PNG premultiplied Alpha

Has anyone come up with a solution for exporting PNGs with premultiplied alpha?
SuperPNG used to do this in older versions by using the Photoshop alpha channel for transparency, but the new version appears to use layer transparency (much like Photoshop's PNG & Save For Web PNG export).
The old version also appears to be incompatible with CS3+

Hello Mr Cox,
Thank You for your reply.
Chris Cox wrote:
PNGs are not premultiplied, and are saved as straight color/alpha from Photoshop.
PNG does not support alpha channels, only transparency.
Do you mean that PNGs dont support alpha channels at all? Or just in Photoshop? These two sentences are confusing.
I understand that transparency and alpha channels are different thing, but I want to make files transparent and with alpha channels.
If PNG is not premultiplied why video export has an option to premultiply PNG alpha with black/other color? Its really confusing!
What I have been doing to this day:
1) I have made a graphic "x" on transparent background.
2) I selected the layer and ran action "Alpha Channel from Visible Layers".
3) Then I have made full black layer under the graphic "x".
4) Then used superPNG plugin to intergrate Alpha 1 channel(made by action) within png file.
Programmer i work with says that the files I gave him worked like premultiplied alpha pngs, he wrote custom scripts and shaders and he says that these were ok. I am really confused now.
So as You see I'm really torn right now! I have red parts of PNG speciffication, everything on wikipedia about PNGs and alpha composing etc. and some other articles around web and I feel just stupidier. Could You recommend me a good read about this topic or elaborate more? It could be a book or anything.
Best regards,
Peter

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Linda,
I do not appreciate your condescending tone. I have attempted all of your instructions. Embedded is a window capture of my graphic on a TRANPARENT canvas with your suggested settings. Also embedded is the resulting graphic. Finally, embedded is the original graphic that demonstrates what I am attempting to achieve.
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I have the following problem:
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[svn:fx-trunk] 11073: Updating LuminosityMaskFilter. pbj to correct the PixelBender code to account for the fact that the mask artwork is in premultiplied alpha form .

Revision: 11073
Author:   [email protected]
Date:     2009-10-21 18:29:07 -0700 (Wed, 21 Oct 2009)
Log Message:
Updating LuminosityMaskFilter.pbj to correct the PixelBender code to account for the fact that the mask artwork is in premultiplied alpha form.
QE notes: N/A
Doc notes: N/A
Bugs: N/A
Reviewer: Dan
Tests run: Dan's luminosity test case.
Is noteworthy for integration: No
Modified Paths:
    flex/sdk/trunk/frameworks/projects/spark/src/spark/primitives/shaders/LuminosityMaskFilte r.pbj

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Hello to everyone.
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I need to output my file as a PNG with an ALPHA Channel for the web. First, I created an alpha for my image, and then I tried to simply use the "save as" function and select the PNG format, but the ALPHA selection is grayed out. I've also tried "the save for web function" and selected transparency, but when I reopen the file the alpha channel has dissappeared. I know that it is possible to save an alpha channel to a PNG, but I can't seem to do it with Photoshop... Can anyone help?
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Hi.
I have a 15 minute movie that I've edited in FCP7.
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FCPX is doing funny things to PNGs with alpha channel.

I am currently working on a video that requires lots of compositing using PNGs with transparency. Everything was fine, until I decided to render. Then this happened:
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I've tried:
Trashing Render Files
Changing Alpha Handling
Export without Render
Using "Add" as the Blend Mode.
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I suggest you begin by deleting preferences, as so many weird things seem to be caused by corrupt preferences.
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Why can't I export a 24 bit PNG with alpha transparency?

I have just upgraded my Macromedia Studio 8 to Adobe CS3, and
it seems that I still can't export a 24 bit png with transparency
from Fireworks (Photoshop can do it, but it's just not suited for
volume graphic production). Anyone know something I don't, or can
someone at least explain why I can have alpha transparency on 8 bit
and 32 bit, but not 24 bit pngs? Currently, I'm planning to export
everything from Fireworks, then batch-process through Photoshop to
reduce from 32 bit to 24 bit, which is just... gah! Words fail
me.

