Upload images to Imgur from Mathematica - post

Question

Here's a challenge to all mathematica tag followers. Let's make it a lot more convenient to insert images into SO post from Mathematica by creating an imgur uploader.
How can we create a function imgur[g_] that will rasterize its argument (making sure that the final size is not wider than the width of StackOverflow posts), convert it to PNG, upload it to imgur, and return a ready to be pasted MarkDown line such as ![Mathematica graphic](http://i.imgur.com/ZENa4.jpg) ?
Useful references:
Imgur API
Example of using POST request from Mathematica on WRI blog (posting to Twitter) by ragfield
Example of using POST requests from Mathematica on SO (uploading to ifile.it)
I failed to adapt this latter method to uploading an image without exporting it to a file first.
Warning, use with care! StackOverflow uses a separate imgur installation that keep images indefinitely. If you use the main imgur, the images will disappear after 6 months if no one views them. Unfortunately as of 2011 November there seems to be no official way to upload images to StackOverflow programmatically.
Update: See below a solution for uploading to StackOverflow directly.

Answer 1

A little bird just informed me of a Mathematica solution to this question (the underlying implementation still uses JLink, but this answer hides all the java related code):
imgur[expr_] := Module[
{url, key, image, data, xml, imgurUrl},
url = "http://api.imgur.com/2/upload";
key = "c07bc3fb59ef878d5e23a0c4972fbb29";
image = Fold[ExportString, expr, {"PNG", "Base64"}];
xml = Import[url,
"XML", "RequestMethod" -> "POST",
"RequestParameters" -> {"key" -> key, "image" -> image}];
imgurUrl = Cases[xml, XMLElement["original", {}, {string_}] :> string,
Infinity][[1]];
"![Mathematica graphic](" <> imgurUrl <> ")"
]
This is V8 only and the XML import options "RequestMethod" and "RequestParameters" are undocumented and experimental (and therefore subject to change).

Answer 2

Note: Get an ready-made palette with this functionality here.
Arnoud's solution got me excited and impatient, so here's an improvement to it. I couldn't have done this without studying his code. This version seems to be somewhat more reliable and less prone to timeout errors, but to be honest, I know no Java at all, so any improvements are welcome.
Most importantly: this version uploads to stack.imgur.com directly, so it's safe to use here on StackOverflow, without having to worry that uploaded images will disappear after a while.
I provide three functions:
stackImage uploads the expression, exported as PNG, and returns the URL
stackMarkdown returns the markdown, ready to be copied
stackCopyMarkdown copies the markdown to the clipboard
Next step: create a palette button that does this automatically for the selected graphic in the notebook. Improvements to the code are very welcome.
Needs["JLink`"]
stackImage::httperr = "Server returned respose code: `1`";
stackImage::err = "Server returner error: `1`";
stackImage[g_] :=
Module[
{getVal, url, client, method, data, partSource, part, entity, code,
response, error, result},
(* this function attempts to parse the response fro the SO server *)
getVal[res_, key_String] :=
With[{k = "var " <> key <> " = "},
StringTrim[
First#StringCases[First#Select[res, StringMatchQ[#, k ~~ ___] &],
k ~~ v___ ~~ ";" :> v],
"'"]
];
data = ExportString[g, "PNG"];
JavaBlock[
url = "https://stackoverflow.com/upload/image";
client = JavaNew["org.apache.commons.httpclient.HttpClient"];
method = JavaNew["org.apache.commons.httpclient.methods.PostMethod", url];
partSource = JavaNew["org.apache.commons.httpclient.methods.multipart.ByteArrayPartSource", "mmagraphics.png", MakeJavaObject[data]#toCharArray[]];
part = JavaNew["org.apache.commons.httpclient.methods.multipart.FilePart", "name", partSource];
part#setContentType["image/png"];
entity = JavaNew["org.apache.commons.httpclient.methods.multipart.MultipartRequestEntity", {part}, method#getParams[]];
method#setRequestEntity[entity];
code = client#executeMethod[method];
response = method#getResponseBodyAsString[];
]
If[code =!= 200, Message[stackImage::httperr, code]; Return[$Failed]];
response = StringTrim /# StringSplit[response, "\n"];
error = getVal[response, "error"];
result = getVal[response, "result"];
If[StringMatchQ[result, "http*"],
result,
Message[stackImage::err, error]; $Failed]
]
stackMarkdown[g_] := "![Mathematica graphics](" <> stackImage[g] <> ")"
stackCopyMarkdown[g_] := Module[{nb, markdown},
markdown = Check[stackMarkdown[g], $Failed];
If[markdown =!= $Failed,
nb = NotebookCreate[Visible -> False];
NotebookWrite[nb, Cell[markdown, "Text"]];
SelectionMove[nb, All, Notebook];
FrontEndTokenExecute[nb, "Copy"];
NotebookClose[nb];
]
]
Update:
Here's a button that will show a preview of the selection and will offer uploading (or cancelling). It requires the previous functions to be defined.
Button["Upload to SO",
Module[{cell = NotebookRead#InputNotebook[], img},
If[cell =!= {}, img = Rasterize[cell];
MessageDialog[
Column[{"Upload image to StackExchange sites?",
img}], {"Upload and copy MarkDown" :> stackCopyMarkdown[img],
"Cancel" :> Null}, WindowTitle -> "Upload to StackExchange"]]]]
Unfortunately I can't put the button in a palette (CreatePalette) because the palette dimensions will influence the rasterization. Solutions to this problem are welcome.
Update 2:
Based on the answer to this question, here's a working Windows-only palette button:
button = Button["Upload to SO",
Module[{sel},
FrontEndExecute[
FrontEndToken[FrontEnd`SelectedNotebook[], "CopySpecial", "MGF"]];
sel = Cases[NotebookGet#ClipboardNotebook[],
RasterBox[data_, ___] :>
Image[data, "Byte", ColorSpace -> "RGB", Magnification -> 1],
Infinity];
If[sel =!= {},
With[{img = First[sel]},
MessageDialog[
Column[{"Upload image to StackExchange sites?",
img}], {"Upload and copy MarkDown" :> stackCopyMarkdown[img],
"Cancel" :> Null}, WindowTitle -> "Upload to StackExchange"]
]
]
]
]
CreatePalette[button]
Warning: it destroys the clipboard contents even if you click cancel in the preview box.

