P: Export as 8-bit PNG issue

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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When using the export as dialog the 8-bit (smaller file) is no longer functioning first screen shot is the Export as dialog in PS 23.1.1 Second is same file and same dialog in 23.2.0PS231.pngPS232.png

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Adobe Community Professional ,
Feb 23, 2022 Feb 23, 2022

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Are you referring to the drop shadow difference in the two?

Can you show the results of the two AFTER using Export As?


Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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yes the drop shadow loses transparency as seen here in the .pngs Same file in both versionsPSProblem.pngPSProblem2.png

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Adobe Community Professional ,
Feb 23, 2022 Feb 23, 2022

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Not seeing this on my Mac:

ExportAs.jpg

If you disable GPU in preferences, any difference?


Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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PC Windows 10 21H2  64 bit all updates Intel i9-9880H Nvidia RTX2080 Same result with GPU disabled

same issue with guassian blur 

chrisn50837302_0-1645645428763.png

 

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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save for web and quick export deliver same results 

chrisn50837302_0-1645645725220.png

 

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Adobe Employee ,
Feb 23, 2022 Feb 23, 2022

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Turn on Transparency Dither in Save for Web.


Senior Product Manager - Customer Advocacy - Digital Imaging

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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not even close to the same. Export as has worked fine up until this version I use it all of the time. something broke.

chrisn50837302_0-1645646226477.png

 

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Adobe Employee ,
Feb 23, 2022 Feb 23, 2022

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@chrisn50837302 We fixed a bug with the Smaller File (8-bit) setting in Export As. In the past, when you had semi-transparent pixels in your file it would create a 24-bit file (RGB) which effectively means it is ignoring the Smaller File setting.

 

Smaller File (8-bit) means the files are supposed to be Index color (like a GIF) and only have one swatch in the color table for transparency. This means the pixel is either fully visible or invisible. Unfortunately we do not currently have a dither settings to create the illustion of falloff for smoother transitions. Hopefully we can get that added in the near future. 

 

@thedigitaldog The reason you are seeing the old behavior is you are using the Legacy version of Export As, which still has this bug (the exported file will be RGB, not the smaller 8-bit that the selected option is supposed to give). 

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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hard to buy that explanation...here is the result of one of my actual files...both exported in 23.1 one in 8-bit and they both look perfect ( the 8-bit does show some pixelation but not in the transparency) so what is reducing the file size yet keeping the transparency? 

chrisn50837302_0-1645650792756.png

chrisn50837302_2-1645651047362.png

 

 

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Adobe Employee ,
Feb 23, 2022 Feb 23, 2022

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The purpose of the Smaller File (8-bit) setting is to export a PNG file in Index Color Mode (just like a GIF file). 8-bit means it is using a indexed color table with 256 total colors. If you do not have this option on, it exports a 24-bit file in RGB Color Mode (just like JPG file). (Technically, the files are 32-bit if the Transparency option is on, but that is just another layer of confusion that we can ignore for now)

 

This can be a bit confusing since we generally refer to JPG files as being 8-bit. But what we mean when we say that is "8-bits per channel" (8 for R, 8 for G, and 8 for B). Another way of expressing this is to say it is a 24-bit file (8-bits X 3 channels = 24). So, having this option OFF should create an RGB color mode file while having this option ON should create an Index color mode file. This setting is not a compression method to make the file size on disk smaller (although that can be a result). 

 

The bug was that when a file contained partially transparent pixels (Opacity 1-99%) the file would export as 24-bit RGB even when this option was on (effectively ignoring this option altogether, giving you the same results as though you had left the option off). 

 

To check, open your exported files in Photoshop and go to Image > Mode. You can see whether a file is in RGB or Index color mode. If you were happy with your previous results while this bug was in place and RGB files are acceptable for your output, then you are not likely using this setting for its intended purpose and leaving it off is probably what you really want. 

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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I understand all of that, i just thought you had some compression going on in the export as option that was reducing the file size (which is what i wanted) as you can see the file size is CONSIDERABLY smaller when using the "smaller file size option" yet still gives me useable transparency results. I'm not here to discuss RGB vs. index I do understand that and agree with you (i assumed that the box meant 8 bit AND/OR smaller file size because it never made an index file), what I want is a reduced size on disk rgb file which I used to get with the previous version. Can you tell me a way to achieve the same smaller file size with the latest version of Photoshop? I'm all for learning a new way to do things.

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Adobe Employee ,
Feb 23, 2022 Feb 23, 2022

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There was never any special compression behind the Smaller File setting. It was always just supposed to make Index files (which are smaller that RGB files by their very nature, hence the name). If you export a flattened image, one with a solid background and no transparency, then you would correctly get an Index file with this setting.

 

Any size difference between having this option on or off when the bug was present would probably come from Photoshop attempting to convert to Index and tossing out a lot of color information until it got to the semi-transparent pixels and convertinging things back to RGB, creating an unintended type of compression. This would be extremely lossy, which is against one of the hallmark features of using PNG files (which use lossless compression normally).

