Webthumb Bluga.net is a great reliable online thumbnail webservice (I tried some others and find they were frequently disconnected). I have used this service to create these thumbnails on the Companies Page. They above all offer a free web service up to 100 request per month for any registered user. They have a REST API specification named easythumb I reproduced below for convenience:

Specification

• Endpoint: http://webthumb.bluga.net/easythumb.php
• Parameters:
  • user: Your Webthumb user_id available on your user page
  • url: Site to thumbnail, make sure to urlencode this
  • size: Size of the thumbnail to return small, medium1, medium2, large
  • cache: The # of days old a cached version of the thumbnail can be - 1 to 30
  • hash: The security hash components are covered below

Security Hash

The security hash is an md5 hash encoded in hexidecimal containing the following concatenated together

• current date: The current date in GMT/UTC formated as YYYYmmdd (in PHP this is the gmdate function)
• url: The url to thumbnail not urlencoded
• apikey: Your Bluga.net apikey

Example

Any example request looks like:
http://webthumb.bluga.net/easythumb.php?user=1&url=webthumb.bluga.net%2Fhome&hash=80a171c61c04084ba55cade47ce8d303&size=medium&cache=1

Let’s translate the spec into Rebol. The spec is saying the REST url is the concatenation of Endpoint, User, Url in encoded form and a hash code (will see just after) that is:

do http://reboltutorial.com/source/encode-url.r
REST-url: rejoin [Endpoint "?" "user=" user "&" url "=" (encode-url url) "&" "hash=" hash]

where (if we continue to just follow the spec):

gmt: now - now/zone
hash: checksum/method rejoin [gmt/year pad-zero gmt/month pad-zero gmt/day url apikey] 'MD5

Amazingly Rebol can easily generate the GMT components as well as do MD5 encryption with its checksum/method !

pad-zero is just a helper function:

pad-zero: func [ num ] [ either = 1 length? to-string num [ join "0" num ] [ num ] ]

Let’s test; first copy and paste the code below (you must register for free to get your user id and apikey number):

ask-parameters: [
  user: ask "User: "
  apikey: ask "ApiKey: "
  url: ask "Website Url (without http): "
]

do ask-parameters

To get your key registration login and copy these values:

Then paste the next instructions:

Endpoint: http://webthumb.bluga.net/easythumb.php
thumb-size: pick ["small" "medium" "medium1" "medium2" "large"] 4

pad-zero: func [ num ] [ either = 1 length? to-string num [ join "0" num ] [ num ] ]
gmt: now - now/zone
string-to-hash: rejoin [gmt/year pad-zero gmt/month pad-zero gmt/day url apikey]
hash: checksum/method string-to-hash 'MD5

do http://reboltutorial.com/source/encode-url.r
REST-url: to-url rejoin [Endpoint "?&size=" thumb-size "&" "user=" user "&" "url=" (encode-url url) "&" "hash=" hash]
write clipboard:// REST-url

;launch your default browser
Browse REST-url

Something wrong with the hash code maybe ?

First the type is not a string so we have to fix it with

hash-string: pick parse/all mold hash {#{}} 3

do http://reboltutorial.com/source/encode-url.r
REST-url: to-url rejoin [Endpoint "?&size=" thumb-size "&" "user=" user "&" "url=" (encode-url url) "&" "hash=" hash-string]

If you test again, it still doesn’t work. So let’s go to this online MD5 site and paste the content of string-to-hash by typing in rebol console:

;debug string-to-hash
write clipboard:// string-to-hash

The diffence is just Upper/Lowercase so to fix it, we just need to add

hash-string: lowercase hash-string

Here’s the final code:

;============================

ask-parameters: [
  user: ask "User: "
  apikey: ask "ApiKey: "
  url: ask "Website Url (without http): "
]

do ask-parameters

;=== Copy above first to clipboard if testing ===

Endpoint: http://webthumb.bluga.net/easythumb.php
thumb-size: pick ["small" "medium" "medium1" "medium2" "large"] 4

pad-zero: func [ num ] [ either = 1 length? to-string num [ join "0" num ] [ num ] ]
gmt: now - now/zone
string-to-hash: rejoin [gmt/year pad-zero gmt/month pad-zero gmt/day url apikey]
hash: checksum/method string-to-hash 'MD5
hash-string: pick parse/all mold hash {#{}} 3
hash-string: lowercase hash-string

do http://reboltutorial.com/source/encode-url.r
REST-url: to-url rejoin [Endpoint "?&size=" thumb-size "&" "user=" user "&" "url=" (encode-url url) "&" "hash=" hash-string]
write clipboard:// REST-url

;if you want to save in a directory:
;write/binary to-rebol-file ["c:thumbnails" ask "file name: "] read/binary REST-url

window: [image load REST-url]
view/title layout window "Thumbnail REST Web Service Client"

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