On Dec 30 2010, 6:23 pm, Sripathi Krishnan <sripathi.krish...@gmail.com> wrote: > *re. 1 - Best way to transfer* > IMHO - Base64 encoded data in either JSON or XML, with standard gzip > compression applied. Optionally (but recommended), rename the files to > <MD5>.cache.xml or something similar, and set strong http cache headers. > OK, will use Base65 encoded data with XML.
> If ... you have the files at compile time, you can should consider using... Nope these files are data, coming from a server. The aren't know at compile time. > > Base64 is the preferred format because you can directly render the string on > a canvas using > data:uri<https://developer.mozilla.org/en/Canvas_tutorial/Using_images#section_5>. Interesting, this is a bonus. I'm not sure this case could use it though. The data is gray-scale with no transparency, so instead of 4 bytes for RBG and alpha, it will just be just one 15-bit gray scale value per pixel. Also the scaling needs to take place and I'm thinking of doing that on the client side. Is the canvas only 8 bit grey scale? (256) > You should also read Google Instant Previews Under the > Hood<http://googleblog.blogspot.com/2010/11/beyond-instant-results-instant...>- > it explains how google transfers images using base64 encoding to the > browser. > OK will need to read this. > *re. 2 Best way to store client side* > Since you are targeting HTML5 capable browsers, localStorage seems the best > solution. It has decent browser support, but the only caveat is that > localStorage > can only store strings, not > objects<http://diveintohtml5.org/storage.html#methods>. > This is another reason to use base64 encoded strings - they can easily be > stashed into localStorage and consumed without much ado. I see that the limit is 5 mega-bytes per site for HTML5 local storage from the link. That likely will likely hold 5-10 of these images, but it would need to be more like 100 to 200 images. Would a browser have an issue with 100 canvas tags each holding one image, and only one that is visible as a time? This only needs to run in Chrome, and Safari and Firefox are optional. Does Chrome have a 5 megabyte limit? > > --Sri > > On 31 December 2010 06:05, ams <alan.sny...@gmail.com> wrote: > > > > > > > > > I'm working with medical images 500 slices typically 512x512 gray > > scale that I would like to pre-fetch and display/manipulate in an > > HTML5 canvas element. The files will typically be local, but since > > this is GWT it will (as fas a I know) needs to be sent from the > > server. > > > Since I'm using HTML5 this will target Chrome first, but I'd like to > > support Safari and Firefox. IE (even version 9) can go take a hike. > > > I'm looking for opinions here an three questions. > > > #1) What is the best way to transfer down (pre-fetch 500) binary files > > (array of integers). Sending down an text array with int values seems > > in efficient. This article about sending the file down encoded in XML > > seems the best option I've found, but want to know if others here have > > a different opinion. > > > Transfer binary data in an XML document > >http://javaworld.com/javatips/jw-javatip117.html > > > #2) The second question is how to store this data on the client side. > > It likely will be the HTML5 Web Storage API as implements currently on > > Chrome, but I'd like to here others thoughts on this. > > > #3) Also, I'm going to need to scroll through this images rather > > quick, so was was thinking about have a bunch of canvas tags with > > images preloaded, but only one visible at a time. An alternative it > > have only one canvas take and draw on that anytime someone wants to > > scroll though them. Which would be faster? > > > Thanks. > > > -- > > You received this message because you are subscribed to the Google Groups > > "Google Web Toolkit" group. > > To post to this group, send email to google-web-tool...@googlegroups.com. > > To unsubscribe from this group, send email to > > google-web-toolkit+unsubscr...@googlegroups.com<google-web-toolkit%2Bunsubs > > cr...@googlegroups.com> > > . > > For more options, visit this group at > >http://groups.google.com/group/google-web-toolkit?hl=en. -- You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to google-web-tool...@googlegroups.com. To unsubscribe from this group, send email to google-web-toolkit+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-web-toolkit?hl=en.
