Every digital ad that I produce has pngs that have been processed through ImageAlpha. I can’t stress enough how invaluable that tool is to my workflow.
It hasn’t been updated for quite some time though. Now that I’m running it on Monterey, the OS pops up a message that ImageAlpha won’t work when the next Apple OS version drops.
Is there another GUI app similar to ImageAlpha? I’m hitting dead ends.
This comparison page does show some alternatives. I personally use ImageOptim, but it doesn't seem to have the same preview UI and I just use blind. I know Photoshop's Save for Web stuff lets you configure PNGs a bit, but I don't know how well it compares.
I use ImageOptim regularly for JPGs but I haven't found that it decreases PNG sizes much. Kraken looks promising, though. I haven't come across that before. Thanks, @jonathan!
Recently, I've started to use Sqoosh for this kind of task. This site is also particularly useful for converting to new formats like WebP.
A reminder to everybody: ImageAlpha and ImageOptim are Open-Source and maintained by the great Image compression tinkerer ⇨ https://twitter.com/kornelski
If these tools have made your life easier and or helped you finish a job and meet its restriction … in present day or in the past: Show the author and maintainer some love and support him with a …
ImageOptim is maintained, sadly ImageAlpha is not. Been about 4 years since that one has been touched. But yes, def show him some love!
I just grabbed 2 transparent PNGs I used in a recent ad. One is silo-ed photographic elements, the other is 2-color text (as image). Here's what I got:
photo.png
139 KB - original image
109 KB - ImageOptim
36 KB - Kraken
32 KB - Squoosh
29 KB - ImageAlpha
text.png
21 KB - original image
16 KB - Kraken
14 KB - ImageOptim
14 KB - Squoosh
6 KB - ImageAlpha
ImageAlpha for the win in both cases. Squoosh is super fast and allows tinkering, so that's 2nd place winner. Of note, ImageOptim took a good 20 seconds to spit each of these out.
My current plan is to maintain a machine with Mojave OS just to process image files through ImageAlpha. 
Thanks for those benchmarks!
ImageOptim does tend to take quite a while as it seems to run through various ways to try to reduce the size. Note that he default settings don't use any lossy compression for PNG, so if the others are doing that it will definitely affect the results quite a bit. It looks like ImageAlpha is lossy by default. Personally I keep all my PNGs lossless and just use JPEG if I want something lossy, but I guess this may depend on your usage of alpha transparency in the image. It also seems like PNGCrush isn't enabled by default, but I'm less clear on the tradeoffs there.
(Not that I'm arguing on behalf of it, just it is the one I happen to use and am more familiar with)
I've never looked at the ImageOptim prefs, but I'll have to do that now. My little test was not very scientific, I just wanted to identify what might have potential for me.
Yeah, I spoke to the developer of ImageAlpha. He considers the project "dead" as it was written in Python 2. He is leaving it up there for now and as long as the OS supports it your computer should be able to run it. Furthermore, he suggests using Squoosh going forward. I like the two main contributor surma and jakearchibald of Squoosh (and their YouTube show will be dearly missed), I don't like that it isn't native.
Impressive compression, @intaplink! Here's the updated line-up using my 2 pngs:
photo.png
139 KB - original image
109 KB - ImageOptim
36 KB - kraken.io
32 KB - squoosh.app
32 KB - iloveimg.com
29 KB - ImageAlpha
text.png
21 KB - original image
16 KB - kraken.io
14 KB - ImageOptim
14 KB - squoosh.app
7 KB - iloveimg.com
6 KB - ImageAlpha
maybe upper ways are freeware...but I'm using tiny jpg or tiny png which works by browser of photoshop plugins...
and I've tested it on iloveimg.com, but
tiny jpg/tiny png..wins this in lower kb's
there is a other way...thanks to MaxZ...It works...but it cost some extra energy
https://forums.tumult.com/t/aw-hype-compressor/20460
I can't tell from tinypng.com's site if their plugin compresses any more than the web interface. I'm guessing it would be the same, but their plugin isn't M1 processor compatible yet, so I can't try it.
Using the Tiny Png web interface, my files come in at 34KB and 9KB for photo.png and text.png respectively. Not quite as small as I Love Img, ImageAlpha in this particular case. What helps give ImageAlpha an edge is that I can manually reduce the number of colors.
I appreciate the options!