Imagor

Imagor is a fast, Docker-ready image processing server written in Go.

Imagor uses one of the most efficient image processing library libvips. It is typically 4-8x faster than using the quickest ImageMagick and GraphicsMagick settings.

Imagor is a Go application that is highly optimized for concurrent requests, ready to be installed and used in any Unix environment, and ready to be containerized using Docker.

Imagor adopts the Thumbor URL syntax and covers most of the web image processing use cases. If these fit your requirements, Imagor would be a lightweight, high performance drop-in replacement.

Quick Start

docker run -p 8000:8000 shumc/imagor -imagor-unsafe

Try out the following image URLs:

# original images
https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher-front.png

http://localhost:8000/unsafe/500x500/top/https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
http://localhost:8000/unsafe/fit-in/500x500/filters:fill(white):format(jpeg)/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
http://localhost:8000/unsafe/fit-in/-500x500/10x10/filters:hue(290):saturation(100):fill(yellow):format(jpeg):quality(80)/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
http://localhost:8000/unsafe/fit-in/800x800/filters:fill(white):watermark(raw.githubusercontent.com/cshum/imagor/master/testdata/gopher-front.png,repeat,bottom,10):format(jpeg)/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png

Imagor Endpoint

Imagor endpoint is a series of URL parts which defines the image operations, followed by the image URI:

/HASH|unsafe/trim/AxB:CxD/fit-in/stretch/-Ex-F/GxH/HALIGN/VALIGN/smart/filters:NAME(ARGS):NAME(ARGS):.../IMAGE

HASH is the URL Signature hash, or unsafe if unsafe mode is used
trim removes surrounding space in images using top-left pixel color
AxB:CxD means manually crop the image at left-top point AxB and right-bottom point CxD
fit-in means that the generated image should not be auto-cropped and otherwise just fit in an imaginary box specified by ExF
stretch means resize the image to ExF without keeping its aspect ratios
-Ex-F means resize the image to be ExF of width per height size. The minus signs mean flip horizontally and vertically
GxH add horizontal padding G and vertical padding H
HALIGN is horizontal alignment of crop. Accepts left, right or center, defaults to center
VALIGN is vertical alignment of crop. Accepts top, bottom or middle, defaults to middle
smart means using smart detection of focal points
filters a pipeline of image filter operations to be applied, see filters section
IMAGE is the image URI

Imagor provides utilities for previewing and generating Imagor endpoint URI, including the imagorpath Go package and the /params endpoint:

`GET /params`

Prepending /params to the existing endpoint returns the endpoint attributes in JSON form, useful for preview:

curl http://localhost:8000/params/g5bMqZvxaQK65qFPaP1qlJOTuLM=/fit-in/500x400/0x20/filters:fill(white)/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png

{
  "path": "fit-in/500x400/0x20/filters:fill(white)/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png",
  "image": "raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png",
  "hash": "g5bMqZvxaQK65qFPaP1qlJOTuLM=",
  "fit_in": true,
  "width": 500,
  "height": 400,
  "v_padding": 20,
  "filters": [
    {
      "name": "fill",
      "args": "white"
    }
  ]
}

Filters

Filters /filters:NAME(ARGS):NAME(ARGS):.../ is a pipeline of image operations that will be sequentially applied to the image. Examples:

/filters:fill(white):format(jpeg)/
/filters:hue(290):saturation(100):fill(yellow):format(jpeg):quality(80)/
/filters:fill(white):watermark(raw.githubusercontent.com/cshum/imagor/master/testdata/gopher-front.png,repeat,bottom,10):format(jpeg)/

Imagor supports the following filters:

background_color(color) sets the background color of a transparent image
- color the color name or hexadecimal rgb expression without the “#” character
blur(sigma) applies gaussian blur to the image
brightness(amount) increases or decreases the image brightness
- amount -100 to 100, the amount in % to increase or decrease the image brightness
contrast(amount) increases or decreases the image contrast
- amount -100 to 100, the amount in % to increase or decrease the image contrast
fill(color) fill the missing area or transparent image with the specified color:
- color - color name or hexadecimal rgb expression without the “#” character
  - If color is "blur" - missing parts are filled with blurred original image.
  - If color is "auto" - the top left image pixel will be chosen as the filling color
format(format) specifies the output format of the image
- format accepts jpeg, png, webp, gif, jp2, tiff
grayscale() changes the image to grayscale
hue(angle) increases or decreases the image hue
- angle the angle in degree to increase or decrease the hue rotation
quality(amount) changes the overall quality of the image, does nothing for png
- amount 0 to 100, the quality level in %
rgb(r,g,b) amount of color in each of the rgb channels in %. Can range from -100 to 100
rotate(angle) rotates the given image according to the angle value passed
- angle accepts 0, 90, 180, 270
round_corner(rx [, ry [, color]]) adds rounded corners to the image with the specified color as background
- rx, ry amount of pixel to use as radius. ry = rx if ry is not provided
- color the color name or hexadecimal rgb expression without the “#” character
saturation(amount) increases or decreases the image saturation
- amount -100 to 100, the amount in % to increase or decrease the image saturation
sharpen(sigma) sharpens the image
trim([tolerance [, position]]) apply trim operation as part of the filter pipeline
- tolerance the euclidean distance between the colors to get trimmed within the tolerance, default 1
- position default using top-left pixel color unless specified bottom-right
upscale() upscale the image if fit-in is used
watermark(image, x, y, alpha [, w_ratio [, h_ratio]]) adds a watermark to the image. It can be positioned inside the image with the alpha channel specified and optionally resized based on the image size by specifying the ratio
- image watermark image URI, using the same image loader configured for Imagor
- x horizontal position that the watermark will be in:
  - Positive numbers indicate position from the left and negative numbers indicate position from the right.
  - Number followed by a p e.g. 20p means calculating the value from the image width as percentage
  - left,right,center positioned left, right or centered respectively
  - repeat the watermark will be repeated horizontally
- y vertical position that the watermark will be in:
  - Positive numbers indicate position from the top and negative numbers indicate position from the bottom.
  - Number followed by a p e.g. 20p means calculating the value from the image height as percentage
  - top,bottom,center positioned top, bottom or centered respectively
  - repeat the watermark will be repeated vertically
- alpha watermark image transparency, a number between 0 (fully opaque) and 100 (fully transparent).
- w_ratio percentage of the width of the image the watermark should fit-in
- h_ratio percentage of the height of the image the watermark should fit-in

