Hi, If I haven't misread something, this
a = a >> 1; makes no sense. Unless you're trying to divide alpha by 2, in which case I obviously missed something. If you want to extract the 4 components, you can use something like this: var hexaValue:int = 0x9100ff33; var a:int = (hexaValue >> 24) & 0xff; var r:int = (hexaValue >> 16) & 0xff;; var g:int = (hexaValue >> 8) & 0xff;; var b:int = hexaValue & 0xff; var newAlpha:int = 0xcc; var copyHexaValue:int = newAlpha << 24 | r << 16 | g << 8 | b; trace(uint(copyHexaValue).toString(16)); // traces cc00ff33 If you don't bother to get the individual RGB components, just the alpha channel, try this: var hexaValue:int = 0x9100ff33; var a:int = (hexaValue >> 24) & 0xff; var arg:int = hexaValue & 0xffffff; var newAlpha:int = 0xcc; copyHexaValue = newAlpha << 24 | arg; trace(uint(copyHexaValue).toString(16)); // traces cc00ff33 Also, I'm casting to uint just to display the value in a more meaningful/readable way in the trace, but as long as you don't perform arithmetic on those values, you don't have to (because it's parsed as a bit pattern, not as numerical value, if that makes sense...). Cheers Juan Pablo Califano 2008/10/6, sebastian <[EMAIL PROTECTED]>: > > hi Glen, > > Kudos for the shift >> 1 operation, knew that was a faster operand. > > However, this code is still now working, now it simply doesn't change > anything... > :( > > var val:uint = getPixel32(x,y); > var a:uint = (val >> 24) & 0xff; > var rgb:uint = val & 0xffffff; > a = a >> 1; > var newval:uint = (a << 32) | rgb; > setPixel32(x,y,newval); > > I also tried changing it to say: > > ... > var rgb:uint = val & 0x00ffffff; > a = a >> 1; > var newval:uint = (a << 24) | rgb; > ... > > since I thought that was an error maybe, but that also doesn't influence > the alpha of the pixel... > :( > > Out of desperation I also tried: > > var a:uint = val & 0xff000000; > var rgb:uint = val & 0x00fffff; > a = a >> 1; > var newval:uint = a | rgb; > > and > > var a:uint = val & 0xff000000; > var rgb:uint = val & 0x00fffff; > a = a >> 1; > var newval:uint = (a << 24) | rgb; > > :( > > sniff... > > Setting alpha for the whole MC is not an option for what I am doing. I'm > trying to create trails behind things that are moving by having a video-burn > like effect; by operating on the pixel level. At the moment I am using code > from 'Adventures in AS', but once i have it working I'll encapsulate it and > use it in a different project. > > The original source is: > > http://flashcoding.blogspot.com/2008/03/small-starfield-with-bluring-effect.html > > And my current draft-code modification is: > > package > { > import flash.events.*; > import flash.display.*; > import flash.display.Bitmap; > import flash.display.BitmapData; > import flash.geom.Rectangle; > > > public class Starfield > { > var mc:MovieClip =new MovieClip(); > var screendata:BitmapData; > > var stars:Array=new Array(); > var antal:Number=500; > > public function Starfield(timeline) > { > > screendata=new BitmapData(320,240,false,0x00000000); > var screen:Bitmap=new Bitmap(screendata); > mc.addChild(screen); > > for (var i:int=0;i<antal;i++) > { > InitStar(i); > } > > mc.addEventListener(Event.ENTER_FRAME,this.render); > timeline.addChild(mc); > } > > private function MoveStar(index:int) > { > if (stars[index][0]<-160 || stars[index][0]>160 || > stars[index][1]<-120 || stars[index][1]>120) > { > InitStar(index); > } > else > { > stars[index][0]= > stars[index][0]*stars[index][2]; > stars[index][1]= > stars[index][1]*stars[index][2]; > } > } > > private function InitStar(index:int) > { > > stars[index]=[Number(((Math.random()*10)-5)),Number(((Math.random()*10)-5)),Number((Math.random()/10)+1)]; > } > > > private function render(e:Event):void > { > for(var x:int=0;x<320;x++) > { > for(var y:int=0;y<240;y++) > { > > var val:uint = screendata.getPixel32 > (x,y); > > var a:uint = (val >> 24) & 0xff; > var rgb:uint = val & 0xffffff; > a = a >> 1; > var newval:uint = (a << 24) | rgb; > > screendata.setPixel32(x,y,newval); > > } > } > > for(var i:int=0;i<antal;i++) > { > MoveStar(i); > > screendata.setPixel(stars[i][0]+160,stars[i][1]+120,0xFFFFFF); > } > } > } > } > > > Regards, > > Sebastian. > > > Glen Pike wrote: > >> Hi, >> >> I think you need to shift by 24 for alpha, you also need to shift then >> mask the value. RGB is just the bottom three bytes masked and shifting by 1 >> rather than divide by 2 may be faster, but google for the speed comparisons >> in AS3 - I think John Grden may have blogged