Imagor
Imagor is a fast, Docker-ready image processing server written in Go.
Imagor uses one of the most efficient image processing library libvips (with govips). It is typically 4-8x faster than using the quickest ImageMagick and GraphicsMagick settings.
Imagor is a Go library that is easily extensible, 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/golang-samples/gopher-vector/master/gopher.png
https://raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher-front.png
http://localhost:8000/unsafe/500x500/top/https://raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png
http://localhost:8000/unsafe/fit-in/500x500/filters:fill(white):format(jpeg)/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png
http://localhost:8000/unsafe/fit-in/-500x500/10x10/filters:hue(290):saturation(100):fill(yellow):format(jpeg):quality(80)/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png
http://localhost:8000/unsafe/fit-in/800x800/filters:fill(white):watermark(raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher-front.png,repeat,bottom,10):format(jpeg)/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png
Docker Compose Example
Imagor with File Loader and Storage 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
ports:
- "8000:8000"
Imagor with AWS S3 Loader and Storage:
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 loader bucket
S3_LOADER_BASE_DIR: images # optional
S3_STORAGE_BUCKET: mybucket # enable S3 storage by specifying storage bucket
S3_STORAGE_BASE_DIR: images # optional
ports:
- "8000:8000"
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
HASHis the URL Signature hash, orunsafeif unsafe mode is usedtrimremoves surrounding space in images using top-left pixel colorAxB:CxDmeans manually crop the image at left-top pointAxBand right-bottom pointCxDfit-inmeans that the generated image should not be auto-cropped and otherwise just fit in an imaginary box specified byExFstretchmeans resize the image toExFwithout keeping its aspect ratios-Ex-Fmeans resize the image to beExFof width per height size. The minus signs mean flip horizontally and verticallyGxHadd horizontal paddingGand vertical paddingHunderfit-inHALIGNis horizontal alignment of crop. Acceptsleft,rightorcenter, defaults tocenterVALIGNis vertical alignment of crop. Acceptstop,bottomormiddle, defaults tomiddlesmartmeans using smart detection of focal pointsfiltersa pipeline of image filter operations to be applied, see filters sectionIMAGEis the image URI
Imagor provides utilities for previewing and generating Imagor endpoint URI:
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/golang-samples/gopher-vector/master/gopher.png
{
"path": "fit-in/500x400/0x20/filters:fill(white)/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png",
"image": "raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png",
"hash": "g5bMqZvxaQK65qFPaP1qlJOTuLM=",
"fit_in": true,
"width": 500,
"height": 400,
"v_padding": 20,
"filters": [
{
"name": "fill",
"args": "white"
}
]
}
imagorpath package
Imagor Go library provides a imagorpath package which allows you to parse and generate Imagor endpoint using the Params struct:
import "github.com/cshum/imagor/imagorpath"
...
func Test(t *testing.T) {
params := imagorpath.Params{
Image: "raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png",
FitIn: true,
Width: 500,
Height: 400,
VPadding: 20,
Filters: imagorpath.Filters{
{
Name: "fill",
Args: "white",
},
},
}
// generate signed Imagor endpoint from Params struct with secret
path := imagorpath.Generate(params, "mysecret")
assert.Equal(t, path, "g5bMqZvxaQK65qFPaP1qlJOTuLM=/fit-in/500x400/0x20/filters:fill(white)/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png")
}
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 digest, created by taking the URL path (excluding /unsafe/) with secret. The hash is then base64url-encoded. An example in Go:
func SignPath(path, secret string) string {
h := hmac.New(sha1.New, []byte(secret))
h.Write([]byte(strings.TrimPrefix(path, "/")))
hash := base64.URLEncoding.EncodeToString(h.Sum(nil))
return hash + "/" + path
}
func main() {
fmt.Println(SignPath("500x500/top/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png", "mysecret"))
// RArq3FZw_bqxLcpKo1WI0aX_q7s=/fit-in/500x500/filters:fill(white):format(jpeg)/raw.githubusercontent.com/golang-samples/gopher-vector/master/gopher.png
}
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/golang-samples/gopher-vector/master/gopher-front.png,repeat,bottom,10):format(jpeg)/
Imagor supports the following filters:
background_color(color)sets the background color of a transparent imagecolorthe color name or hexadecimal rgb expression without the “#” character
blur(sigma)applies gaussian blur to the imagebrightness(amount)increases or decreases the image brightnessamount-100 to 100, the amount in % to increase or decrease the image brightness
contrast(amount)increases or decreases the image contrastamount-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 imageformataccepts jpeg, png, webp, gif, jp2, tiff
grayscale()changes the image to grayscalehue(angle)increases or decreases the image hueanglethe angle in degree to increase or decrease the hue rotation
quality(amount)changes the overall quality of the image, does nothing for pngamount0 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 100rotate(angle)rotates the given image according to the angle value passedangleaccepts 0, 90, 180, 270
round_corner(rx [, ry [, color]])adds rounded corners to the image with the specified color as backgroundrx,ryamount of pixel to use as radius. ry = rx if ry is not providedcolorthe color name or hexadecimal rgb expression without the “#” character
saturation(amount)increases or decreases the image saturationamount-100 to 100, the amount in % to increase or decrease the image saturation
sharpen(sigma)sharpens the imagetrim([tolerance [, position]])apply trim operation as part of the filter pipelinetolerancethe euclidean distance between the colors to get trimmed within the tolerance, default 1positiondefault usingtop-leftpixel color unless specifiedbottom-right
upscale()upscale the image iffit-inis usedwatermark(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 ratioimagewatermark image URI, using the same image loader configured for Imagorxhorizontal 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
pe.g. 20p means calculating the value from the image width as percentage left,right,centerpositioned left, right or centered respectivelyrepeatthe watermark will be repeated horizontally
yvertical 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
pe.g. 20p means calculating the value from the image height as percentage top,bottom,centerpositioned top, bottom or centered respectivelyrepeatthe watermark will be repeated vertically
alphawatermark image transparency, a number between 0 (fully opaque) and 100 (fully transparent).w_ratiopercentage of the width of the image the watermark should fit-inh_ratiopercentage of the height of the image the watermark should fit-in
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)
-imagor-secret string
Secret key for signing Imagor URL
-imagor-unsafe
Unsafe Imagor that does not require URL signature. Prone to URL tampering
-imagor-version
Imagor version
-imagor-cache-header-ttl duration
Imagor HTTP cache header ttl for successful image response (default 24h0m0s)
-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 (default 20s)
-imagor-save-timeout duration
Timeout for saving image for storage (default 1m0s)
-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
-vips-concurrency-level int
VIPS concurrency level. Default to the number of CPU cores.
-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 (default 10)
-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-default-scheme string
HTTP Loader default scheme if not specified by image path. Set "nil" to disable default scheme. (default "https")
-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-disable
Disable HTTP Loader
-file-loader-base-dir string
Base directory for File Loader. Will activate 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. Will activate 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-loader-base-dir string
Base directory for S3 Loader (default "/")
-s3-loader-bucket string
S3 Bucket for S3 Loader. Will activate S3 Loader only if this value present
-s3-loader-path-prefix string
Base path prefix for S3 Loader (default "/")
-s3-storage-base-dir string
Base directory for S3 Storage
-s3-storage-bucket string
S3 Bucket for S3 Storage. Will activate S3 Storage only if this value present
-s3-storage-path-prefix string
Base path prefix for S3 Storage
-s3-storage-acl string
Upload ACL for S3 Storage (default "public-read")