Loader, Storage and Result Storage

Imagor Loader, Storage and Result Storage are the building blocks for loading and saving images from various sources:

Loader loads image. Enable Loader where you wish to load images from, but without modifying it e.g. static directory.
Storage loads and saves image. This allows subsequent requests for the same image loads directly from the storage, instead of HTTP source.
Result Storage loads and saves the processed image. This allows subsequent request of the same parameters loads from the result storage, saving processing resources.

Imagor provides built-in adaptors that support HTTP, proxy, file system and AWS S3. By default, HTTP Loader is used as fallback. You can choose to enable additional adaptors that fit your use cases.

Docker Compose Example

Imagor with file system, using mounted volume:

version: "3"
services:
  imagor:
    image: shumc/imagor:latest
    volumes:
      - ./:/mnt/data
    environment:
      PORT: 8000
      IMAGOR_UNSAFE: 1 # unsafe URL for testing

      FILE_LOADER_BASE_DIR: /mnt/data # enable file loader by specifying base dir

      FILE_STORAGE_BASE_DIR: /mnt/data # enable file storage by specifying base dir

      FILE_RESULT_STORAGE_BASE_DIR: /mnt/data/result # enable file result storage by specifying base dir
    ports:
      - "8000:8000"

Imagor with AWS S3:

version: "3"
services:
  imagor:
    image: shumc/imagor:latest
    environment:
      PORT: 8000
      IMAGOR_SECRET: mysecret # secret key for URL signature
      AWS_ACCESS_KEY_ID: ...
      AWS_SECRET_ACCESS_KEY: ...
      AWS_REGION: ...

      S3_LOADER_BUCKET: mybucket # enable S3 loader by specifying bucket
      S3_LOADER_BASE_DIR: images # optional

      S3_STORAGE_BUCKET: mybucket # enable S3 storage by specifying bucket
      S3_STORAGE_BASE_DIR: images # optional

      S3_RESULT_STORAGE_BUCKET: mybucket # enable S3 result storage by specifying bucket
      S3_RESULT_STORAGE_BASE_DIR: images/result # optional
    ports:
      - "8000:8000"

URL Signature

In production environment, it is highly recommended turning off IMAGOR_UNSAFE and setup IMAGOR_SECRET to avoid DDoS attacks that abuse multiple image operations.

The hash is based on HMAC SHA1 digest, created by taking the URL path (excluding /unsafe/) with secret. The hash is then base64url-encoded. An example in Node.js:

var hmacSHA1 = require("crypto-js/hmac-sha1")
var Base64 = require("crypto-js/enc-base64")

function sign(path, secret) {
  var hash = hmacSHA1(path, secret)
  hash = Base64.stringify(hash).replace(/\+/g, '-').replace(/\//g, '_')
  return hash + '/' + path
}

console.log(sign('500x500/top/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png', 'mysecret'))
// cST4Ko5_FqwT3BDn-Wf4gO3RFSk=/500x500/top/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png

Configurations

Imagor supports command-line arguments, see available options imagor -h. You may check main.go for better understanding the initialization sequences.

