There really isn't any way to prevent the client side from saving the images. You can impede some users by intercepting a right-button down event, thus disabling the "save image" option. Smart users will avoid this impediment in obvious ways.
You can also create an "image server" URL which accepts authentication & authorization tokens in POST or GET requests and returns the images from a private directory. Note that once the image is "in the browser" it can be copied to local storage. Not that you are employing DRM, but there exists a congruence of your request to DRM: if it can be displayed, it can be copied; which is a fundamental DRM weakness. If you don't trust your users, web-based image distribution is not appropriate for your application. You will have to consider other ways of distributing these images than a web browser. On Feb 18, 8:45 pm, Charlie <[email protected]> wrote: > Your suggestion is certainly needed on the one hand as making the > images no longer viewable on the http server side; but on the other > hand, how about the images already downloaded or cached in the browser > (for the cache stuff, maybe last modified date can help) But I guess > there is really no mechanism to prevent from downloading the images on > the user side and then they can spread it as they wish. I just wish I > can have a hard cut-off date on the images and after certain days the > images themselves can turn into all white pixels or alike. > > Thanks for the thought. > > On 2月18日, 下午7时05分, jchimene <[email protected]> wrote: > > > On Feb 18, 8:44 am, Charlie <[email protected]> wrote: > > > > Sorry for this very off-topic question. But is there any mechanism to > > > set up expiration date on image, and after that date the image won't > > > be viewable, just like injecting a virus into the image. > > > > Or if not image format, is Flash capable of doing that? > > > > Thanks for any thoughts, > > > Charlie > > > The way I've done this in the past is to have a Perl script in a cron > > job that sweeps directories and overwrites content with appropriate > > "expired" content (.html with such text or .jpg with such content). > > The issue is that Apache (or whatever your httpd) needs to be trained > > to return other content after the as-of date. That's a bit much to > > impose on the httpd server. The replacement text is there to avoid > > 404s --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Web Toolkit" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/Google-Web-Toolkit?hl=en -~----------~----~----~----~------~----~------~--~---
