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Fast, secure image processing server and Go library, using libvips

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Quick Overview

Imagor is a fast, Docker-ready image processing server written in Go. It's designed to be a high-performance, on-demand image manipulation and optimization service, capable of handling a wide range of image operations including resizing, cropping, and various filters.

Pros

  • High performance and scalability due to its Go implementation
  • Extensive image manipulation capabilities (resize, crop, filters, etc.)
  • Easy deployment with Docker support
  • Compatible with Thumbor's URL structure, making it a drop-in replacement

Cons

  • Limited documentation compared to some more established alternatives
  • Fewer built-in storage options compared to Thumbor
  • May require additional setup for advanced features or custom integrations
  • Relatively newer project, which might mean less community support

Code Examples

  1. Basic image resizing:
import "github.com/cshum/imagor"

loader := imagor.NewHTTPLoader()
processor := imagor.NewProcessor()

result, err := processor.Process(ctx, loader, imagor.Params{
    Image: "https://example.com/image.jpg",
    Width: 300,
    Height: 200,
})
  1. Applying filters:
result, err := processor.Process(ctx, loader, imagor.Params{
    Image: "https://example.com/image.jpg",
    Filters: []imagor.Filter{
        {Name: "brightness", Args: []interface{}{10}},
        {Name: "contrast", Args: []interface{}{15}},
    },
})
  1. Cropping and resizing:
result, err := processor.Process(ctx, loader, imagor.Params{
    Image:  "https://example.com/image.jpg",
    Width:  300,
    Height: 200,
    CropMode: imagor.CropModeSmartCrop,
    Fit:      imagor.FitCover,
})

Getting Started

To get started with Imagor, follow these steps:

  1. Install Imagor:

    go get github.com/cshum/imagor

  2. Create a basic server:

    package main

import (
    "github.com/cshum/imagor"
    "github.com/cshum/imagor/imagorpath"
)

func main() {
    app := imagor.New(
        imagor.WithLoaders(imagor.NewHTTPLoader()),
        imagor.WithProcessors(imagor.NewProcessor()),
    )
    server := imagorpath.NewServer(app)
    server.ListenAndServe(":8000")
}

  3. Run the server and access images using Thumbor-compatible URLs:

    http://localhost:8000/300x200/filters:brightness(10):contrast(15)/https://example.com/image.jpg

Competitor Comparisons

thumbor logo

thumbor

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thumbor is an open-source photo thumbnail service by globo.com

Pros of Thumbor

  • More mature and widely adopted project with a larger community
  • Extensive documentation and broader feature set
  • Supports multiple storage backends and caching mechanisms

Cons of Thumbor

  • Written in Python, which may have performance limitations compared to Go
  • Can be more complex to set up and configure
  • Larger resource footprint

Code Comparison

Thumbor (Python):

from thumbor.handlers.imaging import ImagingHandler

class MyHandler(ImagingHandler):
    def get(self):
        # Custom image processing logic
        super(MyHandler, self).get()

Imagor (Go):

package main

import "github.com/cshum/imagor"

func main() {
    srv := imagor.New()
    srv.Use(imagor.NewProcessor())
    srv.ListenAndServe(":8000")
}

Key Differences

  • Thumbor offers more built-in features and flexibility, while Imagor focuses on simplicity and performance
  • Imagor is written in Go, which can provide better performance and lower resource usage
  • Thumbor has a more extensive plugin ecosystem, whereas Imagor has a more streamlined approach
  • Imagor's API is designed to be compatible with Thumbor, making migration easier

Both projects aim to provide efficient image processing and serving capabilities, with Thumbor offering more features and Imagor prioritizing performance and simplicity.

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Pros of Imaginary

  • Written in Go, potentially offering better performance and concurrency
  • Supports a wider range of image processing operations, including face detection and smart cropping
  • Provides a Docker image for easy deployment

Cons of Imaginary

  • More complex setup and configuration compared to Imagor
  • Larger codebase, which may lead to a steeper learning curve
  • Fewer built-in caching options

Code Comparison

Imaginary (main.go):

func main() {
    opts := ServerOptions{
        Port:               9000,
        CORS:               false,
        EnableURLSource:    true,
        EnablePlaceholder:  true,
        EnableURLSignature: true,
    }
    server := NewServer(opts)
    server.Listen()
}

Imagor (main.go):

func main() {
    app := imagor.New()
    app.Use(imagor.LoaderURL())
    app.Use(imagor.ProcessorImage())
    app.Use(imagor.ServerImage())
    app.Run(":8000")
}

Both projects offer powerful image processing capabilities, but Imaginary provides more advanced features at the cost of increased complexity. Imagor focuses on simplicity and ease of use, making it a good choice for projects with straightforward image processing needs. The code comparison shows that Imaginary requires more configuration options, while Imagor has a more streamlined setup process.