Answer 3

Note: This is using the anonymous imgur uploader with my anonymous key. The imgur site restricts uploads to 50 uploads/hour which should be fine normally, but this may cause a problem if a lot of people try this simultaneously. So please get your own anonymous key here:
http://imgur.com/register/api_anon
And then replace the key in the code below with your own key (thanks!).
The trickiest part to code was the conversion from a Mathematica expression to PNG image to Base64 encoding to URL encoding. There are about a 1,000 ways to do it wrong and I think I managed to try them all.
The code breaks down into a few pieces:
Construct the POST url
Make the HTTP connection
Send the POST url
Read back the result, which is XML
Extract the imgur url from the XML
Format the imgur url as markdown (or as a Mathematica Hyperlink function).
Here is the code:
imgur[expr_] :=
Module[{url, key, image, data, jUrl, jConn, jWriter, jInput, buffer,
byte, xml, imgurUrl},
Needs["JLink`"];
JLink`JavaBlock[
JLink`LoadJavaClass["java.net.URLEncoder"];
url = "http://api.imgur.com/2/upload";
key = "c07bc3fb59ef878d5e23a0c4972fbb29";
image = ExportString[ExportString[expr, "PNG"], "Base64"];
data =
URLEncoder`encode["key" , "UTF-8"] <> "=" <>
URLEncoder`encode[ key , "UTF-8"] <> "&" <>
URLEncoder`encode["image" , "UTF-8"] <> "=" <>
URLEncoder`encode[ image , "UTF-8"] ;
jUrl = JLink`JavaNew["java.net.URL", url];
jConn = jUrl#openConnection[];
jConn#setDoOutput[True];
jWriter =
JLink`JavaNew["java.io.OutputStreamWriter",
jConn#getOutputStream[]];
jWriter#write[data];
jWriter#flush[];
jInput = jConn#getInputStream[];
buffer = {};
While[(byte = jInput#read[]; byte >= 0), AppendTo[buffer, byte]];
];
xml = ImportString[FromCharacterCode[buffer], "XML"];
imgurUrl =
Cases[xml,
XMLElement["original", {}, {string_}] :>
string, \[Infinity]][[1]];
"![Mathematica graphic](" <> imgurUrl <> ")"
]
Testing:
In[]:= g = Graphics[{Blue, Disk[]}, PlotRange -> 1.2, ImageSize -> Small];
pic = Overlay[{Blur[Binarize#g, 10], g}];
imgur[pic]
Out[]= ![Mathematica graphic](http://i.imgur.com/eGOlL.png)
And the actual image: