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manufacturing flic.kr style photo URLs

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kellan is a group administrator kellan says:

Super quick note, hopefully sufficient info.

The format for the short photo URLs is

flic.kr/p/{short-photo-id}

A short photo id is a base58 conversion of the photo id. Base58 is like base62 [0-9a-zA-Z] with some characters removed to make it less confusing when printed. (namely 0, O, I, and l).

So that leaves an alphabet of: 123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ

I'm including below a variation of the code we use to do base conversion. Note it doesn't use modulus because PHP's modulus operator overflows for large numbers (like photo ids)


function base_encode($num, $alphabet) {
$base_count = strlen($alphabet);
$encoded = '';
while ($num >= $base_count) {
$div = $num/$base_count;
$mod = ($num-($base_count*intval($div)));
$encoded = $alphabet[$mod] . $encoded;
$num = intval($div);
}

if ($num) $encoded = $alphabet[$num] . $encoded;

return $encoded;
}

function base_decode($num, $alphabet) {
$decoded = 0;
$multi = 1;
while (strlen($num) > 0) {
$digit = $num[strlen($num)-1];
$decoded += $multi * strpos($alphabet, $digit);
$multi = $multi * strlen($alphabet);
$num = substr($num, 0, -1);
}

return $decoded;
}

Originally posted at 9:42AM, 13 April 2009 PDT (permalink)
kellan edited this topic 61 months ago.

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blech​ says:

Thank you. I was trying to reverse engineer the base58 string, and getting close, but no cigar. (If the photo ID space wasn't quite so sparsely populated where I was sampling it, I might have managed, too.)
61 months ago (permalink)

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alto maltés says:

Cool.
61 months ago (permalink)

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matt says:

Someone jam this in a twitter client, pronto!
61 months ago (permalink)

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Eli the Bearded says:

BC math is available in PHP.

bcmod -- Get modulus of an arbitrary precision number
61 months ago (permalink)

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Richard Cunningham says:

It would be good if this was translatable to a photo url with out any requests (in the way twitpic, twitgoo, yfrog etc. do).

Just knowing the photo id doesn't get you to photo url since you need the secret, farm and server (https://www.flickr.com/services/api/misc.urls.html). We would have to do a flickr.photos.getInfo for each photo.

unless I'm missing something?
61 months ago (permalink)

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fraserspeirs says:

Here's an implementation of the encoding part in Objective-C: gist.github.com/101674
61 months ago (permalink)

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Jiayong Ou says:

And here's an implementation in Ruby:

gist.github.com/101753
61 months ago (permalink)

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faygate says:

C# example:

http://www.faygate.net/post/133462295/tinyurlcode
58 months ago (permalink)

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Xenocryst @ Antares Scorpii says:

An example for a bookmarklet:

javascript:void(prompt('Flic.kr short ID (base58)',(function(num){if(typeof num!=='number')num=parseInt(num);var enc='', alpha='123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'; var div=num,mod;while(num>=58){div=num/58;mod=num-(58*Math.floor(div));enc=''+alpha.substr(mod,1) +enc;num=Math.floor(div);} return(div)?''+alpha.substr(div,1)+enc:enc;})(prompt('Flickr picture ID'))))


ETA: A more useful variant, giving you the respective Flic.kr-URL, if activated on a photo display page, might be:

javascript:void((function(){var m=window.location.href.match(/^https?:\/\/[^/]*\bflickr\.com\/(photos\/[^/]+\/(\d+))/i);if(m.length&&m[2]) prompt('Short Flic.kr-URL for\n"'+m[1]+'":','http://flic.kr/p/'+(function(num)
{if(typeof num!=='number')num=parseInt(num);var enc='';var alpha='123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';var div=num; while(num>=58){div=num/58;var mod=(num-(58*Math.floor(div)));enc=''+alpha.substr(mod,1)+enc;n um=Math.floor(div);}
return(div)?''+alpha.substr(div,1)+enc:enc;})(m[2]));})())

Originally posted 58 months ago. (permalink)
dopiaza (a group admin) edited this topic 45 months ago.

