datauris

Data URI Helpers

datauris - helpers to parse (decode) and build (encode) data uris incl. (strict) base64-encoded/decoded images and more

• home :: github.com/0xCompute/ethscribe
• bugs :: github.com/0xCompute/ethscribe/issues
• gem :: rubygems.org/gems/datauris
• rdoc :: rubydoc.info/gems/datauris

What are Data URIs?!

Data URI Syntax via Wikipedia:

The syntax of data URIs is defined in Request for Comments (RFC) 2397, published in August 1998, and follows the URI scheme syntax. A data URI consists of:

data:[<mediatype>][;base64],<data>

• The scheme, data. It is followed by a colon (:).
• An optional media type. The media type part may include one or more parameters, in the format attribute=value, separated by semicolons (;). A common media type parameter is charset, specifying the character set of the media type, where the value is from the IANA list of character set names. If one is not specified, the media type of the data URI is assumed to be text/plain;charset=US-ASCII.
• An optional base64 extension base64, separated from the preceding part by a semicolon. When present, this indicates that the data content of the URI is binary data, encoded in ASCII format using the Base64 scheme for binary-to-text encoding. The base64 extension is distinguished from any media type parameters by virtue of not having a =value component and by coming after any media type parameters.
• The data, separated from the preceding part by a comma (,). The data is a sequence of zero or more octets represented as characters. The comma is required in a data URI, even when the data part has zero length. The characters permitted within the data part include ASCII upper and lowercase letters, digits, and many ASCII punctuation and special characters. Note that this may include characters, such as colon, semicolon, and comma which are delimiters in the URI components preceding the data part. Other octets must be percent-encoded. If the data is Base64-encoded, then the data part may contain only valid Base64 characters. Note that Base64-encoded data: URIs use the standard Base64 character set (with + and / as characters 62 and 63) rather than the so-called "URL-safe Base64" character set.

Usage

Parse • Build

Parse

Let's try and parse the Wikipedia Data URI examples:

uri = "data:text/vnd-example+xyz;foo=bar;base64,R0lGODdh"
DataUri.valid?( uri )  
#=> true
data, mediatype = DataUri.parse( uri )    ## returns 1) data, 2) mediatype (+parameters)
#=> "<blob>", "text/vnd-example+xyz;foo=bar"

uri = "data:text/plain;charset=UTF-8;page=21,the%20data:1234,5678"
DataUri.valid?( uri )  
#=> true
data, mediatype = DataUri.parse( uri )    ## returns 1) data, 2) mediatype (+parameters)
#=> "the data:1234,5678", "text/plain;charset=UTF-8;page=21"


uri = "data:image/jpeg;base64,/9j/4AAQSkZJRgABAgAAZABkAAD/"
DataUri.valid?( uri )  
#=> true
data, mediatype = DataUri.parse( uri )    ## returns 1) data, 2) mediatype (+parameters)
#=> "<blob>", "image/jpeg"

Let's try the DataUri helpers on inscriptions (that encode the "on-chain" data in Data URIs). A valid inscribe must use a valid data uri in the calldata.

The "useless" (null) minimum - no media-type, and zero-length data - is:

uri = "data:,"

DataUri.valid?( uri )  
#=> true
data, mediatype = DataUri.parse( uri )    ## returns 1) data, 2) mediatype (+parameters)
#=> "", ""

Let's try the (genesis) inscribe no. 0:

uri = "data:image/jpeg;base64,/9j/4AAQSkZJRgABAgAAZABkAAD/7AARRHV..."

DataUri.valid?( uri )  
#=> true
data, mediatype = DataUri.parse( uri )    ## returns 1) data, 2) mediatype (+parameters)
#=> "<blob>", "image/jpeg"

## let's save the jpeg image (blob)
write_blob( "0.jpeg", data )

and voila!

Let's try the inscribe no. 15:

uri = "data:image/png;base64,/9j/4gxYSUNDX1BST0ZJTEUAAQEAAAxITGlubwIQAAB..."

DataUri.valid?( uri )  
#=> true
data, mediatype = DataUri.parse( uri )    ## returns 1) data, 2) mediatype (+parameters)
#=> "<blob>", "image/png"

## let's save the png image (blob)
write_blob( "15.png", data )

and voila!

Build

Let's build Data URIs.

uri = DataUri.build( "" )
#=> "data:,"

uri = DataUri.build( "the data:1234,5678", "text/plain" )
#=> "data:text/plain,the%20data:1234,5678"

# let's try images
data = read_blob( "0.jpeg" )
uri = DataUri.build( data, "image/jpeg" )
#=> "data:image/jpeg;base64,/9j/4AAQSkZJRgABAgAAZABkAAD/7AARRHV..."

data = read_blob( "15.png" )
uri = DataUri.build( data, "image/png" )
#=> "data:image/png;base64,/9j/4gxYSUNDX1BST0ZJTEUAAQEAAAxITGlubwIQAAB..."

That's it for now.

Bonus - More Blockchain (Crypto) Tools, Libraries & Scripts In Ruby

See /blockchain at the ruby code commons (rubycocos) org.

Questions? Comments?

Join us in the 0xCompute discord (chat server) (or in the more general Ethscription discord). Yes you can. Your questions and commentary welcome.

Or post them over at the Help & Support page. Thanks.