Kathleen13 wrote:
> I have just upgraded my Macromedia Studio 8 to Adobe
CS3, and it seems that I
> still can't export a 24 bit png with transparency from
Fireworks (Photoshop can
> do it, but it's just not suited for volume graphic
production). Anyone know
> something I don't, or can someone at least explain why I
can have alpha
> transparency on 8 bit and 32 bit, but not 24 bit pngs?
Currently, I'm planning
> to export everything from Fireworks, then batch-process
through Photoshop to
> reduce from 32 bit to 24 bit, which is just... gah!
Words fail me.
>
If I'm correct, 8-bit png supports index transparency just
like GIF's
do. 32-bit png's support alpha channel transparency, so you
can get
variable or partial transparency in a full color image(8 bits
for each
color and 8 bits for an alpha channel) and 24-bit png's are
similar
jpegs, only you get lossless compression and no user-defined
settings.
So essentially, when you export a 32-bit png file you are
exporting a 24
bit color image with an 8-bit alpha channel.
Jim Babbage - .:Community MX:. & .:Adobe Community
Expert:.
Extending Knowledge, Daily
http://www.communityMX.com/
CommunityMX - Free Resources:
http://www.communitymx.com/free.cfm
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Help: importing PNG's Alphas to make a sprite sheet

Hi All,
I need some help with making PNG sprite sheets with Photoshop CS4 Extended.
The issue is with Photoshop. When I bring in the PNG animation sequence image 1 then 2 I lose the alpha after that.
What is the best way to bring in multpel alphas to make a sprite-sheet? The trick I have used so far has given me
bad results.
* Note: I have rendered out 35 frames of an animation sequence from 3Ds Max 9 as .PNGs & .TGAs with alphas.
Thanks in advance :-)
My curent way of doing this is:
Steps:
1. Launch Photoshop CS4 Extended
2. Set document size to 256X512
3. Set up a grid 32X32 pixles
4. Open Frames 1 to 35 of animation
5. place frames in order on sprite sheets
Note: open "Channels Panel" observe only the 1st frame has an alpha
And my work-around is to do the same steps for the alpha by opening each frame in Photoshop and going in the Channels tab and selecting just the alpha layer. Then copy and pasting it into new photoshop document to make the sprite sheet's alpha. Once
the alpha sprite sheet is done copy and paste it into the original sprite sheet document.
This sounds like a lot of steps and it is...

Hey All,
Thanks for posting :-)
Hi Chris Cox,
The PNG format out of Photoshop does not work in computer game graphics for some reason so the game artist use SuperPNG. To get SuperPNG to work it must have an alpha channel for the transparency to work in game engines like GameMaker & GarageGames.
HI Paul Riggott,
I am using a software tool like File Sticher called GlueIt and it is working great for me. But this is one extra step I am trying to remove to my art pipe-line.
Here is the current result in the GameMaker v7.0
Here is the my current work flow in Photoshop CS4 Extended

PNG alpha import bug - doesn't ask, interprets always as straight

This has been an issue for quite some time now, finally found time to search for a solution and couldn't find one
If I render a scene in 3dsMAX and save it as a PNG file, then I import it to AE, AE doesn't ask what type of alpha is in the image - it always assumes it's straight which is wrong because it's always premultiplied (coming from 3ds MAX at least).
It asks with tiffs, tga, jpeg2000 but NOT with pngs
Any thoughts on that?
If you want to check yourself, maybe on a different 3D software:
- create a plane
- give it a self illuminating red material (so that there is no shading whatsoever)
- throw a black and white gradient to the transparency slot
In AE if you import correctly, on the transparency grid, you'll get a plane of constant red color gradually fading out. If it seems that the more transparent the plane gets, the darker/brighter the red also gets - you have a wrong alpha interpretation.

I never render anything premultiplied from any 3D app. You don't get as good an edge and unless you are specifically using a colored background as a target it makes not sense in a production environment to be using premultiplied alphas. All NLE's default to straight and in almost every case, you get a much better edge.
That said, Dave's right, it's a preferences setting. I have not checked png's or png sequences so I don't know if my machine would show this problem, but then again, I never intentionally produce a premultiplied alpha.

