Set of Tornado request handlers that allows on-the-fly conversion of images according to a request's query string options. Ectyper, by default, provides a way to resize, reflect and reformat images.
from ectyper.handlers import ImageHandler import os from tornado import web, ioloop class StreamLocal(ImageHandler): """ Trivial local file handler. It loads files in images directory, converts it and streams it to the client. Example calls: Resize: http://host:8888/images/hulu.jpg?size=200x96 Reformat: http://host:8888/images/hulu.jpg?format=png Reflect: http://host:8888/images/hulu.jpg?size=200x96&format=png&reflection_height=60 """ def calculate_options(self): super(StreamLocal, self).calculate_options() # By default Ectyper uses "convert" as found in the PATH of the running # python process, use this to override. if self.magick: self.magick.convert_path = "/path/to/imagemagick/convert" def handler(self, *args): self.convert_image(os.path.join("/path/to/images", args)) app = web.Application([ ('/images/(.*)', StreamLocal), ]) if __name__ == "__main__": app.listen(8888) ioloop.IOLoop.instance().start()
Ectyper provides a primary ImageHandler class (extending Tornado's RequestHandler class). This class parses each request's query string and converts it into a command-line call into ImageMagick's convert. This class is wrapped by ectyper.magick.ImageMagick which can be overridden to provide other options.
A request into an ImageHandler will automatically generate an ImageMagick object based on standard options (see help(ectyper.handlers.ImageHandler) for more). Once your handler calls convert_image() with a local file path or a remote URL, ImageHandler kicks off an ImageMagick convert process with the calculated options and streams the result to the browser. You can optionally extend CachingImageHandler or FileCachingImageHandler to stream the output elsewhere for caching purposes.
Full list of options supported by default:
size=NxM Resize the source image to N pixels wide and M pixels high. crop=1 Crops the image, maintaining aspect ratio, when resizing (ignored if size is not provided or maintain_ratio is not 1). Defaults to 0. crop_anchor=(top|bottom|left|right|center|middle|topleft|topright |bottomleft|bottomright) Anchors the crop to one location of the image. (ignored if crop and maintain_ratio are not both 1). Defaults to center maintain_ratio=1 Maintain aspect ratio when resizing (ignored if size is not provided). post_crop_size=NxM Applies a secondary "post-crop" to the image, after the standard image resize is performed. This supports the case where an image needs to be sized to fit a particular dimension using a crop, then the image needs to be chopped up into different regions. Defaults to None, meaning that no post-crop is applied. post_crop_anchor=(top|bottom|left|right|center|middle|topleft|topright |bottomleft|bottomright) Anchors the post-crop to one location of the image. (ignored if post_crop_size does not exist or is invalid). Defaults to center reflection_height=N Flip the image upside down and apply a gradient to mimic a reflected image. reflection_alpha_top and reflection_alpha_bottom can be used to set the gradient parameters. reflection_alpha_top=N The top value to use when generating the gradient for reflection_height, ignored if that parameter is not set. Should be between 0 and 1. Defaults to 1. reflection_alpha_bottom=N The bottom value to use when generating the gradient for reflection_height, ignored if that parameter is not set. Should be between 0 and 1. Defaults to 0. format=(jpeg|png|png16) Format to convert the image into. Defaults to jpeg. png16 is 24-bit png pre-dithered for 16-bit (RGB555) screens. &normalize=1 Histogram-based contrast increase. It passes the -normalize operator to ImageMagick. The top two percent of the dark pixels will become black and the top one percent of the light pixels will become white. The contrast of the rest of the pixels are maximized. All the channels are normalized together to avoid color shift, so pure black or white may not exist in the final image. Defaults to 0, which won't chain any operator to the ImageMagick command. &equalize=1 Histogram-based colour redistribution. It passes the -equalize operator to ImageMagick, following the -normalize operator. It redistributes the colour of the image according to uniform distribution. Each channel are changed independently, and color shift may happen. Default to 0, which won't chain any operator to the ImageMagick command. &contrast_stretch=axb Histogram-based contrast adjustment. It passes the -contrast-stretch a%xb% operator to ImageMagick, following the -equalize operator. The top a percent of the dark pixels will become black and the top b percent of the light pixels will become white. The contrast of the rest of the pixels are maximized. All the channels are normalized together to avoid color shift, so pure black or white may not exist in the final image. Defaults to None, which won't chain any operator to the ImageMagick command. &brightness_contrast=cxd Amplify brightness and contrast by percentages. It passes the -brightness-contrast c%xd% operator to ImageMagick, following the -contrast-stretch operator. Defaults to None, which won't chain any operator to the ImageMagick command.
See example.py for more.
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