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stevefaeembra says:

quick python snippet for encoding...

num=12345678
a='123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'
bc=len(a)
enc=''
while num>=bc:
    div,mod=divmod(num,bc)
    enc = a[mod]+enc
    num = int(div)
enc = a[num]+enc
print "flic.kr/p/%s" % (enc,)
Originally posted 58 months ago. (permalink)
stevefaeembra edited this topic 58 months ago.

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taiyofj says:

javascript decoder.

function base58_decode( snipcode )
{
    var alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ' ;
    var num = snipcode.length ;
    var decoded = 0 ;
    var multi = 1 ;
    for ( var i = (num-1) ; i >= 0 ; i-- )
    {
        decoded = decoded + multi * alphabet.indexOf( snipcode[i] ) ;
        multi = multi * alphabet.length ;
    }
    return decoded;
}

I'm using above base 58 decode function on pbtweet
Originally posted 58 months ago. (permalink)
taiyofj edited this topic 58 months ago.

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Wonderm00n says:

Great topic kellan!

I've just used your base_encode function on flicktotwitt.com

THANKS!
58 months ago (permalink)

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Tim Parenti says:

Thanks for the information. I've created a simple, web-based implementation at http://www.timparenti.com/dev/flickr/shortlink/

It's meant for the people who don't necessarily want or need Twitter integration, but just want to convert URLs (although I might add Twitter integration later).

It can handle conversions from a short URL to a photo ID and vice-versa. I'm planning to add full URL support so you can just paste a long URL from your browser bar and it will extract the relevant bit (the photo ID).

If anyone has any ideas to improve it, please let me know. Here's hoping someone at least finds it useful.
Originally posted 58 months ago. (permalink)
Tim Parenti edited this topic 58 months ago.

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burntoutcar says:

Any reason why this can't be incorporated into the "Share This" widget at the top right of each photo page?
58 months ago (permalink)

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kellan is a group administrator kellan says:

Btw valid paths after the photo id will be passed along now.

So flic.kr/p/$photoid/sizes/l works as do flic.kr/p/$photoid/nearby and flic.kr/p/$photoid/favorites
58 months ago (permalink)

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Kohichi says:

python decoder snippet
This code based on taiyofj's javascript one,


def b58decode(s):
    alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'
    num = len(s)
    decoded = 0 ;
    multi = 1;
    for i in reversed(range(0, num)):
        decoded = decoded + multi * ( alphabet.index( s[i] ) )
        multi = multi * len(alphabet)
    return decoded;

58 months ago (permalink)

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Rex Roof says:

If these are really Base58, why doesn't the Math:Int2Base perl module work?
57 months ago (permalink)

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Rex Roof says:

Oooh, because you aren't using regular Base58. you're using Base62 with your own characters removed. Sorry, answered my own question.
57 months ago (permalink)

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(robcee) says:

my colleague Johnath converted this to a shorter Firefox bookmarklet using the page's contained <link rev="canonical"> tag:

javascript:var%20l=document.querySelectorAll("link");for(i=l.length-1;i>=0;--i){if(/flic\.kr/.test(l.item(i).href))prompt("Have%20a%20url!",l.item(i).href);}
Originally posted 57 months ago. (permalink)
(robcee) edited this topic 57 months ago.

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cmort says:

and a simple variation of @robceemoz's post to send it straight to twitter

javascript:var%20l=document.querySelectorAll("link"); for(i=l.length-1;i>=0;--i){if(/flic\.kr/.test(l.item(i).href)) document.location='http://twitter.com/?status=Just%20posted:%20'+l.item(i).href;}
Originally posted 57 months ago. (permalink)
dopiaza (a group admin) edited this topic 41 months ago.

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bitrot says:

I've just posted up a Greasemonkey script based on Xenocryst @ Antares Scorpii's bookmarklet (above):

flic.kr Short URL Link
at userscripts.org

It looks like this:

flic.kr short URL screenshot

Hope you find it useful!
Originally posted 57 months ago. (permalink)
bitrot edited this topic 57 months ago.

