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  ?
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.
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).
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 URLstackMarkdown returns the markdown, ready to be copiedstackCopyMarkdown 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.
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[]= 
And the actual image:
{var%20f='http://v.t.sina.com.cn/share/share.php?appkey=1515056452',u=z||d.location,p=['&url=',e(u),'&title=',e(t||d.title),'&source=',e(r),'&sourceUrl=',e(l),'&content=',c||'gb2312','&pic=',e(p||'')].join('');function%20a(){if(!window.open([f,p].join(''),'mb',['toolbar=0,status=0,resizable=1,width=440,height=430,left=',(s.width-440)/2,',top=',(s.height-430)/2].join('')))u.href=[f,p].join('');};if(/Firefox/.test(navigator.userAgent))setTimeout(a,0);else%20a();})(screen,document,encodeURIComponent,'','','https://i.imgur.com/eGOlL.png', '推荐 贪生不怕死 的文章《Upload images to Imgur from Mathematica》','https://www.manongdao.com/article-197928.html','页面编码gb2312|utf-8默认gb2312'));){kind=link}