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[0]))
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).
extent=1
Expand the image to the dimension specified by the extent_size or the
size parameter. This is useful when maintain_ratio=1 leaves blanks on
the edges - set extent=1 and extent_anchor together can determine which
side the blank edges are placed
extent_size=NxM
Extent the resized image further to N pixels wide and M pixels high.
Default to size.
extent_anchor=(top|bottom|left|right|center|middle|topleft|topright
|bottomleft|bottomright)
Anchors the extent operation to one location of the image.
(ignored if extent or extent_size does not exist or is invalid).
Defaults to center
extent_background=Hex
The background color used for extending a source image.
The color should be specified by its Hex value, e.g. #FF0, #FFFF00, or
#FFFF00AA.
(ignored if extent or extent_size does not exist or is invalid).
Defaults to #00000000 (transparent)
extent_compose=(over|add|subtract)
The compose method used for extending a source image.
over - source image is composed over background color.
add - source image is added onto background color.
subtract - source image is subtracted from background color.
(ignored if extent or extent_size does not exist or is invalid).
Defaults to "over"
extent_shift=NxM
Shifts the image away from anchor position by N pixels padding on the left
and M pixels of padding on the top. Currently only positive integer values
are supported.
Note, if the shift + image size exceeds the extent_size, weird stuff will
likely happen.
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.
splice=1
Insert a space into the middle or edge of an image of dimensions
specified by the splice_size. This will result
in the overall size of the image increasing based on the addition.
splice_size=NxM
Dimensions of space to add into the middle or edge of an image.
splice_anchor=(top|bottom|left|right|center|middle|topleft|topright
|bottomleft|bottomright)
Anchors the splice operation to one location of the image.
(ignored if splice or splice_size does not exist or is invalid).
Defaults to center
splice_background=Hex
The background color used for splicing a source image.
The color should be specified by its Hex value, e.g. #FF0, #FFFF00, or
#FFFF00AA.
(ignored if splice or splice_size does not exist or is invalid).
Defaults to #00000000 (transparent)
splice_compose=(over|add|subtract)
The compose method used for splicing a source image.
over - source image is composed over background color.
add - source image is added onto background color.
subtract - source image is subtracted from background color.
(ignored if splice or splice_size does not exist or is invalid).
Defaults to "over"
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.
overlay_image=image1.png,image2.png,...
Applies each image as an overlay on the source image. The overlay image will be resized
to match the size of the source image. Overlays are applied before cropping. The images
specified must be present in a local directory, specified by self.local_image_dir.
Relative paths are not allowed, and a 500 will be thrown if one is encountered (preventing
clients from accessing files in other directories).
text_0=Some%20Text
text_0 through text_4 are used with their corresponding style params to overlay text onto a
given image. Text is applied before cropping. Text can be of any length, through whether
the text runs off the image or wraps is defined in the style.
style_0=some_style
style_0 through style_4 are used with their corresponding text params to overlay text onto a
given image. Text is applied before cropping. Styles must be defined and are obtained
through get_style, without modification no styles exist and no text will be applied.
See example.py for more.
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