Re: how to determine the actual file format of an image file?
This WebDNA talk-list message is from 2002
It keeps the original formatting.
numero = 44603
interpreted = N
texte = on 10/30/02 12:40 PM, Frank Nordberg at frnordbe@online.no so noted...> Unfortunately the MIME type won't be much more reliable than the file > extension in this case. There are still one or two Windows computers out > there on the web, and apparently their browsers just set the MIME type > according to the file extension anyway.I'm a little spoiled because the site that's receiving the uploads gets the majority of traffic from Macs, and the browser is setting the MIME type from the internal type/creator codes (and many of the uploaded files don't have extensions in the filename itself).If WebDNA could process null characters, you could include the file in question and check the file headers there.One possibility to get around that limitation would be to encrypt the file as base64 and check for the appropriate encoded text.[showif [getchars start=1&end=4][encrypt method=base64&file=mysteryFile.zzz][/encrypt][/getchars]=R0lG] We have a GIF! [/showif][showif [getchars start=1&end=17][encrypt method=base64&file=mysteryFile.zzz][/encrypt][/getchars]^SkZJRg] We have a JPEG! [/showif]R0lG and SkZJRg being the base64 encodings of GIF and JFIF respectively.Not extensively tested, but perhaps a place to start. Rob Marquardt Designer/Resident Wirehead Toast Design800 Washington Avenue North Minneapolis MN 55401 612.330.9863 v 612.321.9424 f www.toastdesign.com ------------------------------------------------------------- This message is sent to you because you are subscribed to the mailing list
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on 10/30/02 12:40 PM, Frank Nordberg at frnordbe@online.no so noted...> Unfortunately the MIME type won't be much more reliable than the file > extension in this case. There are still one or two Windows computers out > there on the web, and apparently their browsers just set the MIME type > according to the file extension anyway.I'm a little spoiled because the site that's receiving the uploads gets the majority of traffic from Macs, and the browser is setting the MIME type from the internal type/creator codes (and many of the uploaded files don't have extensions in the filename itself).If WebDNA could process null characters, you could include the file in question and check the file headers there.One possibility to get around that limitation would be to encrypt the file as base64 and check for the appropriate encoded text.[showif [getchars start=1&end=4][encrypt method=base64&file=mysteryFile.zzz][/encrypt][/getchars]=R0lG] We have a GIF! [/showif][showif [getchars start=1&end=17][encrypt method=base64&file=mysteryFile.zzz][/encrypt][/getchars]^SkZJRg] We have a JPEG! [/showif]R0lG and SkZJRg being the base64 encodings of GIF and JFIF respectively.Not extensively tested, but perhaps a place to start. Rob Marquardt Designer/Resident Wirehead Toast Design800 Washington Avenue North Minneapolis MN 55401 612.330.9863 v 612.321.9424 f www.toastdesign.com ------------------------------------------------------------- This message is sent to you because you are subscribed to the mailing list . To unsubscribe, E-mail to: To switch to the DIGEST mode, E-mail to Web Archive of this list is at: http://search.smithmicro.com/
Rob Marquardt
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