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Pros of imageproxy

  • Written in Go, potentially offering better performance and concurrency
  • Supports a wider range of image processing operations, including rotation and smart cropping
  • More flexible caching options, including support for various backends like Amazon S3 and Google Cloud Storage

Cons of imageproxy

  • Less actively maintained, with fewer recent updates compared to imagor
  • Lacks some advanced features present in imagor, such as lazy loading and watermarking
  • May have a steeper learning curve for configuration and deployment

Code Comparison

imageproxy:

func (p *Proxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    if r.URL.Path == "/favicon.ico" {
        http.Error(w, "404 Not Found", http.StatusNotFound)
        return
    }
    // ... (additional code)
}

imagor:

func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    ctx := r.Context()
    start := time.Now()
    defer func() {
        s.metrics.Latency.Observe(time.Since(start).Seconds())
    }()
    // ... (additional code)
}

Both projects implement image processing servers, but they differ in their approach and feature sets. imageproxy offers a broader range of image operations and flexible caching, while imagor provides more advanced features and active development. The choice between them depends on specific project requirements and preferences.

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An image resizing server written in Go

Pros of picfit

  • Written in Go, potentially offering better performance and concurrency
  • Supports multiple storage backends (File System, Amazon S3, Google Cloud Storage)
  • Includes a built-in HTTP server for serving processed images

Cons of picfit

  • Less actively maintained (last commit over 2 years ago)
  • Fewer image processing operations compared to imagor
  • Limited documentation and examples

Code Comparison

imagor (Python):

from imagor import imagor

app = imagor()
app.run(host='0.0.0.0', port=8000)

picfit (Go):

package main

import "github.com/thoas/picfit"

func main() {
    picfit.Run()
}

Both projects aim to provide image processing and serving capabilities, but they differ in implementation language and feature sets. imagor is written in Python and offers a wider range of image processing operations, while picfit is implemented in Go and focuses on performance and multiple storage backend support.

imagor has more recent development activity and better documentation, making it potentially easier to adopt and integrate. However, picfit's Go implementation may provide better performance for high-load scenarios.

The code comparison shows that both projects offer simple ways to start the image processing server, with imagor providing more configuration options directly in the startup code.

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Pros of flyimg

  • Built with PHP and Symfony, which may be more familiar to some developers
  • Supports a wider range of image processing operations out-of-the-box
  • Includes a built-in security layer with signing requests

Cons of flyimg

  • Less actively maintained compared to imagor
  • May have higher resource requirements due to PHP runtime
  • Fewer deployment options and less cloud-native focus

Code Comparison

imagor:

func (p *ImageProcessor) Resize(img image.Image, width, height int) image.Image {
    return resize.Resize(uint(width), uint(height), img, resize.Lanczos3)
}

flyimg:

public function resize(Image $image, int $width, int $height): Image
{
    return $image->resize($width, $height);
}

Both projects offer similar core functionality for image processing, but their implementations differ based on the programming languages used. imagor is written in Go, which may provide better performance and lower resource usage, while flyimg uses PHP, which might be more accessible to web developers familiar with the LAMP stack.

imagor focuses on being a lightweight, cloud-native solution with easy deployment options, while flyimg offers a more comprehensive set of image manipulation features out-of-the-box. The choice between the two may depend on specific project requirements, team expertise, and infrastructure preferences.

imgproxy logo

imgproxy

8,738

Fast and secure standalone server for resizing and converting remote images

Pros of imgproxy

  • Written in Go, offering potentially better performance and lower resource usage
  • Supports a wider range of image processing operations, including face detection and watermarking
  • More actively maintained with frequent updates and releases

Cons of imgproxy

  • More complex setup and configuration compared to imagor
  • Requires separate installation of libvips and other dependencies
  • May have a steeper learning curve for newcomers to image processing

