) self.pool.stop() def run(self, *largs): while self._running: try: parameters = self._q_load.pop() except: return self.pool.add_task(self._load, parameters) Loader = LoaderThreadPool() Logger.info('Loader: using a thread pool of {} workers'.format( Loader.num_workers))