BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  How to get DPI for a JPEG file ?          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message yc Guest Posted: Wed Aug 03, 2005 5:47 am    Post subject: How to get DPI for a JPEG file ? Hi, I've been struggling and bogging down nearly for a day unfortunately no good. Is there a way to get the dpi for a jpeg file ? There is no help or doc available at Borland site. Thank in advance yc Back to top Yannis Guest Posted: Wed Aug 03, 2005 8:37 am    Post subject: Re: How to get DPI for a JPEG file ? "yc" <yc (AT) yc (DOT) yc> wrote in news:42f05a65$1 (AT) newsgroups (DOT) borland.com: Quote: Hi, I've been struggling and bogging down nearly for a day unfortunately no good. Is there a way to get the dpi for a jpeg file ? There is no help or doc available at Borland site. Thank in advance yc for any kind of information from most of the file formats I always recomend to take a look on http://www.wotsit.org/ as far as I remember it has at least two documents for jpeg. regards Yannis. Back to top yc Guest Posted: Wed Aug 03, 2005 8:58 am    Post subject: Re: How to get DPI for a JPEG file ? Thanks Yanis, Quite good site Yannis <None (AT) noware (DOT) non> wrote: Quote: "yc" <yc (AT) yc (DOT) yc> wrote in news:42f05a65$1 (AT) newsgroups (DOT) borland.com: for any kind of information from most of the file formats I always recomend to take a look on http://www.wotsit.org/ as far as I remember it has at least two documents for jpeg. regards Yannis. Back to top Joris Van Damme Guest Posted: Wed Aug 03, 2005 11:41 am    Post subject: Re: How to get DPI for a JPEG file ? Quote: Quite good site It used to be. But it's so badly maintained last couple of years, that it hardly deserves us linking to it from our messages anymore... Don't try and find anything recent there, and do double-check anything you find there because chances are that it's outdated and overwritten in the maintained parts of the universe. Today, wotsit.org mainly serves as a vehicle for the screensaver pop-up and pop-under advertissements that seems to be so terribly filthy as to even be able to work around most filth blockers. That's shamefull practice, all by itself. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html Back to top Jim Slade Guest Posted: Wed Aug 03, 2005 12:38 pm    Post subject: Re: How to get DPI for a JPEG file ? "yc" <yc (AT) yc (DOT) yc> wrote in news:42f05a65$1 (AT) newsgroups (DOT) borland.com: Quote: Hi, I've been struggling and bogging down nearly for a day unfortunately no good. Is there a way to get the dpi for a jpeg file ? There is no help or doc available at Borland site. This is not defined by the JPEG standard. The location of the information depends upon the file format being used. JFIF, the most common (search on that) has provisions for including it but the information is often not filled in. I can't remember off the top of my head if EXIF, the other common format (search on tha) has the information. Adobe also has their own file format. Back to top Joris Van Damme Guest Posted: Wed Aug 03, 2005 1:12 pm    Post subject: Re: How to get DPI for a JPEG file ? Quote: This is not defined by the JPEG standard. The location of the information depends upon the file format being used. Confirmed. Quote: JFIF, the most common (search on that) has provisions for including it but the information is often not filled in. Confirmed. Quote: I can't remember off the top of my head if EXIF, the other common format (search on tha) has the information. Not really, see http://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif.html. There is some stuff that is related, but as EXIF is primarilly intended for documenting photographs and the state of the camera as the photograph is taken, the notion of normal DPI as in 'how large does this print' does not make much sense anyhow. Also, even though the EXIF-in-JPEG and JFIF specification are mutually exclusive, strictly speaking, it has become common practice to mix the EXIF info into JFIF files. Thus, even in JPEGs with EXIF, I'd be looking for the typical JFIF encoded DPI instead. Quote: Adobe also has their own file format. I thought Adobe did write JFIF-style JPEGs last couple of decades. They had their own extension in the pre-JFIF days, but I thought they had abandoned that in favor of JFIF. What the original poster needs is a JPEG parser for starters. The following is from the top of my head and may need correction. JPEG is a stream of marker. Each block starts with a variable number of 255 bytes (mostly just one), followed by a marker ID byte. This marker ID byte is not 0 and not 255. If the particular marker type identified by this ID byte has a 'data segment', the next two bytes encode the length of this data segment, the two bytes included, and next comes the data. After that, next marker should start, etc. The actual compressed image data does not comply to the above scheme. If you parse a JPEG with the above scheme, you'll typically see a large block of 'unmarked' data sitting in between two markers, that's the actual compressed image data. From the JFIF spec, which is only a couple of plain text pages, it should be easy to see what market type you need to find to get at the DPI info. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html Back to top Jim Slade Guest Posted: Wed Aug 03, 2005 4:08 pm    Post subject: Re: How to get DPI for a JPEG file ? "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote in news:42f0c2cb (AT) newsgroups (DOT) borland.com: Quote: I can't remember off the top of my head if EXIF, the other common format (search on tha) has the information. Not really, see http://www.awaresystems.be/imaging/tiff/tifftags/privateifd/exif.html. There is some stuff that is related, but as EXIF is primarilly intended for documenting photographs and the state of the camera as the photograph is taken, the notion of normal DPI as in 'how large does this print' does not make much sense anyhow. That was my recollection. Quote: I thought Adobe did write JFIF-style JPEGs last couple of decades. They had their own extension in the pre-JFIF days, but I thought they had abandoned that in favor of JFIF. For the most part except for 4-component JPEGs. They do include their own APPn markers and who knows what goes in them. Quote: Back to top Yannis Guest Posted: Thu Aug 04, 2005 1:03 pm    Post subject: Re: How to get DPI for a JPEG file ? "Joris Van Damme" <PleaseReplyTo (AT) TheGroupInstead (DOT) be> wrote in news:42f0ad69 (AT) newsgroups (DOT) borland.com: Quote: Quite good site It used to be. But it's so badly maintained last couple of years, that it hardly deserves us linking to it from our messages anymore... Don't try and find anything recent there, and do double-check anything you find there because chances are that it's outdated and overwritten in the maintained parts of the universe. Translation I used to like it when I started out but now my knownledge on interested issues to me is bigger and I can find halls in the site and documentation. Ok good for you. Regards Yannis. Back to top Joris Van Damme Guest Posted: Thu Aug 04, 2005 1:37 pm    Post subject: Re: How to get DPI for a JPEG file ? Quote: Translation Translation? It's OK to say you suspect that might be the reasoning behind my statement, it's OK to ask me if that is the reasoning behind my statement. But don't just claim it is, that's not OK. And it's not correct, either. I had nothing to gain from making that statement. It was true resentement for bad maintanance, true resentement for invasive advertising, and a friendly warning to my fellow coders, meant only to be helpful. I'm not going to waste another word on this though, reply what you like, and please ignore any effort of mine to be helpful in the future. Block me, I will always be posting from the same pseudo-address and with the same footer signature, so instruct your news client to ignore my posts, please. Joris Van Damme [email]info (AT) awaresystems (DOT) be[/email] http://www.awaresystems.be/ Download your free TIFF tag viewer for windows here: http://www.awaresystems.be/imaging/tiff/astifftagviewer.html Back to top Yannis Guest Posted: Fri Aug 05, 2005 6:34 am    Post subject: Re: How to get DPI for a JPEG file ? I am sorry if I offended you, it wasn't my intention. Regards Yannis. 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