Microsoft.AspNetCore.Mvc.Localization.LocalizedHtmlStringConvert PNG to Base64 in ASP

Convert PNG to Base64 in ASP

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Topic

Author : Shaggy
Subject : Convert PNG to Base64 in ASP
Posted : 10 October 2013, 08:05
Message :

Greetings, strangers

Hoping one of you may be able to help me with this little script.
I'm trying to write an ASP script to convert PNG files submitted through a form to Base64 strings without writing the file to the server first.
The HTML for the form is straightforward, as follows:

Code:

<form enctype="multipart/form-data" method="post">
	<input type="file" name="file" />
	<button type="submit">Convert</button>
</form>

And the code to process it and convert it to Base64 is as follows:

Code:

dim objXml,objStream,binFile
binFile=request.binaryread(request.totalbytes)
set objStream=server.createobject("ADODB.Stream")
objStream.type=1
objStream.open
objStream.write binFile
set objXML=server.createobject("MSXml2.DOMDocument")
set objXml=objXml.createelement("Base64Data")
objXml.datatype="bin.base64"
objXml.nodetypedvalue=objStream.read
response.write replace objXml.text
objStream.close:set objStream=nothing:set objXml=nothing

All works well, except the Base64 string includes the form "header" - Example:

Code:

------WebKitFormBoundarydXk7Jv8nzVuN2zps
Content-Disposition: form-data; name="file"; filename="file.png"
Content-Type: image/png

[File data here]

Any suggestions/pointers for stripping it out at any stage of the process before the encoding takes place? Ideally, I'd also like to read "filename" and "Content-Type" into variables to help me verify that the file is actually a PNG.

Replies ...

Reply Author: Carefree
Replied on: 10 October 2013, 10:17
Message:

You might try replacing your response.write with something like this:

Code:


If instr(objXml.text,"Content-Type: image/png") AND lCase(right(filename,4))=".png" then
	response.Write replace(instr(objXml.text,"Content-Type: image/png")+24)
End If

That SHOULD just start from the position after that line (23 characters of text plus a line feed/carriage return).

Reply Author: Shaggy
Replied on: 10 October 2013, 10:37
Message:

Thanks, Carefree, but objXml.text is Base64 encoded binary data so that's not going to work.

Reply Author: Carefree
Replied on: 10 October 2013, 11:04
Message:

So objStream is your initial file? OK.

Code:


If instr(objStream,"Content-Type: image/png") AND lCase(right(filename,4))=".png" then
	response.Write replace(instr(objXml.text,"Content-Type: image/png")+24)
End If

Reply Author: Shaggy
Replied on: 10 October 2013, 11:10
Message:

No, the initial data comes from binFile=request.binaryread(request.totalbytes) and I need to strip out the header data before binFile gets passed to the stream so that all that's going into the stream is the file data.

Reply Author: Carefree
Replied on: 15 October 2013, 15:47
Message:

Originally posted by Shaggy
No, the initial data comes from binFile=request.binaryread(request.totalbytes) and I need to strip out the header data before binFile gets passed to the stream so that all that's going into the stream is the file data.

Code:


If instr(binfile,"Content-Type: image/png") AND lCase(right(filename,4))=".png" then
	For i = 1 to len(binfile)
		If mid(binfile,i,23)="Content-Type: image/png" Then
			binfile=mid(binfile,i+24,len(binfile)-i+24)
			Exit For
		End If
	Next
End If