fanlin

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abstract

fanlin is image proxy server written in Go language.

Support

OS

• Linux (x86 and amd64)
• macOS

Go Versions

• Please see go.mod

Image Format

• JPEG
• PNG
• GIF
• WebP
• AVIF (encode only)

Requirements

Make sure libaom is installed for AVIF format encoding.

$ sudo apt install libaom-dev

Also, we need the following dependency for the conversion between CMYK and RGB color spaces with ICC profiles.

$ sudo apt install liblcms2-dev

Cross compile for amd64 Linux

$ GOOS=linux GOARCH=amd64 go build github.com/livesense-inc/fanlin/cmd/fanlin

testing

$ go test -cover ./...

configure

On Unix, Linux and macOS, fanlin programs read startup options from the following files, in the specified order(top files are read first, and precedence).

/etc/fanlin.json
/etc/fanlin.cnf
/etc/fanlin.conf
/usr/local/etc/fanlin.json
/usr/local/etc/fanlin.cnf
/usr/local/etc/fanlin.conf
./fanlin.json
./fanlin.cnf
./fanlin.conf
./conf.json
~/.fanlin.json
~/.fanlin.cnf

example

fanlin.json

{
    "port": 8080,
    "max_width": 1000,
    "max_height": 1000,
    "404_img_path": "/path/to/404/image",
    "access_log_path": "/path/to/access/log",
    "error_log_path": "/path/to/error/log",
    "use_server_timing": true,
    "providers": [
        {
            "/alias/0" : {
                "type" : "web",
                "src" : "http://aaa.com/bbb",
                "priority" : 10
            }
        },
        {
            "/alias/1" : {
                "type" : "web",
                "src" : "https://ccc.com",
                "priority" : 20
            }
        },
        {
            "/alias/3" : {
                "type" : "s3",
                "src" : "s3://bucket/path",
                "region" : "ap-northeast-1",
                "priority" : 30
            }
        }
    ]
}

Controling where logs are output to

You can output each log to a file by specifying the path in access_log_path/error_log_path/debug_log_path. If you want to output logs to standard output, specify /dev/stdout.

Using WebP and Limitations

You can get WebP image format with GET parameter webp=true requeest.

Examples:

• JPG image URL:
  • http://localhost:8080/abc.jpg?h=400&w=400&quality=80
• WebP encoded image URL:
  • http://localhost:8080/abc.jpg?h=400&w=400&quality=80&webp=true

fanlin returns lossless WebP image in following conditions.

• GET parameter quality=100 AND source image format is PNG / GIF / WebP

Limitations

• Do not support animations

Server-Timing Support

Add "use_server_timing": true at Global parameters in config file. You will get Server-Timing output. Be careful, your system architecture or perfomance will be exposed to enduser with Server-Timing output.

fanlin outputs following timings:

• f_load: The time for load source image.
• f_decode: The time for decode and format source image.
• f_encode: The time for encode to final image format.

Local test with Amazon S3 mock server

If you specify use_mock attribute as true in providers directive, fanlin behaves local access mode to refer a mock server compatible with Amazon S3.

{
    "port": 3000,
    "max_width": 2000,
    "max_height": 1000,
    "404_img_path": "img/404.png",
    "access_log_path": "/dev/stdout",
    "error_log_path": "/dev/stderr",
    "max_clients": 50,
    "providers": [
        {
            "/foo": {
                "type": "s3",
                "src": "s3://local-test/images",
                "region": "ap-northeast-1",
                "norm_form": "nfd",
                "use_mock": true
            }
        },
        {
            "/bar": {
                "type": "web",
                "src": "http://localhost:3000/foo"
            }
        },
        {
            "/baz": {
                "type": "local",
                "src": "img"
            }
        }

    ]
}

Also, It requires booting the mock server in advance.

$ docker compose up
$ make create-s3-bucket
$ make copy-object SRC=img/Lenna.jpg DEST=images/Lenna.jpg
$ make run

Now you can test fanlin locally.

$ curl -I 'http://localhost:3000/foo/Lenna.jpg?w=300&h=200&rgb=64,64,64'
$ curl -I 'http://localhost:3000/bar/Lenna.jpg?w=300&h=200&rgb=64,64,64'
$ curl -I 'http://localhost:3000/baz/Lenna.jpg?w=300&h=200&rgb=64,64,64'

LICENSE

Written in Go and licensed under the MIT License, it can also be used as a library.