 

[When I look at a file with this type of buggy conversion, I can see a dither applied to these transparent areas, such as when doing an Index conversion. This results in a lower quality (thus smaller file size) version of what the RGB setting provides.]

 

There are a few things I can suggest, depending on what you are really trying to accomplish. First, if you are just trying to get smaller file sizes with an RGB PNG with semi-transprent pixels, Save As (a Copy) is probably your best bet. You have three compression options and when you use the smallest file size setting there, you get even smaller files, the transparency you are looking for, and no index conversion-like dither (which means higher quality appearance). Save for Web is the next best option, since it gives you much better controls for managing the compression settings. Last, you can switch back to the old version of Export As where the bug is still present in Preferences > Export by checking "Use legacy 'Export As'" (not recommended). 

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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thank you, i wish that worked. the save as option took my 192kb file and made it 38 Meg! using all three options

chrisn50837302_0-1645662854046.pngchrisn50837302_1-1645662893409.png

 

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Adobe Employee ,
Feb 23, 2022 Feb 23, 2022

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From my testing (a simple file with a single layer which doesn't cover the entire canvas and a feathered edge, thus semi-transprent pixels) would result in this:

  • Export As PNG (RGB) - 23 MB
  • Export As PNG (buggy Index) - 10 MB
  • Save as PNG (RGB, small size) - 8 MB

I'm assuming your file is more complex and there is a simple explanation for why you are seeing such a huge file size difference. My best guess is that you are working with artboards and Export As is only exporting your specific artboart which is a small part of the whole, but Save As is saving the entire file (all artboards) and thus contains much more information. 

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Explorer ,
Feb 23, 2022 Feb 23, 2022

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No artboards in use. I have done hundreds of these files. they have never been over 200K .png's They are used in a mobile game and never had an issue. The Save as makes them enormous with no explanation. So looks like export as is still the ONLY option...but over 400 k now. The bug you "fixed" should have just been called a "feature" imo.

 

What is the difference between save a copy .png "smallest file size" and export as png 24 bit with transparency (so honestly 32 bit) that would cause the file to bloat from around 500k (expotrt as) to 38Meg (save a copy .png)? same file, should be the same (or close) compression after all they are both .pngs created from the same .psd. Plese explain?

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Adobe Employee ,
Feb 24, 2022 Feb 24, 2022

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Would you be able to share a file where you are seeing this behavior (Save As makes bigger files than Export As)? I'd like to see if I can recreate the behavior on my end and see what the root of the issue is and provide a solution.

 

When you Save As a PNG, the three options you have for Large, Medium, and Small size deal with how PNG compression works. You'll note that each is paired with a Fast, Medium, and Slow save speed. What is happening is that the file is actually compressed using multiple different methods and the most appropriate results are the one you end up with. Large/Fast means it only tries a couple methods and returns the highest quality result. Smallest/Slowest means it tries many methods and returns the smallest file size. Export As doesn't give you a similar choice. Smaller File (8-bit) is not equivalent to Smallest file size (Slowest saving), instead it is the same as using the PNG-8 setting in Save for Web. 

 

Obviously, this all can become confusing. There are often different ways to accomplish the same task in Photoshop, each with different advantages/disadvantages. Terms in one method may sound like terms in another but mean something else (sometimes subtly and other times drastically). 

 

It is quite common for bugs to turn into exploits (people taking advantage of something not working the way it is inteneded but getting some side benefit). When these things get fixed it can remove a workflow people have come to depend on. But remember, there were people who were trying to use the Smaller File setting and expecting (correctly) that they should end up with an Index file and then wondering why some of their files export accurately and others did not. 

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Explorer ,
Feb 24, 2022 Feb 24, 2022

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Sure I can do that, but this is not a place I want to post my company .psd files. can I send them to you through another method?

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Adobe Employee ,
Feb 24, 2022 Feb 24, 2022

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Email me the file(s) or a link to them: bnemecek [at] adobe [dot] com

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Community Beginner ,
Mar 01, 2022 Mar 01, 2022

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I am now having this problem again in the most recent update, 23.2.1, PNG-8 no longer will save any partial transparency and is giving my images jagged edges. Enabling legacy "Export As" in the preferences does work as a work around for now at least.

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New Here ,
Mar 04, 2022 Mar 04, 2022

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Hello there!

I recently noticed a quality decrease when exporting 8-bit PNGs using the Export As function. In January, the exports looked crisp and maintained a drop shadow. Today the lines are jagged, and the drop shadows disappear. Is this a bug in the latest version of Photoshop (23.21)? If so, is there some workaround for this issue?

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Community Beginner ,
Mar 07, 2022 Mar 07, 2022

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@Creative23439658gw6x I had that issue too, going to Preferences > Export and checking Use legacy "Export As" at the bottom worked as a workaround for me for now.