Code Comparison

imagor configuration example:

ALLOWED_SOURCES = ['http://example.com/']
MAX_WIDTH = 1000
MAX_HEIGHT = 1000

imgproxy configuration example:

IMGPROXY_KEY=your_key
IMGPROXY_SALT=your_salt
IMGPROXY_MAX_SRC_RESOLUTION=50

Key Differences

  • imagor is Python-based, while imgproxy is Go-based
  • imagor follows the Thumbor API, making it easier to migrate from Thumbor
  • imgproxy offers more advanced features like automatic format conversion and WebP support
  • imagor has a simpler setup process, especially for Python developers
  • imgproxy may have better performance for high-volume image processing tasks

Both projects aim to provide efficient image processing and serving capabilities, but they cater to different use cases and developer preferences. The choice between them depends on specific project requirements, existing infrastructure, and team expertise.

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README

imagor

Test Status Coverage Status Docker Hub GitHub Container Registry Go Reference

imagor is a fast, secure image processing server and Go library.

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 implements libvips streaming that facilitates parallel processing pipelines, achieving high network throughput.

imagor features a ton of image processing use cases, available as a HTTP server with first-class Docker support. It adopts the thumbor URL syntax representing a high-performance drop-in replacement.

imagor is a Go library built with speed, security and extensibility in mind. Alongside there is imagorvideo bringing video thumbnail capability through ffmpeg C bindings.

Quick Start

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

Original images:

https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
https://raw.githubusercontent.com/cshum/imagor/master/testdata/dancing-banana.gif
https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher-front.png

Try out the following image URLs:

http://localhost:8000/unsafe/fit-in/200x200/filters:fill(white)/https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
http://localhost:8000/unsafe/200x200/smart/filters:fill(white):format(jpeg):quality(80)/https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
http://localhost:8000/unsafe/fit-in/-180x180/10x10/filters:hue(290):saturation(100):fill(yellow)/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png
http://localhost:8000/unsafe/30x40:100x150/filters:fill(cyan)/raw.githubusercontent.com/cshum/imagor/master/testdata/dancing-banana.gif
http://localhost:8000/unsafe/fit-in/200x150/filters:fill(yellow):watermark(raw.githubusercontent.com/cshum/imagor/master/testdata/gopher-front.png,repeat,bottom,0,40,40)/raw.githubusercontent.com/cshum/imagor/master/testdata/dancing-banana.gif

Image 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:IxJ/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. Coordinates can also be provided as float values between 0 and 1 (percentage of image dimensions)
  • 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:IxJ add left-top padding GxH and right-bottom padding IxJ
  • 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 path or URI
    • For image URI that contains ? character, this will interfere the URL query and should be encoded with encodeURIComponent or equivalent

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
      • If color is "none" - the filling would become fully transparent
  • focal(AxB:CxD) or focal(X,Y) adds a focal region or focal point for custom transformations:
    • Coordinated by a region of left-top point AxB and right-bottom point CxD, or a point X,Y.
    • Also accepts float values between 0 and 1 that represents percentage of image dimensions.
  • format(format) specifies the output format of the image
    • format accepts jpeg, png, gif, webp, tiff, avif, jp2
  • 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
  • label(text, x, y, size, color[, alpha[, font]]) adds a text label to the image. It can be positioned inside the image with the alignment specified, color and transparency support:
    • text text label, also support url encoded text.
    • x horizontal position that the text label will be in:
      • Positive number indicate position from the left, negative number from the right.
      • Number followed by a p e.g. 20p means calculating the value from the image width as percentage
      • left,right,center align left, right or centered respectively
    • y vertical position that the text label will be in:
      • Positive number indicate position from the top, negative number from the bottom.
      • Number followed by a p e.g. 20p means calculating the value from the image height as percentage
      • top,bottom,center vertical align top, bottom or centered respectively
    • size - text label font size
    • color - color name or hexadecimal rgb expression without the “#” character
    • alpha - text label transparency, a number between 0 (fully opaque) and 100 (fully transparent).
    • font - text label font type
  • max_bytes(amount) automatically degrades the quality of the image until the image is under the specified amount of bytes
  • max_frames(n) limit maximum number of animation frames n to be loaded
  • orient(angle) rotates the image before resizing and cropping, according to the angle value
    • angle accepts 0, 90, 180, 270
  • page(num) specify page number for PDF, or frame number for animated image, starts from 1
  • dpi(num) specify the dpi to render at for PDF and SVG
  • proportion(percentage) scales image to the proportion percentage of the image dimension
  • 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
    • 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
  • strip_exif() removes Exif metadata from the resulting image
  • strip_icc() removes ICC profile information from the resulting image
  • strip_metadata() removes all metadata from the resulting image
  • 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 number indicate position from the left, negative number 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 number indicate position from the top, negative number 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

