content type headers

[Dermot Paikkos]

Hi, 

I've got some old code to deal with and I have hit a problem. 

If there is a request for a page that has mixed content EG: 'text/html' 
and 'image/jpeg', the image media is not being displayed correctly under 
the FireFox browser. 

The way things currently work is that media other than text/html is 
output from a separate page, so you might have a bit of html that for an 
image that looks like this:



Within showImage.html you have a 1) a piece of code that supposedly sets 
the content_type to image/jpeg, and 2) calls to a function that 
literally prints the image based on is CGI param 'imageid'.

In my experiments, IE is correctly identifying the media and Firefox is 
not. However I think FF is expecting the content_type to be sent with 
the media and IE is guess* based upon the media it receives.

So my question, initially, is can a request set the content_type more 
than once?

Thanx,
Dp.



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Re: content type headers

[Gunnar Hjalmarsson]

Dermot Paikkos wrote:
If there is a request for a page that has mixed content EG: 'text/html' 
and 'image/jpeg', the image media is not being displayed correctly under 
the FireFox browser.


What exactly do you mean by that? When you use a browser to request a 
usual HTML page with IMG elements, there are multiple subsequent 
request/response pairs, one for each image. Could you post the source 
code of a page that behaves as you say?


The way things currently work is that media other than text/html is 
output from a separate page, so you might have a bit of html that for an 
image that looks like this:




Within showImage.html you have a 1) a piece of code that supposedly sets 
the content_type to image/jpeg, and 2) calls to a function that 
literally prints the image based on is CGI param 'imageid'.


As long as the images are accessible from the web, I do not see why you 
would need to use a separate script like that.


In my experiments, IE is correctly identifying the media and Firefox is 
not. However I think FF is expecting the content_type to be sent with 
the media and IE is guess* based upon the media it receives.


What if you simply try to view an image with FF directly?

http://www.example.com/images/someimage.jpg

If that's not displayed as expected, there may be something with the 
configuration of your FF browser.


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Gunnar Hjalmarsson
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RE: content type headers

[Hellman, Matthew]

>>Hi,
>>
>>I've got some old code to deal with and I have hit a problem.
>>
>>If there is a request for a page that has mixed content EG: 'text/html'
>>and 'image/jpeg', the image media is not being displayed correctly under
>>the FireFox browser.
>>
>>The way things currently work is that media other than text/html is
>>output from a separate page, so you might have a bit of html that for an
>>image that looks like this:
>>
>>
>>
>>Within showImage.html you have a 1) a piece of code that supposedly sets
>>the content_type to image/jpeg, and 2) calls to a function that
>>literally prints the image based on is CGI param 'imageid'.

This sounds fine, but it obviously isn't working right?  For some examples, 
see: http://www.perlmonks.org/?node_id=18565

>>In my experiments, IE is correctly identifying the media and Firefox is
>>not. However I think FF is expecting the content_type to be sent with
>>the media and IE is guess* based upon the media it receives.

I believe this is correct.  Regardless of the content-type header value, IE 
will take an educated guess. FF will not. This would jive with the behavior I 
would expect with an incorrect content-type header.

>>So my question, initially, is can a request set the content_type more
>>than once?

Sure, you can add 10 different content type headers if you want, each with 
different values.  I have no idea what a given browser will do though;-)  The 
answer to your problem seems to be making sure one and only one content-type 
header is returned with the image, and that it has the correct value (e.g. 
Content-Type: image/jpeg or whatever). It would help if you could use something 
like the FF liveHttpHeaders add-on and show us the actual HTTP headers in the 
response for the request "/images/showImage.html?imageid=123456".


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Re: content type headers

[Gunnar Hjalmarsson]

Hellman, Matthew wrote:
The answer to your problem seems to be making sure one and only one 
content-type header is returned with the image, and that it has the 
correct value (e.g. Content-Type: image/jpeg or whatever).


Right, and it just struck me that this is probably a web server 
configuration issue. A sensibly configured server should send the 
correct content-type header out from the file extension.


Please see the attached file, which is the config file for this purpose 
on my own (Apache) server. There you can see that a jpg extension 
results in content-type image/jpeg, a png extension gives image/png etc.


--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl
# This is a comment. I love comments.

# This file controls what Internet media types are sent to the client for
# given file extension(s).  Sending the correct media type to the client
# is important so they know how to handle the content of the file.
# Extra types can either be added here or by using an AddType directive
# in your config files. For more information about Internet media types,
# please read RFC 2045, 2046, 2047, 2048, and 2077.  The Internet media type
# registry is at .