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Adobe Employee ,
Mar 07, 2022 Mar 07, 2022

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@Serena... and @Creative23439658gw6x To summarize the matter, we fixed an issue where selecting the Smaller File (8-bit) option was not creating smaller 8-bit files. If you are happy with the results from before the fix or with what you get when switching back to the Legacy version, then simply do not turn on the Smaller File (8-bit) option in the latest update to get the same results. 

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Community Beginner ,
Mar 07, 2022 Mar 07, 2022

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@BrettN That's great that you fixed it, but I never had any problem before with smaller 8-bit files being created, they were always smaller than the PNG-24 option and therefore there was no issue. So to some people, rather than fixing anything, you just changed the way it worked where it now works worse than it did before, creating low quality images that are actually larger than the PNG-8s being made with legacy options enabled.

I just did several tests and every time the new PNG-8 export was larger than the legacy one, 248 vs 238 kb, 7.5 vs 6.5 kb, etc, with the smaller numbers being the result of using legacy export. 

It's great that the legacy option is there for us to use, but what about when you phase it out, are we just stuck never being able to export a smaller PNG with partial transparency? The fact that your PNG-8 system now doesn't support the partial transparency is ridiculous considering that's one of the main features of PNGs. If you look at the W3 standard for PNGs, 8 bit supports alpha transparency, so there's no real argument on why to exclude it.

(You also mention not choosing the 8 bit option if we do not like how it looks now, but for web developers that simply is not an alternative that can be done. The file size difference in a 24 bit photo to an 8 bit photo is dramatic, and files used on websites need to be as small as possible without sacrificing too much quality, which is now impossible on PNGs with your current system only exporting 8 bit images with jagged edges and no partial transparency.)
Is there really no way you can come to a middle ground, and either fix it again so that the PNGs actually have one of their basic functionalities, or give us an option in the new export as dialouge to chose if there's partial transparency in it or not? PNG-8 could be a separate option from 'smaller' PNG-8 for example, if the jagged-edged no partial transparency data option is truely smaller. 

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Adobe Employee ,
Mar 07, 2022 Mar 07, 2022

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Unfortunately, the naming of this option is doubly confusting. First, "Smaller File" makes it sound like it is "optimized" or more compressed. But it is really just trying to describe a complext topic, as described below, in a simple fashion. Second, "(8-bit)" does not mean 8-bits per channel, like a JPG. It means 8 total bits to describe all colors (256 total) in an indexed color table, like a GIF. I'm hoping to get the language updated in the future so that it is more clear what this option is actually supposed to do. 

 

This bug was the equivalent of choosing to export as GIF and ending up with a JPG. That is pretty major. But it only happens when the project contains semi-transprent pixels, so not everyone would run into it. Also, due to the naming of the option, some weren't aware of what the outcome of this option was supposed to be. 

 

PNG files come in three bit related flavors: 32-bit, 24-bit, and 8-bit. These are not the same as the 32-bit, 16-bit, and 8-bit options that we normally think of in Photoshop. Instead of bits per channel, these are the sum of bits across all channels. To get a 32-bit file (four 8-bit channels: R, G, B, and Alpha) in Export As, you turn on "Transparency" and turn off "Smaller File (8-bit)". To get a 24-bit file (3 8-bit channels: R, G, and B), turn off both options. And to get an 8-bit file (Index color), turn on "Smaller File (8-bit)". An 8-bit file will be smaller than a 32-bit or 24-bit file simply due to the reduced number of channels, hence the option name.

 

8-bit Index files do not support semi-transprent pixels. The color table can only have a single, fully transparent pixel registered. It takes an Alpha channel to have a full range of partial opacity. And only an RGB PNG file supports Alpha (AKA a 32-bit PNG).

 

There are currently five ways to create PNGs in Photoshop and each will result in different file sizes from the same project file. The methods are: Save As, [UXP] Export As, [CEP] Export As (Legacy), Generator, and Save for Web (Legacy). Save As only produces 32-bit PNG files. Generator and CEP Export As both create 32-bit PNG files when exporting semi-transparent pixels (CEP Export As is basically just a UI for Generator). Save for Web is the original option for creating 24-bit and 8-bit PNG files. Both UXP Export As (with the update) and Save for Web correctly export Index 8-bit PNG files. The big difference between these two is that Save for Web has a matte option, which helps to anti-alias the semi-transparent areas to make things appear smooth. I'm hoping we can get that added to UXP Export As in the future as well. 

 

If you are simply looking for the option that will give you the smallest 32-bit PNG file, then Generator is what you want to use. Just add ".png8" to your layer (or layer group) name and turn on File > Generate > Image Assets. This is still a bug, but it will give you even smaller files than using Export As (Legacy) or any of the other options.

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Adobe Community Professional ,
Mar 07, 2022 Mar 07, 2022

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Sounds like some users were expecting Export As>PNG with Smaller file (8 bit) to have Semi-transparency like Adobe Fireworks can do with 8 bit pngs .

 

https://feedback-readonly.photoshop.com/conversations/default_topic/photoshop-support-png8-with-alph...

 

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