Utility Filters

These filters do not manipulate images but provide useful utilities to the imagor pipeline:

  • attachment(filename) returns attachment in the Content-Disposition header, and the browser will open a "Save as" dialog with filename. When filename not specified, imagor will get the filename from the image source
  • expire(timestamp) adds expiration time to the content. timestamp is the unix milliseconds timestamp, e.g. if content is valid for 30s then timestamp would be Date.now() + 30*1000 in JavaScript.
  • preview() skips the result storage even if result storage is enabled. Useful for conditional caching
  • raw() response with a raw unprocessed and unchecked source image. Image still loads from loader and storage but skips the result storage

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(s), Proxy, File System, AWS S3 and Google Cloud Storage. By default, HTTP Loader is used as fallback. You can choose to enable additional adaptors that fit your use cases.

File System

Docker Compose example 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_STORAGE_MKDIR_PERMISSION: 0755 # optional
      FILE_STORAGE_WRITE_PERMISSION: 0666 # optional

      FILE_RESULT_STORAGE_BASE_DIR: /mnt/data/result # enable file result storage by specifying base dir
      FILE_RESULT_STORAGE_MKDIR_PERMISSION: 0755 # optional
      FILE_RESULT_STORAGE_WRITE_PERMISSION: 0666 # optional
      
    ports:
      - "8000:8000"

AWS S3

Docker Compose example with AWS S3. Also works with S3 compatible such as MinIO, DigitalOcean Space.

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_STORAGE_ACL: public-read # optional - see https://docs.aws.amazon.com/AmazonS3/latest/userguide/acl-overview.html#canned-acl

      S3_RESULT_STORAGE_BUCKET: mybucket # enable S3 result storage by specifying bucket
      S3_RESULT_STORAGE_BASE_DIR: images/result # optional
      S3_RESULT_STORAGE_ACL: public-read # optional
    ports:
      - "8000:8000"
Custom S3 Endpoint

Configure custom S3 endpoint for S3 compatible such as MinIO, DigitalOcean Space:

      S3_ENDPOINT: http://minio:9000
      S3_FORCE_PATH_STYLE: 1

By default, S3 prepends bucket name as subdomain to the request URL:

http://mybucket.minio:9000/image.jpg

this may not be desirable for a self-hosted endpoint. You can also switch to path-style requests using S3_FORCE_PATH_STYLE=1 such that the host remains unchanged:

http://minio:9000/mybucket/image.jpg
Different AWS Credentials for S3 Loader, Storage and Result Storage

Set the following environment variables to override the global AWS Credentials for S3 Loader, Storage and Result Storage:

AWS_LOADER_REGION
AWS_LOADER_ACCESS_KEY_ID
AWS_LOADER_SECRET_ACCESS_KEY
S3_LOADER_ENDPOINT

AWS_STORAGE_REGION
AWS_STORAGE_ACCESS_KEY_ID
AWS_STORAGE_SECRET_ACCESS_KEY
S3_STORAGE_ENDPOINT

AWS_RESULT_STORAGE_REGION
AWS_RESULT_STORAGE_ACCESS_KEY_ID
AWS_RESULT_STORAGE_SECRET_ACCESS_KEY
S3_RESULT_STORAGE_ENDPOINT

Google Cloud Storage

Docker Compose example with Google Cloud Storage:

version: "3"
services:
  imagor:
    image: shumc/imagor:latest
    volumes:
      - ./googlesecret:/etc/secrets/google
    environment:
      PORT: 8000
      IMAGOR_SECRET: mysecret # secret key for URL signature
      GOOGLE_APPLICATION_CREDENTIALS: /etc/secrets/google/appcredentials.json # google cloud secrets file

      GCLOUD_LOADER_BUCKET: mybucket # enable loader by specifying bucket
      GCLOUD_LOADER_BASE_DIR: images # optional

      GCLOUD_STORAGE_BUCKET: mybucket # enable storage by specifying bucket
      GCLOUD_STORAGE_BASE_DIR: images # optional
      GCLOUD_STORAGE_ACL: publicRead # optional - see https://cloud.google.com/storage/docs/json_api/v1/objects/insert

      GCLOUD_RESULT_STORAGE_BUCKET: mybucket # enable result storage by specifying bucket
      GCLOUD_RESULT_STORAGE_BASE_DIR: images/result # optional
      GCLOUD_RESULT_STORAGE_ACL: publicRead # optional
    ports:
      - "8000:8000"

Storage and Result Storage Path Style

Storage and Result Storage path style enables additional hashing rules to the storage path when loading and saving images:

IMAGOR_STORAGE_PATH_STYLE=digest

  • foobar.jpg becomes e6/86/1a810ff186b4f747ef85f7c53946f0e6d8cb

IMAGOR_RESULT_STORAGE_PATH_STYLE=digest

  • fit-in/16x17/foobar.jpg becomes 61/4c/9ba1725e8cdd8263a4ad437c56b35f33deba

IMAGOR_RESULT_STORAGE_PATH_STYLE=suffix

  • 166x169/top/foobar.jpg becomes foobar.45d8ebb31bd4ed80c26e.jpg
  • 17x19/smart/example.com/foobar becomes example.com/foobar.ddd349e092cda6d9c729

IMAGOR_RESULT_STORAGE_PATH_STYLE=size

  • 166x169/top/foobar.jpg becomes foobar.45d8ebb31bd4ed80c26e_166x169.jpg
  • 17x19/smart/example.com/foobar becomes example.com/foobar.ddd349e092cda6d9c729_17x19

Security

URL Signature

In production environment, it is highly recommended turning off IMAGOR_UNSAFE and setting up URL signature using IMAGOR_SECRET, to prevent DDoS attacks that abuse multiple image operations.

The URL signature hash is based on SHA digest, created by taking the URL path (excluding /unsafe/) with secret. The hash is then Base64 URL encoded. An example in Node.js:

const crypto = require('crypto');

function sign(path, secret) {
  const hash = crypto.createHmac('sha1', secret)
          .update(path)
          .digest('base64')
          .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

Custom HMAC Signer

imagor uses SHA1 HMAC signer by default, the same one used by thumbor. However, SHA1 is not considered cryptographically secure. If that is a concern it is possible to configure different signing method and truncate length. imagor supports sha1, sha256, sha512 signer type:

IMAGOR_SIGNER_TYPE=sha256
IMAGOR_SIGNER_TRUNCATE=40

The Node.js example then becomes:

const crypto = require('crypto');

function sign(path, secret) {
  const hash = crypto.createHmac('sha256', secret)
          .update(path)
          .digest('base64')
          .slice(0, 40)
          .replace(/\+/g, '-').replace(/\//g, '_')
  return hash + '/' + path
}

console.log(sign('500x500/top/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png', 'mysecret'))
// IGEn3TxngivD0jy4uuiZim2bdUCvhcnVi1Nm0xGy/500x500/top/raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png

Image Bombs Prevention

imagor checks the image type and its resolution before the actual processing happens. The processing will be rejected if the image dimensions are too big, which protects from so-called "image bombs". You can set the max allowed image resolution and dimensions using VIPS_MAX_RESOLUTION, VIPS_MAX_WIDTH, VIPS_MAX_HEIGHT:

VIPS_MAX_RESOLUTION=16800000
VIPS_MAX_WIDTH=5000
VIPS_MAX_HEIGHT=5000

Allowed Sources and Base URL

Whitelist specific hosts to restrict loading images only from the allowed sources using HTTP_LOADER_ALLOWED_SOURCES or HTTP_LOADER_ALLOWED_SOURCE_REGEXP.

  • HTTP_LOADER_ALLOWED_SOURCES accepts csv wth glob pattern e.g.:

    HTTP_LOADER_ALLOWED_SOURCES=*.foobar.com,my.foobar.com,mybucket.s3.amazonaws.com

  • HTTP_LOADER_ALLOWED_SOURCE_REGEXP accepts a regular expression matching on the full URL e.g.:

    HTTP_LOADER_ALLOWED_SOURCE_REGEXP='^https://raw\.githubusercontent\.com/cshum/imagor/.*'

Alternatively, it is possible to set a base URL for loading images strictly from one HTTP source. This also trims down the base URL from image endpoint:

Example URL:

http://localhost:8000/unsafe/fit-in/200x150/filters:fill(yellow):watermark(raw.githubusercontent.com/cshum/imagor/master/testdata/gopher-front.png,repeat,bottom,0,40,40)/raw.githubusercontent.com/cshum/imagor/master/testdata/dancing-banana.gif

With HTTP Loader Base URL config:

HTTP_LOADER_BASE_URL=https://raw.githubusercontent.com/cshum/imagor/master

The example URL then becomes:

http://localhost:8000/unsafe/fit-in/200x150/filters:fill(yellow):watermark(testdata/gopher-front.png,repeat,bottom,0,40,40)/testdata/dancing-banana.gif

Metadata and Exif

imagor provides metadata endpoint that extracts information such as image format, resolution and Exif metadata. Under the hood, it tries to retrieve data just enough to extract the header, without reading and processing the whole image in memory.

To use the metadata endpoint, add /meta right after the URL signature hash before the image operations. Example:

http://localhost:8000/unsafe/meta/fit-in/50x50/raw.githubusercontent.com/cshum/imagor/master/testdata/Canon_40D.jpg

{
  "format": "jpeg",
  "content_type": "image/jpeg",
  "width": 50,
  "height": 34,
  "orientation": 1,
  "pages": 1,
  "bands": 3,
  "exif": {
    "ApertureValue": "368640/65536",
    "ColorSpace": 1,
    "ComponentsConfiguration": "Y Cb Cr -",
    "Compression": 6,
    "DateTime": "2008:07:31 10:38:11",
    "ISOSpeedRatings": 100,
    "Make": "Canon",
    "MeteringMode": 5,
    "Model": "Canon EOS 40D",
    //...
  }
}

Prepending /params to the existing endpoint returns the endpoint attributes in JSON form, useful for previewing the endpoint parameters. Example:

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

Go Library

imagor is a Go library built with speed, security and extensibility in mind. It facilitates high-level image processing in a modular architecture made up of a series of Go packages:

  • imagor - the imagor core library
  • imagorpath - parse and generate imagor endpoint
  • vips - libvips C bindings with imagor.Processor implementation
  • httploader - HTTP Loader, an imagor.Loader implementation
  • filestorage - File Storage, an imagor.Storage implementation
  • s3storage - AWS S3 Storage, an imagor.Storage implementation
  • gcloudstorage - Google Cloud Storage, an imagor.Storage implementation

Install libvips and enable CGO:

  • brew install vips for Mac
  • CGO_CFLAGS_ALLOW=-Xpreprocessor being set to compile Go

See example below and also examples folder for various ways you can use imagor:

package main

import (
	"context"
	"github.com/cshum/imagor"
	"github.com/cshum/imagor/imagorpath"
	"github.com/cshum/imagor/loader/httploader"
	"github.com/cshum/imagor/vips"
	"io"
	"os"
)

func main() {
	app := imagor.New(
		imagor.WithLoaders(httploader.New()),
		imagor.WithProcessors(vips.NewProcessor()),
	)
	ctx := context.Background()
	if err := app.Startup(ctx); err != nil {
		panic(err)
	}
	defer app.Shutdown(ctx)
	blob, err := app.Serve(ctx, imagorpath.Params{
		Image:  "https://raw.githubusercontent.com/cshum/imagor/master/testdata/gopher.png",
		Width:  500,
		Height: 500,
		Smart:  true,
		Filters: []imagorpath.Filter{
			{"fill", "white"},
			{"format", "jpg"},
		},
	})
	if err != nil {
		panic(err)
	}
	reader, _, err := blob.NewReader()
	if err != nil {
		panic(err)
	}
	defer reader.Close()
	file, err := os.Create("gopher.jpg")
	if err != nil {
		panic(err)
	}
	defer file.Close()
	if _, err := io.Copy(file, reader); err != nil {
		panic(err)
	}
}

Configuration

imagor supports command-line arguments and environment variables for the arguments equivalent in capitalized snake case, see available options imagor -h. For instances -imagor-secret would become IMAGOR_SECRET:

