Name
    ngx_imaging_module - Dynamic image manipulation for arbitrary Nginx locations.
    
Status
    This module is in development. [beta]
    
Version
    0.0.1 - Initial internal release.
    
Synopsis
http {
    server {    
        
        location {
        
            error_page 404 = @img;
            recursive_error_pages on;
        }
            
        location @img {
            # try to create the image
            imaging "on";
            imaging_quality 70;       
            imaging_salt "Shared secrete hash salt";
            imaging_white_list "t400 t480"; 
            imaging_write_to_disk "on";     
        }
    }
}
    
Directives

    imaging
    syntax: imaging on|off
    default imaging off
    context: http, server, location

    imaging_salt 
    syntax: imaging_salt "my salt string";
    default ""
    context: http, server, location

    imaging_quality
    syntax: imaging_quality 70;
    default 70
    context: http, server, location
    
    imaging_white_list
    syntax: imaging_white_list "t200 t400 t400x400 r400";
    default ""
    context: http, server, location
    
    imaging_write_to_disk
    syntax: imaging_write_to_disk on|off;
    default on
    context: http, server, location
    

Description    
    ngx_imaging_module is an Nginx extension which allows you to create images 
    based on modifications to existing images. By delaying the generation of 
    transformed images until the time of request, your able to 'pay only for 
    what you eat'.

    Image transformations are encoded into the file name in a 'somewhat' human 
    readable form, where each transformation is separated by an underscore in the 
    filename.

    The module uses the GraphicsMagick 'core C API' to perform the various image 
    transformations. GraphicsMagick is a fork of ImageMagick which leverages
    OpenMP technologies to squeeze out more performance.


Security
    Shared salt key:
        - A salt is used in the creation of a hash string which is 
        passed from the calling application to the server to verify its 
        authenticity.
        

Image Transformations
    ngx_imaging_module currently supports the following transformations.
    
    Border
        Apply a border around an Image. 
        Examples:
            b5-black    - 5px Black border
            b1-red      - 1px Red border
            
    Crop
        Create a new image by cropping of the center of an existing image.
        Examples:
            c200
            c200x200
            cx200
    
    Scale
        Resize an image ignoring the aspect ratio.
        Examples:
            s200
            s200x200
            sx200
        
    Resize
        Resize an image preserving the aspect ratio.
            Examples:
            r200
            r200x200
            rx200
        
    Thumbnail
        Resize an image preserving the aspect ratio.
        Examples:
            t200
            t200x200
            tx200
    
    Note: These transformations can be chained together sperated by underscores.
    Example:
        t200_b1-black       - Thumbnail to 200 wide and add a 1px black border.
        r400x400_c200x200   - Resize to 400x400 then crop 200x200 out of that.
            

Installation
    Dependencies:
        GraphicMagick - Image manipulation library.
        
        Can be installed via normal Ubuntu apt-get:
            dev@box:~$ sudo apt-get install libmagickcore-dev 
	    # you may have to pull (libgraphicsmagick1-dev libgraphicsmagick3)

        Check that GraphicsMagic-config (build utilty program) is installed.
            dev@box:~$ GraphicsMagick-config --cppflags --ldflags --libs
        
        that should return something like:
            -I/usr/include/GraphicsMagick
            -L${exec_prefix}/lib
            -lGraphicsMagick -llcms -ltiff -lfreetype -ljasper -ljpeg -lpng -lwmflite -lXext -lSM -lICE -lX11 -lbz2 -lxml2 -lz -lm -lgomp -lpthread -lltdl
            
        OpenSSH - Contains SHA1 hash algorithm.
    
    Install:
        Download the modules source (either via bzr, or a source tarball).
        Then compile nginx as you would normally adding the following:
            --add-module=/path/to/ngx_imaging_module/
        
        Nginx will hook the config file located in that directory and use 
        it to pull in all the source files (as well as config the build).
    
Testing:
    Under /test