Re: [PEPr] Call for votes on Images::JpegMarkerReader

Thanks for the info. :-) Appreciate it! On Wed, Jun 11, 2008 at 3:29 PM, Tom Boutell <tom@punkave.com> wrote: > Sure. > > Every JPEG file is structured as a collection of markers. So to > discover interesting things about a JPEG file, you need to be able to > read markers. By creating a low-level marker reader class > (Image_JpegMarkerReader), I've provided an easy way to "scroll > through" a JPEG programmatically, looking for information that's > relevant to your application. > > This becomes useful when you want to build something like > Image_JpegXmpReader, which extracts Adobe's XMP metadata from a JPEG, > giving you the title, description, tags, etc. that the user chose to > describe the image (usually in Photoshop). XMP metadata lives in a > particular JPEG marker (APP0), with a particular prefix identifying it > specifically as XMP (there are other uses of the APP0 marker, with > their own signatures). > > I separated the marker-reading and XMP-reading functionality into > parent and child classes so that other programmers can build other > interesting JPEG-related tools that also parse JPEGs via > JpegMarkerReader. > > -Tom > > On Wed, Jun 11, 2008 at 8:44 AM, till <klimpong@gmail.com> wrote: >> Hey Thomas, >> >> can you explain briefly what markers are and what they are used for? I >> couldn't figure this out. >> >> Till >> > -- Till Klampaeckel e: mailto:klimpong@gmail.com p: +491704018676 l: http://beta.plazes.com/whereis/till Want to know what's up in Berlin? - http://berlin.metblogs.com