# MIME type Extension
application/EDI-Consent
application/EDI-X12
application/EDIFACT
application/activemessage
application/andrew-insetez
application/applefile
application/atomicmail
application/batch-SMTP
application/beep+xml
application/cals-1840
application/commonground
application/cybercash
application/dca-rft
application/dec-dx
application/dvcs
application/eshop
application/http
application/hyperstudio
application/iges
application/index
application/index.cmd
application/index.obj
application/index.response
application/index.vnd
application/iotp
application/ipp
application/isup
application/font-tdpfr
application/mac-binhex40hqx
application/mac-compactpro  cpt
application/macwriteii
application/marc
application/mathematica
application/mathematica-old
application/msword  doc
application/news-message-id
application/news-transmission
application/ocsp-request
application/ocsp-response
application/octet-streambin dms lha lzh exe class so dll
application/oda oda
application/ogg ogg
application/parityfec
application/pdf pdf
application/pgp-encrypted
application/pgp-keys
application/pgp-signature
application/pkcs10
application/pkcs7-mime
application/pkcs7-signature
application/pkix-cert
application/pkix-crl
application/pkixcmp
application/postscript  ai eps ps
application/prs.alvestrand.titrax-sheet
application/prs.cww
application/prs.nprend
application/qsig
application/remote-printing
application/riscos
application/rtf rtf
application/sdp
application/set-payment
application/set-payment-initiation
application/set-registration
application/set-registration-initiation
application/sgml
application/sgml-open-catalog
application/sieve
application/slate
application/smilsmi smil
application/timestamp-query
application/timestamp-reply
application/vemmi
application/vnd.3M.Post-it-Notes
application/vnd.FloGraphIt
application/vnd.accpac.simply.aso
application/vnd.accpac.simply.imp
application/vnd.acucobol
application/vnd.aether.imp
application/vnd.anser-web-certificate-issue-initiation
application/vnd.anser-web-funds-transfer-initiation
application/vnd.audiograph
application/vnd.businessobjects
application/vnd.bmi
application/vnd.canon-cpdl
application/vnd.canon-lips
application/vnd.claymore
application/vnd.commerce-battelle
application/vnd.commonspace
application/vnd.comsocaller
application/vnd.contact.cmsg
application/vnd.cosmocaller
application/vnd.cups-postscript
application/vnd.cups-raster
application/vnd.cups-raw
application/vnd.ctc-posml
application/vnd.cybank
application/vnd.dna
application/vnd.dpgraph
application/vnd.dxr
application/vnd.ecdis-update
application/vnd.ecowin.chart
application/vnd.ecowin.filerequest
application/vnd.ecowin.fileupdate
application/vnd.ecowin.series
application/vnd.ecowin.seriesrequest
application/vnd.ecowin.seriesupdate
application/vnd.enliven
application/vnd.epson.esf
application/vnd.epson.msf
application/vnd.epson.quickanime
application/vnd.epson.salt
application/vnd.epson.ssf
application/vnd.ericsson.quickcall
application/vnd.eudora.data
application/vnd.fdf
application/vnd.ffsns
application/vnd.framemaker
application/vnd.fsc.weblaunch
application/vnd.fujitsu.oasys
application/vnd.fujitsu.oasys2
application/vnd.fujitsu.oasys3
application/vnd.fujitsu.oasysgp
application/vnd.fujitsu.oasysprs
application/vnd.fujixerox.ddd
application/vnd.fujixerox.docuworks
application/vnd.fujixerox.docuworks.binder
application/vnd.fut-misnet
application/vnd.grafeq
application/vnd.groove-account
application/vnd.groove-identity-message
application/vnd.groove-injector
application/vnd.groove-tool-message
application/vnd.groove-tool-template
appli

RE: content type headers

[Hellman, Matthew]

I don't think that's it's a web server thing, because he's dynamically 
generating the images and not using a .jpg extension. Doing it this way allows 
you do such things as resize the image on the fly using URL parameters. 
Something like:

src="/images/showImage.html?imageid=123456&size=800x600

the HTTP response headers would probably shed the most light on the problem, 
nudge, nudge;-)

>>-Original Message-
>>From: Gunnar Hjalmarsson [mailto:nore...@gunnar.cc]
>>Sent: Thursday, July 02, 2009 1:24 PM
>>To: beginners-cgi@perl.org
>>Subject: Re: content type headers
>>
>>Hellman, Matthew wrote:
>>> The answer to your problem seems to be making sure one and only one
>>> content-type header is returned with the image, and that it has the
>>> correct value (e.g. Content-Type: image/jpeg or whatever).
>>
>>Right, and it just struck me that this is probably a web server
>>configuration issue. A sensibly configured server should send the
>>correct content-type header out from the file extension.
>>
>>Please see the attached file, which is the config file for this purpose
>>on my own (Apache) server. There you can see that a jpg extension
>>results in content-type image/jpeg, a png extension gives image/png etc.
>>
>>--
>>Gunnar Hjalmarsson
>>Email: http://www.gunnar.cc/cgi-bin/contact.pl


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