I've got a small sockets application where I communicate with a web server
via async sockets method.
Using the ASCIIEncoding Class, I convert strings to byte arrays (and vice
versa) in conjunction with beginSend and beginReceive (and their
corresponding callbacks). So long as the web server and I just deal in
text, life is easy.
Now there's an image I want to request and then display in my app, it's a
dynamic PNG image that's generated by some .aspx page on the web server. So
my GET, to request this image, looks like this:
GET /MakeThePNG.aspx HTTP/1.1
Host: www.url.com
And here's the website's response:
HTTP/1.1 200 OK
Date: Thu, 01 Dec 2005 20:28:01 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 1.1.4322
Transfer-Encoding: chunked
Cache-Control: private, max-age=1800
Content-Type: image/png
39c9
?PNG
<a bunch of data>
0
I need to turn this response (sans the header, I'm assuming, but I'm unsure
which portions of the body) into an image object that I can display in a
picture box & save to disk. I've tried messing around with a Memory Stream,
and with that, tried including the whole body portion, just the <a bunch of
data> portion, but my attempts thus far are ultimately met with an Invalid
Argument exception when I try to make a new Image.FromStrea m with my Memory
Stream. I've tried to save said portions of the buffer to disk, but it does
not make a valid png file. So I'm not carving the data out of the body
correctly, or, it's not encoded correctly, or... ? I'm stumped. 2  2086 
Ok, the answer was to read up on how PNGs are put together. http://www.w3.org/TR/PNG/
PNGs start with with 8 "signature" bytes, 137 80 78 71 13 10 26 10. Those
are the first 8 bytes of the PNG file.
PNGs end with an "IEND" chunk, literally "IEND" (73 69 78 68), followed by 4
more bytes (CRC portion of the chunk). Those are the last 8 bytes of the
PNG file.
As soon as I exctracted the bytes from the Signature to the IEND chunk
(inclusive) and fed it to a memory stream, thus correctly carving out the
whole PNG file and nothing but the PNG file, Image.FromStrea m magically
turned the memory stream into an image.
"1388-2/HB" <1@1.net> wrote in message
news:43******** **************@ news.usenetmons ter.com... I've got a small sockets application where I communicate with a web server
via async sockets method.
Using the ASCIIEncoding Class, I convert strings to byte arrays (and vice
versa) in conjunction with beginSend and beginReceive (and their
corresponding callbacks). So long as the web server and I just deal in
text, life is easy.
Now there's an image I want to request and then display in my app, it's a
dynamic PNG image that's generated by some .aspx page on the web server.
So my GET, to request this image, looks like this:
GET /MakeThePNG.aspx HTTP/1.1
Host: www.url.com
And here's the website's response:
HTTP/1.1 200 OK
Date: Thu, 01 Dec 2005 20:28:01 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 1.1.4322
Transfer-Encoding: chunked
Cache-Control: private, max-age=1800
Content-Type: image/png
39c9
?PNG
<a bunch of data>
0
I need to turn this response (sans the header, I'm assuming, but I'm
unsure which portions of the body) into an image object that I can display
in a picture box & save to disk. I've tried messing around with a Memory
Stream, and with that, tried including the whole body portion, just the <a
bunch of data> portion, but my attempts thus far are ultimately met with
an Invalid Argument exception when I try to make a new Image.FromStrea m
with my Memory Stream. I've tried to save said portions of the buffer to
disk, but it does not make a valid png file. So I'm not carving the data
out of the body correctly, or, it's not encoded correctly, or... ? I'm
stumped.
why dont you just use a HTTP stream and read it as binary?! its so much
easier
"1388-2/HB" <1@1.net> wrote in message
news:43******** **************@ news.usenetmons ter.com... Ok, the answer was to read up on how PNGs are put together.
http://www.w3.org/TR/PNG/
PNGs start with with 8 "signature" bytes, 137 80 78 71 13 10 26 10. Those
are the first 8 bytes of the PNG file.
PNGs end with an "IEND" chunk, literally "IEND" (73 69 78 68), followed by
4 more bytes (CRC portion of the chunk). Those are the last 8 bytes of
the PNG file.
As soon as I exctracted the bytes from the Signature to the IEND chunk
(inclusive) and fed it to a memory stream, thus correctly carving out the
whole PNG file and nothing but the PNG file, Image.FromStrea m magically
turned the memory stream into an image.
"1388-2/HB" <1@1.net> wrote in message
news:43******** **************@ news.usenetmons ter.com... I've got a small sockets application where I communicate with a web
server via async sockets method.
Using the ASCIIEncoding Class, I convert strings to byte arrays (and vice
versa) in conjunction with beginSend and beginReceive (and their
corresponding callbacks). So long as the web server and I just deal in
text, life is easy.
Now there's an image I want to request and then display in my app, it's a
dynamic PNG image that's generated by some .aspx page on the web server.
So my GET, to request this image, looks like this:
GET /MakeThePNG.aspx HTTP/1.1
Host: www.url.com
And here's the website's response:
HTTP/1.1 200 OK
Date: Thu, 01 Dec 2005 20:28:01 GMT
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
X-AspNet-Version: 1.1.4322
Transfer-Encoding: chunked
Cache-Control: private, max-age=1800
Content-Type: image/png
39c9
?PNG
<a bunch of data>
0
I need to turn this response (sans the header, I'm assuming, but I'm
unsure which portions of the body) into an image object that I can
display in a picture box & save to disk. I've tried messing around with
a Memory Stream, and with that, tried including the whole body portion,
just the <a bunch of data> portion, but my attempts thus far are
ultimately met with an Invalid Argument exception when I try to make a
new Image.FromStrea m with my Memory Stream. I've tried to save said
portions of the buffer to disk, but it does not make a valid png file.
So I'm not carving the data out of the body correctly, or, it's not
encoded correctly, or... ? I'm stumped.
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