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kellan is a group administrator kellan says:

Rex, don't know if you're still looking for a Perl module, but check out
search.cpan.org/~miyagawa/Encode-Base58-0.01/lib/Encode/B...
57 months ago (permalink)

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andrhamm says:

Will there ever be the ability to use this URL shortening for sets?
Originally posted 54 months ago. (permalink)
andrhamm edited this topic 54 months ago.

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opello says:

:
I revised your initial check against m as such:


if(m&&m.length&&m[2])

So that it doesn't introduce a javascript error when used on non-flickr pages (accidental clicks). I didn't see adding further error checking as worthwhile, but someone else might.
54 months ago (permalink)

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Zoolcar9 says:

I wrote a Firefox extension to get flic.kr shortened URL from context menu if you right click on Flickr photo, link, or Flickr photo page. Please try it
zoolcar9.lhukie.net/extensions/flic.kr.xpi

Please report any issues or suggestions at
www.flickr.com/photos/zoolcar9/sets/72157622750210617/com...
or at Flickr Hacks group
www.flickr.com/groups/flickrhacks/discuss/72157622750913301/
 
Originally posted 54 months ago. (permalink)
Zoolcar9 edited this topic 54 months ago.

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frog23-net says:

Here is the Java Version:
dl.dropbox.com/u/1844215/FlickrBaseEncoder.java
53 months ago (permalink)

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Richard Barnett says:

Any chance of m.flic.kr redirecting to an m.flickr.com page?
53 months ago (permalink)

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flowolf says:

i wrote a bash version to convert a photo ID into the base58 photo id and vice versa:
klienux.org/scripts/base58.sh.txt

have fun
52 months ago (permalink)

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kellan is a group administrator kellan says:

And I've added the much requested img urls.

flic.kr/p/7sqMtA
flic.kr/p/img/7sqMtA.jpg
flic.kr/p/img/7sqMtA_s.jpg
flic.kr/p/img/7sqMtA_t.jpg
flic.kr/p/img/7sqMtA_m.jpg

Generalized form:

flic.kr/p/img/$shortid_[stm].jpg

Fun fact: this was built for del.icio.us many years ago, I just added support for the short url identifiers.

Happy New Year
52 months ago (permalink)

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Jan Hapke says:

It would be cool if this also worked for sets. So we could use URLs like

flic.kr/s/aHsj9AnSbu

Or generally more functions of flickr, like maybe slide shows, collections, you name it.

The problem is that set ids are very long (for some reason longer than photo ids) so the resulting short URLs might still be too long for twitter.
52 months ago (permalink)

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PetroleumJelliffe says:

Does the URL shortener only work for photos because you can still access photos with just their ID using this:

www.flickr.com/photo.gne?id=2293005459

There isn't an equivalent for sets that I know of. That is, you need to know who created a set to access one, but for photos you don't.
51 months ago (permalink)

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Sybren A. Stüvel says:

Support for the short photo page URL has been included in version 1.4 of the Python FlickrAPI kit, released today. For more information see stuvel.eu/archive/119/python-flickr-api-14-released
51 months ago (permalink)

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jolinwarren says:

Here's an AppleScript version of the encoder in this post:


on base_encode(alphabet, num)
set base_count to count of alphabet
set encoded to ""
repeat while (num ≥ base_count)
set encoded to (item ((num mod base_count as integer) + 1) of alphabet) & encoded
set num to num div base_count
end repeat

if (num > 0) then set encoded to (item (num + 1) of alphabet) & encoded

return encoded
end base_encode

49 months ago (permalink)

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tjieftjaf says:

I use this function in MySQL:


DELIMITER $$

DROP FUNCTION IF EXISTS `BASE58` $$
CREATE FUNCTION `BASE58`( num BIGINT) RETURNS varchar(255)
DETERMINISTIC
BEGIN
DECLARE chars CHAR(58) DEFAULT "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";
DECLARE stream CHAR(32) DEFAULT "";
DECLARE res INT;
WHILE num > 0 DO
SET res = num % 58;
SET num = num DIV 58;
SET stream = CONCAT(MID( chars, res + 1, 1 ), stream);
END WHILE;
RETURN stream;