Imagor also supports environment variables or .env file for the arguments equivalent in capitalized snake case. For instances -imagor-secret would become IMAGOR_SECRET:

# both are equivalent

imagor -debug -imagor-secret=1234

DEBUG=1 IMAGOR_SECRET=1234 imagor

Available options:

imagor -h
Usage of imagor:
  -debug
        Debug mode
  -port int
        Sever port (default 8000)
  -version
        Imagor version

  -imagor-secret string
        Secret key for signing Imagor URL
  -imagor-unsafe
        Unsafe Imagor that does not require URL signature. Prone to URL tampering
  -imagor-cache-header-ttl duration
        Imagor HTTP cache header ttl for successful image response. Set -1 for no-cache (default 24h0m0s)
  -imagor-load-timeout duration
        Timeout for Imagor Loader request, should be smaller than imagor-request-timeout (default 20s)
  -imagor-process-timeout duration
        Timeout for image processing (default 20s)
  -imagor-request-timeout duration
        Timeout for performing Imagor request (default 30s)
  -imagor-save-timeout duration
        Timeout for saving image to Imagor Storage (default 20s)

  -server-address string
        Server address
  -server-cors
        Enable CORS
  -server-strip-query-string
        Enable strip query string redirection
  -server-path-prefix string
        Server path prefix
  -server-access-log
        Enable server access log

  -http-loader-allowed-sources string
        HTTP Loader allowed hosts whitelist to load images from if set. Accept csv wth glob pattern e.g. *.google.com,*.github.com.
  -http-loader-accept string
        HTTP Loader set request Accept header and validate response Content-Type header. Supports HTTP Accept header input e.g. image/*
  -http-loader-forward-headers string
        Forward request header to HTTP Loader request by csv e.g. User-Agent,Accept
  -http-loader-forward-all-headers
        Forward all request headers to HTTP Loader request
  -http-loader-insecure-skip-verify-transport
        HTTP Loader to use HTTP transport with InsecureSkipVerify true
  -http-loader-max-allowed-size int
        HTTP Loader maximum allowed size in bytes for loading images if set
  -http-loader-proxy-urls string
        HTTP Loader Proxy URLs. Enable HTTP Loader proxy only if this value present. Accept csv of proxy urls e.g. http://user:pass@host:port,http://user:pass@host:port
  -http-loader-proxy-allowed-sources string
        HTTP Loader Proxy allowed hosts that enable proxy transport, if proxy URLs are set. Accept csv wth glob pattern e.g. *.google.com,*.github.com.
  -http-loader-default-scheme string
        HTTP Loader default scheme if not specified by image path. Set "nil" to disable default scheme. (default "https")
  -http-loader-disable
        Disable HTTP Loader

  -file-safe-chars string
        File safe characters to be excluded from image key escape
        
  -file-loader-base-dir string
        Base directory for File Loader. Enable File Loader only if this value present
  -file-loader-path-prefix string
        Base path prefix for File Loader
        
  -file-storage-base-dir string
        Base directory for File Storage. Enable File Storage only if this value present
  -file-storage-path-prefix string
        Base path prefix for File Storage
  -file-storage-mkdir-permission string
        File Storage mkdir permission (default "0755")
  -file-storage-write-permission string
        File Storage write permission (default "0666")

  -aws-access-key-id string
        AWS Access Key ID. Required if using S3 Loader or S3 Storage
  -aws-region string
        AWS Region. Required if using S3 Loader or S3 Storage
  -aws-secret-access-key string
        AWS Secret Access Key. Required if using S3 Loader or S3 Storage
  -s3-endpoint string
        Optional S3 Endpoint to override default
  -s3-safe-chars string
        S3 safe characters to be excluded from image key escape

  -s3-loader-bucket string
        S3 Bucket for S3 Loader. Enable S3 Loader only if this value present
  -s3-loader-base-dir string
        Base directory for S3 Loader
  -s3-loader-path-prefix string
        Base path prefix for S3 Loader
        
  -s3-storage-bucket string
        S3 Bucket for S3 Storage. Enable S3 Storage only if this value present
  -s3-storage-base-dir string
        Base directory for S3 Storage
  -s3-storage-path-prefix string
        Base path prefix for S3 Storage
  -s3-storage-acl string
        Upload ACL for S3 Storage (default "public-read")

  -file-result-storage-base-dir string
        Base directory for File Result Storage. Enable File Result Storage only if this value present
  -file-result-storage-mkdir-permission string
        File Result Storage mkdir permission (default "0755")
  -file-result-storage-path-prefix string
        Base path prefix for File Result Storage
  -file-result-storage-write-permission string
        File Storage write permission (default "0666")

  -s3-result-storage-bucket string
        S3 Bucket for S3 Result Storage. Enable S3 Result Storage only if this value present
  -s3-result-storage-base-dir string
        Base directory for S3 Result Storage
  -s3-result-storage-path-prefix string
        Base path prefix for S3 Result Storage
  -s3-result-storage-acl string
        Upload ACL for S3 Result Storage (default "public-read")

  -vips-concurrency int
        VIPS concurrency. Set -1 to be the number of CPU cores (default 1)
  -vips-disable-blur
        VIPS disable blur operations for vips processor
  -vips-disable-filters string
        VIPS disable filters by csv e.g. blur,watermark,rgb
  -vips-max-cache-files int
        VIPS max cache files
  -vips-max-cache-mem int
        VIPS max cache mem
  -vips-max-cache-size int
        VIPS max cache size
  -vips-max-filter-ops int
        VIPS maximum number of filter operations allowed (default 10)
  -vips-max-height int
        VIPS max image height
  -vips-max-width int
        VIPS max image width

yiflylian/imagor