# both are equivalent

imagor -debug -imagor-secret 1234

DEBUG=1 IMAGOR_SECRET=1234 imagor

Configuration can also be specified in a .env environment variable file and referenced with the -config flag:

imagor -config path/to/config.env

config.env:

PORT=8000
IMAGOR_SECRET=mysecret
DEBUG=1

Available options

imagor -h
Usage of imagor:
  -debug
        Debug mode
  -port int
        Server port (default 8000)
  -version
        imagor version
  -config string
        Retrieve configuration from the given file (default ".env")

  -imagor-secret string
        Secret key for signing imagor URL
  -imagor-unsafe
        Unsafe imagor that does not require URL signature. Prone to URL tampering
  -imagor-auto-webp
        Output WebP format automatically if browser supports
  -imagor-auto-avif
        Output AVIF format automatically if browser supports (experimental)
  -imagor-base-params string
        imagor endpoint base params that applies to all resulting images e.g. filters:watermark(example.jpg)
  -imagor-signer-type string
        imagor URL signature hasher type: sha1, sha256, sha512 (default "sha1")
  -imagor-signer-truncate int
        imagor URL signature truncate at length
  -imagor-result-storage-path-style string
        imagor result storage path style: original, digest, suffix (default "original")
  -imagor-storage-path-style string
        imagor storage path style: original, digest (default "original")
  -imagor-cache-header-ttl duration
        imagor HTTP cache header ttl for successful image response (default 168h0m0s)
  -imagor-cache-header-swr duration
        imagor HTTP Cache-Control header stale-while-revalidate for successful image response (default 24h0m0s)
  -imagor-cache-header-no-cache
        imagor HTTP Cache-Control header no-cache for successful image response
  -imagor-request-timeout duration
        Timeout for performing imagor request (default 30s)
  -imagor-load-timeout duration
        Timeout for imagor Loader request, should be smaller than imagor-request-timeout
  -imagor-save-timeout duration
        Timeout for saving image to imagor Storage
  -imagor-process-timeout duration
        Timeout for image processing
  -imagor-process-concurrency int
        Maximum number of image process to be executed simultaneously. Requests that exceed this limit are put in the queue. Set -1 for no limit (default -1)
  -imagor-process-queue-size int
        Maximum number of image process that can be put in the queue. Requests that exceed this limit are rejected with HTTP status 429
  -imagor-base-path-redirect string
        URL to redirect for imagor / base path e.g. https://www.google.com
  -imagor-modified-time-check
        Check modified time of result image against the source image. This eliminates stale result but require more lookups
  -imagor-disable-params-endpoint
        imagor disable /params endpoint
  -imagor-disable-error-body
        imagor disable response body on error

  -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

  -prometheus-bind string
        Specify address and port to enable Prometheus metrics, e.g. :5000, prom:7000
  -prometheus-path string
        Prometheus metrics path (default "/")
        
  -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-base-url string
        HTTP Loader base URL that prepends onto existing image path. This overrides the default scheme option.
  -http-loader-forward-headers string
        Forward request header to HTTP Loader request by csv e.g. User-Agent,Accept
  -http-loader-override-response-headers string
        Override HTTP Loader response header to image response by csv e.g. Cache-Control,Expires
  -http-loader-forward-client-headers
        Forward browser client 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-allowed-source-regexp string
        HTTP Loader allowed hosts regexp to load images from if set. Combines as OR with allowed host glob pattern sources.
  -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-accept string
        HTTP Loader set request Accept header and validate response Content-Type header (default "*/*") 
  -http-loader-block-link-local-networks
        HTTP Loader rejects connections to link local network IP addresses.
  -http-loader-block-loopback-networks
        HTTP Loader rejects connections to loopback network IP addresses.
  -http-loader-block-private-networks
        HTTP Loader rejects connections to private network IP addresses.
  -http-loader-block-networks string
        HTTP Loader rejects connections to link local network IP addresses. This options takes a comma separated list of networks in CIDR notation e.g ::1/128,127.0.0.0/8.
  -http-loader-disable
        Disable HTTP Loader

  -file-safe-chars string
        File safe characters to be excluded from image key escape. Set -- for no-op
  -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-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")
  -file-result-storage-expiration duration
        File Result Storage expiration duration e.g. 24h. Default no expiration
  -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")
  -file-storage-expiration duration
        File Storage expiration duration e.g. 24h. Default no expiration

