tag:blogger.com,1999:blog-8904768098307558342.post2452594836078710923..comments2020-07-01T03:49:31.777-07:00Comments on Forensic Multimedia Analysis Blog: Blending Mode Math - Part 2Jim Hoerrickshttp://www.blogger.com/profile/07370775585003351900noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-8904768098307558342.post-87415414605596914052009-12-21T14:45:48.101-08:002009-12-21T14:45:48.101-08:00This note concerns the formulae for Screen and Sof...This note concerns the formulae for Screen and Soft Light. Both are in error!<br /><br />Screen: A comment by "xeption" shows the formula can not be right.<br /><br />The way to think about this is via decimal fractions. If L and U are tone values, between 0 and 255, let U% = U/255 and L% = L/255 denote the "fraction of white" in a tone.<br /><br />The product L%*U% always Unknownhttps://www.blogger.com/profile/08865531761194774488noreply@blogger.comtag:blogger.com,1999:blog-8904768098307558342.post-47371033972499446522008-09-23T02:37:00.000-07:002008-09-23T02:37:00.000-07:00Soft Light and Overlay -http://www.modelmayhem.com...Soft Light and Overlay -<BR/><BR/>http://www.modelmayhem.com/po.php?thread_id=349057<BR/><BR/>These are the results of my experiments. Not sure if they check out mathematically, but they look approximately right.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8904768098307558342.post-27485705382003653372008-08-15T09:17:00.000-07:002008-08-15T09:17:00.000-07:00"In your formula, the top and bottom 255 would can..."In your formula, the top and bottom 255 would cancel each other out." what do you mean they would cancel each other out ?! cancelling each other out would happen if there was 255 * ((255-U)*(255-L))/255 no? but that is 255 (minus) ((255-U)*(255-L))/255 .... sorry for being a newbieAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-8904768098307558342.post-17814163188582968132008-08-15T09:12:00.000-07:002008-08-15T09:12:00.000-07:00I've used this formula to achieve the overlay effe...I've used this formula to achieve the overlay effect (which is actually screen effect over multiply effect) in PHP through GD library, and if the formula is with 1- then all the values I get are negative and then they're automaticly set to zero (as you recommanded a few lines back). At first I tried to multiply those values with -1 and see what i get but the result was something like inverting Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8904768098307558342.post-6452242065626842472008-08-15T05:24:00.000-07:002008-08-15T05:24:00.000-07:00plug the numbers in and show your work. In your fo...plug the numbers in and show your work. In your formula, the top and bottom 255 would cancel each other out. Try it.Jim Hoerrickshttps://www.blogger.com/profile/07370775585003351900noreply@blogger.comtag:blogger.com,1999:blog-8904768098307558342.post-83480102529998954522008-08-15T04:49:00.000-07:002008-08-15T04:49:00.000-07:002 things:1. I LOVE YOU!2. for Screen Effect the fo...2 things:<BR/>1. I LOVE YOU!<BR/>2. for Screen Effect the formula is actualy 255 - ((255-U)*(255-L))/255Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8904768098307558342.post-75851240461197394942008-06-19T15:22:00.000-07:002008-06-19T15:22:00.000-07:00Totally awesome reference. Saved me a few hours i...Totally awesome reference. Saved me a few hours investigation! Thanks.Anonymousnoreply@blogger.com