Photos app bug resurrects long-removed photos (related to PNG alpha)

Wanted to report/discuss a possible privacy concern and image glitch, and understand it better for submission to Apple's feedback page: the iPad (and maybe iPhone) Photos app will consitently resurrect long-deleted photos in your Camera Roll, under certain circumstances. These are long-removed photos (as in removed many months ago, prior to the iOS 5 update), and possibly only the reduced-size thumbnail versions.
Note: as near as I can tell, the deleted photos were NOT originally from the camera roll! That's where they resurface, but I believe they are photos from other albums, maybe once which used to by synched to iPad but which I no longer synch. So "removed" might mean deleted or it might mean "no longer synched to iPad"... the images are so old I can't recall.
So the bug, I'm guessing, it two-fold:
1) The Photos app (and/or iPhoto during wired synch?) is not fully removing photos (or at least, their thumbs). They're no longer visible in Photos app, but are being retained somewhere on the device.
2) A glitch in the Photos camera roll PNG handling (which I think may be new with iOS 5) causes those old images ro re-surface when you add a PNG to the camera roll. (The old photos were JPEG, but the image that triggers the bug must be a PNG with alpha channel)
I have seen this on both an iPad 1 and iPad 2, running iOS 5.
Here's how to reproduce it:
1) Synch some photos to your iPad, then deselect them for synching and re-synch (so they're not there any more). Also, add some photos or screenshots to the camera roll and then delete them. I say to do both because I'm not 100% where the old photos come from, and I'm hoping this covers all bases! Actually, most people have already done these things in the past, and can probably skip this step.
2) Generate a transparent PNG using the art app Procreate (and probably any app that saves PNGs to the camera roll with alpha channel). All you have to do is scribble somethign into a blank Procreate canvas, then export it to your photo album. There is no need to do anything special to get an alpha channel or PNG format: you always get that. (Unless you used the Fill command to completely cover the canvas.) Now in the camera roll there should be your scribble on a transparent background. You can email it to yourself and see that clearly in Photoshop or Preview.
3) Here's the glitch: look at your camera roll (thumbnails view) and you'll see that the alpha-transparent background of the image has become one of your old removed photos! Tap it to enlarge and the alpha becomes black (which is fine, although it may seem odd if you intended to paint onto the default white canvas). But for just a moment, before you see the black, you will get a full-size glimpse of the old photo. (Or, maybe, an enlargement of the thumbnail?)
4) If you keep saving more alpha PNGs, you'll keep seeing more and different old photos coming back to life in the alpha regions of the thumbnails (and, briefly, at full size).
5) If you delete all those PNGs and then save some new ones, you'll see the same sequence of old photos reappear again.
Needed fix: removed phtos/thumbnails should be properly purged, and alpha PNGs should show simply black (or some default background) at all times.

Ok, I replicated it and I don't like it! I didn't use the one you marked cause I couldn't call it up properly but I did Bing
transparent gifs and loaded up 3, one was totally invisible in the thumbnail and I could clearly see one of my pics perfectly in the thumbnail but when I brought it to page the gif filled the frame.
I have no idea where the pic came from, I mean I recognize it but from where in the album I have no idea.
Oh yeah, I was wrong about the first pic coming to page, it wasn't the same image but a different one...and I have no idea how the one that came up, (what i thought was the underlying pic) did, or how it got there or even from where.
This is some weird stuff though not as weird as that silly *** movie, what a load of tripe; I should have just spent my
time on this, it's infinitely more enjoyable!
Ok, here's the consensus from my layman iPad view:
What happened now and most probably before was a 'transparent gif' or a partially transparent gif like the one I spoke of first that I could see the edge of or the outer perimeter of, the underlining image with the gif taking up say 3/4 of the thumbnail; this it what it was.
This is totally apparent to me now because of your having me import a totally transparent gif which was invisible over my pic, thus the freaky part I didn't like...keying the thumbnail with one thing and ending up with something totally different when brought to page.
Still doesn't explain where this silly iPad is grabbing these pics from?
But here's something funny; my camera roll shows say 9,200 pics but my, 'iMy System' app say I have like 11,300 which I always thought was a fluke, that it was just reading wrong but maybe it's seeing something we're not. What if all those pics we're deleting to save space or just generally culling have never left the system? Maybe that goofy app is really reading the true count!
Those others up above us here who mentioned privacy concerns.. this could be whats going on, there's a ghost
in the machine and it be our old pics and god knows what else floating around in that iPads memory.
Ok, I'm crazy tired and I have to wrap this up. Least now we know how to replicate this but on the other hand I think we opened up an even bigger can of worms... the mystery of where all those images are hiding in our iPads?
I haven't hardwired to a computer since I upgraded to ios5 so whatever's going on here, leastwise for me is iPad
based and can't be blamed for synching issues like you discuss up above unless what I'm grabbing here is old stuff
reimported back into my pad from the mainframe when I was backed up for the ios5 upgrade?
Oh well, let me know what you think. Please do forgive my not getting back to you sooner on account of the movie
but you already know I regret choosing that over this! Hope you had a good night and thanks...

PNG premultiplied Alpha

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