DIRECTORY.md

Directory configuration

There are few ways of setting the output directory for processed files. All of them work in the same way for resized, reduced and archived images.

Nothing

You are allowed to choose to do not setup any output directory configuration and use only prefix and/or suffix parameters. Just bare in mind that in such case all output files will be saved in same directory as input file -
S3 event notification limitations.

Directory

Parameter	Type	Required
directory	String	no

directory parameter should be a String representing output path. It could be an absolute (ie. output/) or relative (ie. ../output/, ./output) path. If you decide to use relative path, bare in mind that this could lead to situation where all output files will be saved in same directory structure as input file - S3 event notification limitations.

Template

Parameter	Type	Required
template	Object	no

template parameter is a Map with two keys: pattern and output, ie.:

{
    template: {
        pattern: "*path/c",
        output: "*path/d"
    }
}

pattern defines a pattern that describe path of input file directory. It's used for matching and and parsing, which allows you to store parts of parsed input directory as variables. More details in Syntax section.

In case the input file directory will not match the pattern, it will be skipped and the directory parameter will be processed, if present.

output defines a pattern that describe output directory path. It allows you to reuse variables parsed from input directory, like in example above. More details in Syntax section.

If you decide to use template parameter, bare in mind to avoid situation where output files will be saved in same directory structure as input file - S3 event notification limitations.

Template syntax

Source: path-template

The characters :, *, (, and ) have special meanings.

: indicates the following segment is the name of a variable * indicates the following segment is the splat/glob ( starts an optional segment ) ends an optional segment

additionally / and . will start a new segment.

Static Segments

"/foo/bar.baz"
 ^   ^   ^
 |   |   Starts a segment, matching ".baz"
 |   |
 |   Starts a segment, matching "/bar"
 |
 Starts a segment, matching "/foo"

Variables

"/foo/:bar.baz"
 ^    ^   ^
 |    |   Starts a new segment, that matches ".baz"
 |    |
 |    Matches anything up to the start of the next segment, with the value
 |    being stored in the "bar" parameter of the returned match object
 |
 Starts a segment, matching "/foo"

Splat/Glob

"/foo/*bar"
 ^    ^
 |    Matches any number of segments, the values being stored as an array
 |    in the "bar" parameter of the returned match object
 |
 Starts a segment, matching "/foo"

Anonymous Splat/Glob

"/foo/*"
 ^    ^
 |    Matches any number of segments, the values will not appear in the
 |    returned match object
 |
 Starts a segment, matching "/foo"

Optional Segments

"/foo(/baz)/baz"
 ^   ^    ^^
 |   |    |Starts a new segment, that matches "/baz"
 |   |    |
 |   |    Ends the optional segment
 |   |
 |   Starts an optional segment, this segment need not be in the path being
 |   matched for the match to be successful
 |
 Starts a segment, matching "/foo"

More examples

Examples of template usage cases you can find in our test files.

S3 event notification limitations

S3 event notifications are limited to filter file events only by predefined prefix and suffix. This could be problematic in situation where you decide to store output files in the same directory structure as the input image. This could cause S3 to fire new event notification for each output image saved in that path. In extreme case this could lead to situation where Lambda functions are executed in never ending loop. But, we are prepared to prevent such incidents, or maybe I should rather say, we are prepared to minimise the potential damage.

Each processed file is stored with additional Metadata: { img-processed: true }. Also, each input file that we process is checked against this flag, and if it's present, we will stop the processing flow with "Object was already processed." error message.