this: >> var a:uint = (val >> 24) & 0xff; >> var rgb:uint = val & 0xffffff; >> a = a >> 1; >> var newval:uint = (a << 32) | rgb; >> >> It would be a good learning exercise to do your own equations for >> manipulating pixel stuff, but have a look at Mario Klingemann's blog - >> quasimondo.com - for tips and tricks with images as he is one of the best >> people at manipulating bitmaps in Flash so he may have some nice examples to >> stimulate you. For simpler manipulation have a google. Also, if you are >> just setting the alpha to 50% for the whole bitmap, it may be quicker to do >> this on the MovieClip because FlashPlayer might be optimising composition >> somehow, but I understand this may just be an example. >> >> HTH >> >> Glen >> sebastian wrote: >> >>> Thanks Glen and Andrew, >>> >>> Thanks for your fast help, >>> >>> Tried to use this code [below] but it makes my pixels yellow instead of >>> 50% alpha on each pass... any ideas why? >>> >>> Is there any good tutorial on working with bit operations and bit logic? >>> Would make it easier for me to trouble shoot/make my own equations. >>> :) >>> >>> Thanks! >>> >>> Seb. >>> >>> Andrew Murphy wrote: >>> >>>> I'm not sure of this, but: After you grab "val" you could bitshift out >>>> the >>>> alpha channel ("a"), subtract that from the original argb value to >>>> remove >>>> the alpha channel. Manipulate "a" and bitshift it back up again before >>>> adding it to the rgb value to give you a new argb. >>>> >>>> >>>> var a:uint = val >> 32 & 0xff; >>>> var rgb:uint = val - (a << 32); >>>> a = a / 2; >>>> var newval:uint = rgb + (a << 32); >>>> >>>> >>>> >>>> -------------------------------- >>>> Andrew Murphy >>>> Interactive Media Specialist >>>> [EMAIL PROTECTED] >>>> >>>> Delvinia >>>> 214 King Street West, Suite 214 Toronto Canada M5H 3S6 >>>> >>>> P 416.364.1455 ext. 232 F 416.364.9830 W www.delvinia.com >>>> >>>> CONFIDENTIALITY NOTICE >>>> This email message may contain privileged or confidential information. >>>> If >>>> you are not the intended recipient or received this communication by >>>> error, >>>> please notify the sender and delete the message without copying or >>>> disclosing it. >>>> >>>> AVIS DE CONFIDENTIALITÉ >>>> Ce message peut contenir de l'information légalement privilégiée ou >>>> confidentielle. Si vous n'êtes pas le destinataire ou croyez avoir reçu >>>> par >>>> erreur ce message, nous vous saurions gré d'en aviser l'émetteur et d'en >>>> détruire le contenu sans le communiquer a d'autres ou le reproduire. >>>> >>>> >>>> >>>>> -----Original Message----- >>>>> From: [EMAIL PROTECTED] [mailto: >>>>> [EMAIL PROTECTED] On Behalf Of sebastian >>>>> Sent: Monday, October 06, 2008 3:18 PM >>>>> To: Flash Coders List >>>>> Subject: [Flashcoders] working with getPixel32 and setPixel32, >>>>> >>>>> hi folks, >>>>> >>>>> can any one shed some light to me on the setpixel32 and getpixel32? >>>>> >>>>> I'd like to be able to affect just one of the 4 components: A R G or B >>>>> independently of another. >>>>> >>>>> Essentially, read the current ARGB using getPixel32 and then manipulate >>>>> just one part of it, in my case, halve the current "A" value of the ARGB >>>>> and >>>>> then re-assign it back to the bitmap. >>>>> >>>>> >>>>> //1: grab the HEX value for the current coordinate: >>>>> var val:uint = getPixel32(x,y); >>>>> >>>>> //2: manipulate the HEX value of just 1 of the 4 parts, in my case the >>>>> A of the ARGB: >>>>> ???? >>>>> >>>>> //3: re-assign it back to the display: >>>>> setPixel32(x,y,val); >>>>> >>>>> Thanks for your help! >>>>> >>>>> Sebastian. >>>>> _______________________________________________ >>>>> Flashcoders mailing list >>>>> Flashcoders@chattyfig.figleaf.com >>>>> http://chattyfig.figleaf.com/mailman/listinfo/flashcoders >>>>> >>>> >>>> >>>> _______________________________________________ >>>> Flashcoders mailing list >>>> Flashcoders@chattyfig.figleaf.com >>>> http://chattyfig.figleaf.com/mailman/listinfo/flashcoders >>>> >>>> _______________________________________________ >>> Flashcoders mailing list >>> Flashcoders@chattyfig.figleaf.com >>> http://chattyfig.figleaf.com/mailman/listinfo/flashcoders >>> >>> >>> >> _______________________________________________ > Flashcoders mailing list > Flashcoders@chattyfig.figleaf.com > http://chattyfig.figleaf.com/mailman/listinfo/flashcoders > _______________________________________________ Flashcoders mailing list Flashcoders@chattyfig.figleaf.com http://chattyfig.figleaf.com/mailman/listinfo/flashcoders
