Caddy Image Processor

This repository contains a CaddyServer module for processing images on the fly using libvips.

Features

• Automatic image processing based on URL query parameters
• Supports resizing, rotating, cropping, quality adjustments, format conversion, and more
• Efficient processing using libvips

Prerequisites

• libvips installed on your system
• libvips-dev installed on your system (only for xcaddy build)

Installation and Configuration

Using Docker

• Pull the Docker image from the GitHub Container Registry:

  docker pull ghcr.io/quix-labs/caddy-image-processor:latest

Using xcaddy

• Before building the module, ensure you have xcaddy installed on your system. You can install it using the following command:

  go install github.com/caddyserver/xcaddy/cmd/xcaddy@latest

• To build this module into Caddy, run the following command:

  CGO_ENABLED=1 xcaddy build --with github.com/quix-labs/caddy-image-processor

  This command compiles Caddy with the image processing module included.

Using prebuilt assets

• You can also install the tool using release assets.

  Download the appropriate package from the Releases page, and then follow the instructions provided for your specific platform.

Usage

Using Docker

docker run -p 80:80 -v $PWD/Caddyfile:/etc/caddy/Caddyfile -d ghcr.io/quix-labs/caddy-image-processor:latest

Your can see more information in the official docker documentation for caddy

Using xcaddy build / prebuilt assets

/path/to/your/caddy run --config /etc/caddy/Caddyfile

Your can see more information in the official documentation for caddy

Example Caddyfile

Using file_server

localhost {
    root /your-images-directory
    file_server
    image_processor
}

Using reverse_proxy

localhost {
    reverse_proxy your-domain.com
    image_processor
}

In this example, all requests undergo processing by the image processor module before being served by the caddy.

Available Query Parameters

Param	Name	Description	Type
h	Height	Image height	Integer
w	Width	Image width	Integer
ah	AreaHeight	Area height	Integer
aw	AreaWidth	Area width	Integer
t	Top	Y-coordinate of the top-left corner	Integer
l	Left	X-coordinate of the top-left corner	Integer
q	Quality	Image quality (JPEG compression)	Integer (default 75)
cp	Compression	Compression level (0-9, 0 = lossless)	Integer
z	Zoom	Zoom level	Integer
crop	Crop	Whether cropping is enabled	Boolean
en	Enlarge	Whether enlargement is enabled	Boolean
em	Embed	Whether embedding is enabled	Boolean
flip	Flip	Whether vertical flipping is enabled	Boolean
flop	Flop	Whether horizontal flipping is enabled	Boolean
force	Force	Whether to force action	Boolean
nar	NoAutoRotate	Whether auto-rotation is disabled	Boolean
np	NoProfile	Whether profile is disabled	Boolean
itl	Interlace	Whether interlacing is enabled	Boolean (default true)
smd	StripMetadata	Whether to strip metadata	Boolean (default true)
tr	Trim	Whether trimming is enabled	Boolean
ll	Lossless	Whether compression is lossless	Boolean
th	Threshold	Color threshold	Float
g	Gamma	Gamma correction	Float
br	Brightness	Brightness	Float
c	Contrast	Contrast	Float
r	Rotate	Rotation angle (45, 90, 135, 180, 235, 270, 315)	Integer
b	GaussianBlur	Gaussian blur level	Integer
bg	Background	Background color (white, black, red, magenta, blue, cyan, green, yellow, or hexadecimal format #RRGGBB)	Color
fm	Type	Image type (jpg, png, gif, webp, avif)	Image Type (default original)

Examples

• Resize an image to a width of 400 pixels and a height of 300 pixels:
  • http://example.com/image.jpg?w=400&h=300
• Crop an image to a width of 200 pixels and a height of 150 pixels starting from the top-left corner (x=50, y=50):
  • http://example.com/image.jpg?w=200&h=150&t=50&l=50&crop=true
• Adjust the quality of the image to 80:
  • http://example.com/image.jpg?q=80
• Convert an image to PNG format and apply a Gaussian blur of 5:
  • http://example.com/image.jpg?fm=png&b=5
• Rotate an image by 180 degrees and flip it horizontally:
  • http://example.com/image.jpg?r=180&flop=true
• Apply a color threshold of 0.5 and adjust the brightness to -10:
  • http://example.com/image.jpg?th=0.5&br=-10
• Convert an image to AVIF format with lossless compression:
  • http://example.com/image.jpg?fm=avif&ll=true

Advanced Configuration

This configuration allows you to control error handling with on_fail and on_security_fail.

You can also manage query parameter processing using allowed_params and disallowed_params.

This gives you fine-grained control over image processing in your Caddy server.

Example with on_fail and Security Configuration

localhost:80 {
    root test-dataset
    file_server
	
    image_processor {
	    
        # Serve original image if image in unprocessable
        on_fail bypass	    
        
        # Return 500 Internal Server Error if processing fails
        # on_fail abort	    
        
        security {

            # Use ignore to remove param from processing, all valid param are processed
            on_security_fail ignore

            # Use abort to return 400 Bad Request when fails
            # on_security_fail abort

            # Use bypass to serve original image without processing
            # on_security_fail bypass

            # Explicitely disable rotate capabilities
            disallowed_params r
            
            # As an alternative use this to only accept width and height processing 
            # allowed_params w h 
            
            constraints {
                h range 60 480

                w {
                    values 60 130 240 480 637

                    # Shortcut range 60 637
                    range {
                        from 60
                        to 637
                    }
                }
            }
        }
    }
}

Explanation:

• on_fail:

  • bypass (default value): If any error occurs, the original, unprocessed image will be returned.
  • abort: If an error occurs, a 500 Internal Server Error response will be returned.

• on_security_fail:

  • ignore (default value): If any security checks fail, they are ignored, and the image processing continues.
  • bypass: If any security checks fail, the original, unprocessed image will be returned.
  • abort: If any security checks fail, a 400 Bad Request response will be returned.

• Security Configuration (disallowed_params vs allowed_params):

  • disallowed_params: Specifies which query parameters are not allowed.

    For example, parameters like w (width) and r (rotation) can be restricted.

  • allowed_params: Specify which query parameters are allowed. As an alternative to disallowed_params.

  • Important: You cannot use both allowed_params and disallowed_params in the same configuration.

  • constraints: You san specify constraints for each parameter (see example)

Planned Features

The following features are planned for future implementation:

• Sharp compliance: fit,...

Development

To contribute to the development of Caddy Image Processor, follow these steps:

1. Make sure you have Go installed on your system.

2. Clone this repository to your local machine:

   git clone https://github.com/quix-labs/caddy-image-processor.git

3. Navigate to the project directory:

4. Install xcaddy if you haven't already:

   go get -u github.com/caddyserver/xcaddy/cmd/xcaddy

5. Make your changes in the source code.

6. Run tests to ensure your changes haven't introduced any issues:

   make test

7. If tests pass, you can build the project:

   make build

8. To run the project in development mode, use the following command:

   make run

9. Once you're satisfied with your changes, create a pull request to the main branch of the repository for review.

Credits

• COLANT Alan
• All Contributors

License

The MIT License (MIT). Please see License File for more information.