END $$

DELIMITER ;


And then in your SELECT, INSERT, etc.:

SELECT Title, CONCAT('http://flic.kr/p/', BASE58(Id)) FROM `Photo`;


Based on a post by Barry Gould on the MySQL forum.
46 months ago (permalink)

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whatsthatpicture says:

Hi, I'm not after Flickr's trade secrets, but is there any broad evidence as to how successful the implementation of short urls has been on Flickr, and how much they are used? I'm trying to get a feel for whether this is worth doing on a museums collection catalogue.
Originally posted 45 months ago. (permalink)
whatsthatpicture edited this topic 45 months ago.

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dopiaza is a group administrator dopiaza says:

I think it depends on how you expect your catalogue to get used. I see the short URLs bandied around a lot on Twitter, where space is at a premium, but I don't really see them much in other contexts.

When sharing URLs, I tend to prefer the long versions - you get more immediate contextual information that way.
45 months ago (permalink)

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scoopedup20 says:

where is the callback url field
41 months ago (permalink)

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andre.laszlo says:

It should be noted that if you try kellan's php algorithm above and get your id from the rest api interface for example, you get utf-8 encoded data and the algorithm will not work unless you convert it to something that php can handle. Using iconv() for example. This is what happens when you end up with 4gLq58 all the time :)
39 months ago (permalink)

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alavoy says:

I posted an update to the Base 58 Objective-C Encoder to now include Decoding:

gist.github.com/819739
39 months ago (permalink)

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Milgrim says:

more python code:


alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'
base = len(alphabet)

def b58encode(div, s=''):
    if div >= base:
        div, mod = divmod(div, base)
        return b58encode(div, alphabet[mod] + s)
    return alphabet[div] + s

def b58decode(s):
    return sum(alphabet.index(c) * pow(base, i) for i, c in enumerate(reversed(s)))

38 months ago (permalink)

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tjieftjaf says:

It looks like flic.kr/s/{short-set-id} is now working too!
35 months ago (permalink)

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daruyanagi says:

by C# (string class extention)

const string BASE58 = "123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ";

public static long Base58Decode(this string input)
{
return BaseDecode(input, BASE58);
}

public static long BaseDecode(string input, string alphabet)
{
long decoded = 0, multi = 1;

foreach (var c in input.Reverse())
{
decoded += multi * alphabet.IndexOf(c);
multi *= alphabet.Length;
}

return decoded;
}

blog.daruyanagi.net/archives/264

I made NuGet package to embed a photo on Flickr to your homepage. Please enjoy !

Flickr2Html nuget.org/List/Packages/Flickr2Html

@Flickr2Html.GetHtml5("http://flic.kr/p/asHoxQ")
31 months ago (permalink)

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tarmo888 says:

Would be nice if these 2 formats would be added to shorturl too.
www.flickr.com/groups/api/discuss/72157629196782290/
25 months ago (permalink)

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richard.mark.ward says:

Sorry for dredging up a very old discussion - but how are the set ids encoded? using the base58 encoder / decoder for the short url / id seems not to match.
9 months ago (permalink)

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dmitriyk says:

Not that there's clamor for this, but here's a Scala Base58 encoder and decoder:

gist.github.com/thedmitriyk/6009335

It's not letting me paste this inline for whatever reason, so grab the Gist.
Originally posted 9 months ago. (permalink)
dmitriyk edited this topic 9 months ago.

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dmitriyk says:

In writing some unit tests for my application, I came across a curious and nonobvious property of Flickr's Base58 algorithm implementation that I feel should be documented somewhere.

For any given input to the encode() function, the range of the function does not include strings starting with the letter "1" Therefore, the domain of the decode() function similarly does not include strings starting with the letter "1" What actually happens is that decode(x) == decode("1" + x); that is to say, the space of unencoded IDs is not isomorphic to the space of encoded IDs.

If you pass a string starting with the letter "1" to decode, you're going to have a bad time. I've updated my own implementation of the algorithm to reflect that.
7 months ago (permalink)

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