  -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
  -aws-session-token string
        AWS Session Token. Optional temporary credentials token
  -s3-endpoint string
        Optional S3 Endpoint to override default
  -s3-safe-chars string
        S3 safe characters to be excluded from image key escape. Set -- for no-op
  -s3-force-path-style
        S3 force the request to use path-style addressing s3.amazonaws.com/bucket/key, instead of bucket.s3.amazonaws.com/key
  -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-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")
  -s3-result-storage-expiration duration
        S3 Result Storage expiration duration e.g. 24h. Default no expiration
  -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")
  -s3-storage-expiration duration
        S3 Storage expiration duration e.g. 24h. Default no expiration
        
  -aws-loader-access-key-id string
        AWS Access Key ID for S3 Loader to override global config
  -aws-loader-region string
        AWS Region for S3 Loader to override global config
  -aws-loader-secret-access-key string
        AWS Secret Access Key for S3 Loader to override global config
  -aws-loader-session-token string
        AWS Session Token for S3 Loader to override global config
  -s3-loader-endpoint string
        Optional S3 Loader Endpoint to override default
  -aws-storage-access-key-id string
        AWS Access Key ID for S3 Storage to override global config
  -aws-storage-region string
        AWS Region for S3 Storage to override global config
  -aws-storage-secret-access-key string
        AWS Secret Access Key for S3 Storage to override global config
  -aws-storage-session-token string
        AWS Session Token for S3 Storage to override global config
  -s3-storage-endpoint string
        Optional S3 Storage Endpoint to override default
  -aws-result-storage-access-key-id string
        AWS Access Key ID for S3 Result Storage to override global config
  -aws-result-storage-region string
        AWS Region for S3 Result Storage to override global config
  -aws-result-storage-secret-access-key string
        AWS Secret Access Key for S3 Result Storage to override global config
  -aws-result-storage-session-token string
        AWS Session Token for S3 Result Storage to override global config
  -s3-result-storage-endpoint string
        Optional S3 Storage Endpoint to override default

  -gcloud-safe-chars string
        Google Cloud safe characters to be excluded from image key escape. Set -- for no-op
  -gcloud-loader-base-dir string
        Base directory for Google Cloud Loader
  -gcloud-loader-bucket string
        Bucket name for Google Cloud Storage Loader. Enable Google Cloud Loader only if this value present
  -gcloud-loader-path-prefix string
        Base path prefix for Google Cloud Loader
  -gcloud-result-storage-acl string
        Upload ACL for Google Cloud Result Storage
  -gcloud-result-storage-base-dir string
        Base directory for Google Cloud Result Storage
  -gcloud-result-storage-bucket string
        Bucket name for Google Cloud Result Storage. Enable Google Cloud Result Storage only if this value present
  -gcloud-result-storage-expiration duration
        Google Cloud Result Storage expiration duration e.g. 24h. Default no expiration
  -gcloud-result-storage-path-prefix string
        Base path prefix for Google Cloud Result Storage
  -gcloud-storage-acl string
        Upload ACL for Google Cloud Storage
  -gcloud-storage-base-dir string
        Base directory for Google Cloud
  -gcloud-storage-bucket string
        Bucket name for Google Cloud Storage. Enable Google Cloud Storage only if this value present
  -gcloud-storage-expiration duration
        Google Cloud Storage expiration duration e.g. 24h. Default no expiration
  -gcloud-storage-path-prefix string
        Base path prefix for Google Cloud Storage
        
  -vips-max-animation-frames int
        VIPS maximum number of animation frames to be loaded. Set 1 to disable animation, -1 for unlimited
  -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-filter-ops int
        VIPS maximum number of filter operations allowed. Set -1 for unlimited (default -1)
  -vips-max-width int
        VIPS max image width
  -vips-max-height int
        VIPS max image height
  -vips-max-resolution int
        VIPS max image resolution
  -vips-mozjpeg
        VIPS enable maximum compression with MozJPEG. Requires mozjpeg to be installed
  -vips-avif-speed int
        VIPS avif speed, the lowest is at 0 and the fastest is at 9 (Default 5).
  -vips-strip-metadata
        VIPS strips all metadata from the resulting image