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A caching, resizing image proxy written in Go
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Will Norris b165ea8f12 update documentation for options
2013-12-06 17:02:11 -08:00
cache add basic caching support 2013-12-04 02:55:56 -08:00
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proxy allow percentage sizes 2013-12-06 15:03:17 -08:00
transform allow percentage sizes 2013-12-06 15:03:17 -08:00
.gitignore parse http requests to image requests 2013-11-27 11:13:54 -08:00
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readme.md update documentation for options 2013-12-06 17:02:11 -08:00

readme.md

go-imageproxy

go-imageproxy is a caching image proxy server written in golang. It supports dynamic image resizing and URL whitelisting.

This project was inspired by, and is designed to be an alternative to, WordPress's photon service. Photon is a great free service, but is limited to sites hosted on WordPress.com, or that use the Jetpack plugin. If you don't want to use Jetpack, then you're asked to use a different service. If you're looking for an alternative hosted service, I'd recommend resize.ly, embed.ly, or cloudinary. I decided to try building my own for fun.

URL Structure

go-imageproxy URLs are of the form http://localhost/{options}/{remote_url}.

Options

Options are specified as a comma delimited list of parameters, the first of which always specifies image size. The format is a superset of resize.ly's options.

Size

The size option takes the general form {width}x{height}, where width and height are numbers. Integer values greater than 1 are interpreted as exact pixel values. Floats between 0 and 1 are interpreted as percentages of the original image size. If either value is omitted or set to 0, it will be automatically set to preserve the aspect ratio based on the other dimension. If a single number is provided (with no "x" separator), it will be used for both height and width.

Crop Mode

Depending on the options specified, an image may be cropped to fit the requested size. In all cases, the original aspect ratio of the image will be preserved; go-imageproxy will never stretch the original image.

When no explicit crop mode is specified, the following rules are followed:

  • If both width and height values are specified, the image will be scaled to fill the space, cropping if necessary to fit the exact dimension.

  • If only one of the width or height values is specified, the image will be resized to fit the specified dimension, scaling the other dimension as needed to maintain the aspect ratio.

If the fit option is specified together with a width and height value, the image will be resized to fit within a containing box of the specified size. As always, the original aspect ratio will be preserved. Specifying the fit option with only one of either width or height does the same thing as if fit had not been specified.

Remote URL

The URL of the original image to load is specified as the remainder of the path, without any encoding. For example, http://localhost/200/https://willnorris.com/logo.jpg.

In order to optimize caching, it is recommended that URLs not contain query strings.

Examples

The following live examples demonstrate setting different options on this source image, which measures 1024x678 pixels.

Options Meaning Image
200x 200px wide, proportional height 200x
0.15x 15% original width, proportional height 0.15x
x100 100px tall, proportional width x100
100x150 100 by 150 pixels, cropping as needed 100x150
100 100px square, cropping as needed 100
150,fit fit to be no more than 150 by 150 pixels 150,fit

License

This application is distributed under the BSD-style license found in the LICENSE file.