JSON Schema : How to specify that a string property contains base64-encoded PNG images

By adding : The contentMediaType and contentEncoding



Example

Here is an example schema, illustrating the use of "contentEncoding" and "contentMediaType":

{
    "type": "string",
    "contentEncoding": "base64",
    "contentMediaType": "image/png"
}

                    

Instances described by this schema should be strings, and their values should be interpretable as base64-encoded PNG images.

Another example:

{
    "type": "string",
    "contentMediaType": "text/html"
}

                    

Instances described by this schema should be strings containing HTML, using whatever character set the JSON string was decoded into (default is Unicode)

 contentEncoding

If the instance value is a string, this property defines that the string SHOULD be interpreted as binary data and decoded using the encoding named by this property. RFC 2045, Sec 6.1 [RFC2045]lists the possible values for this property.

The value of this property MUST be a string.

contentMediaType

The value of this property must be a media type, as defined by RFC 2046 [RFC2046]. This property defines the media type of instances which this schema defines.

The value of this property MUST be a string.

The value of this property SHOULD be ignored if the instance described is not a string.

If the "contentEncoding" property is not present, but the instance value is a string, then the value of this property SHOULD specify a text document type, and the character set SHOULD be the character set into which the JSON string value was decoded (for which the default is Unicode).

More informations : https://stackoverflow.com/questions/51675207/json-schema-is-it-possible-to-validate-a-string-is-a-json-array-or-object/51699771#51699771