I think it reduces file size by using indexed colors -- basically transparent GIF compression.
For the web, it would probably save time and bandwidth.

Check for visible banding in blue skies -- that will indicate it's usefulness for your purposes.
I guess the idea of lossy PNG compression tastes like strange salad to me; like John_Dennis, I'll stick with Irfanview

Yes, TinyPNG is worth it for what you are doing Spectralis.
I highly recommend grabbing a copy, it's also what i use.

Thanks for the feedback. Is it possible to batch convert file size with either TinyPNG or Irfanview? Does Irfanview retain transparency when reducing file size and will these files still work with Vegas? I can test this myself but thought I'd get some tips from more experienced users. Steve do you notice much reduction in image quality when reducing PNG's with TinyPNG? How much file size reduction is possible before the image quality is compromised?

IrfanView's PNG compression levels are lossless.

With IrfanView you can choose from several batch conversion options, just like resizing, rotate, sharpen, color correction and some more.

IrfanView retains transparency for PNG, no matter which compression level selected and the converted files will work fine in Vegas Pro.

At least all that worked for me in the past.

Marco,

+1

Though retaining transparency by IrfanView's PNG output has some limitations, e.g. if you export a text with shadow on transparent background from Vegas Pro as PNG, import this one into IrfanView and output again, you will get your text on transparent background but the shadow will be gone.
Not sure if there is a way to optimize this in IrfanView by using the PNGOut plug-in.

No, there is no visible reduction in image quality using TinyPNG
and far superior than Irfanview in every way, including the fact that
it is a plugin.

Steve Rhoden,
Saying that you prefer one utility over another is something a reader can respect.

Just leave it at that though.

I don't plan on trading in lossless PNG compression for indexed color any time soon, and if I did, why wouldn't I still be using GIF?

Sorry, i dont leave issues just like that musicvid10.
And i did not say i prefer one utility over another.... I made it clear that
TinyPNG is better.

But I thought PNG was invented to replace indexed color, rather than use it?
http://www.sonycreativesoftware.com/forums/showmessage.asp?forumid=4&messageid=941627

Actlually, Marco knows more about this stuff than I do . . .

This surprised me, either.

I tested the TinyPNG web client (no glue how to use it as plug-in besides in Photoshop) and the resulting file size was bigger than the IrfanView output. But the TinyPNG output did a better job processing the alpha channel (it preserved shadows).

I just tested the free command line version of PNGOUT which is also available in various GUI versions. This tool is slow but lossless and it also preserves all alpha channel information, so in terms of alpha processing it's better than IrfanView while in terms of quality it is better than TinyPNG - for the cost of speed.

Marco,
PNGOUT plugin is the only thing I use in Irfanview.
Do you get the shadow problem using that?

From what I read the transparency problem is caused already by IrfanView reading the incoming PNG file. It seems like it just doesn't read the alpha channel. It doesn't matter if you use the PNGOUT plug-in then because all you can do (with or without PNGOUT plug-in) is defining a color which will represent transparency for the resulting PNG file. In IrfanView I tested with and without PNGOUT plug-in. No difference.

I saw many IrfanView users complained about that issue and actually it was set onto a to-do list many years ago (2007?) but never found its way into IrfanView, so doubt it will ever happen.

But PNGOUT itself (not the plug-in) does a good job (except of its slowness). Even with the command line version you can batch convert whole directories. I did not yet get all the various options. Maybe there is a way to speed up the tool by reducing its process cycles.

Thanks for the info, that helps.
I probably haven't tried text shadow on transparent background, but I've got some images like that to try.

After testing TinyPNG, it reduces the file size significantly without noticeable loss of image quality as advertised. I've gone for the TinyPNG plugin because I prefer faster batch processing even if this means a slight loss of image quality due to compression. A 5 min animation at 24fps has thousands of PNG files. Multiply that when compositing different animation layers and I'd rather sacrifice a bit of image quality for batch processing speed. If there was a way to batch process faster using PNGOUT then that lossless method would be preferable.

I think in your case any tool which relies on core PNG lossless features like PNGOUT won't fit your needs. Even with best optimizing in these cases you won't save any more than maybe 5 or 10 percent of data, compared to the PNG output out of Vegas Pro. Maybe even less than 3 percent. And I think that's what you aim for - data reduction of Vegas exported PNG files.
I found ways to speed up PNGOUT and this result in slightly bigger files - which would reduce the saving even more.

So for my own purpose PNGOUT seems to be great but it wont't be good for you. Vice versa TinyPNG isn't my choice as - besides of its color palette reduction - I don't use Photoshop.

Thanks everyone for your feedback. I went for TinyPNG but will keep an eye out for a free app that does lossless PNG reduction and fast batch processing if one appears in the future.

Spectralis, TinyPNG works by reducing the number of colors in the image. It is designed to reduce PNG images meant for web display. It is not meant for saving frames of a video.

IrfanView is great, but if your PNG contains the alpha channel, chances are IrfanView will mess it up.

For our purposes, as video editors, pngcrush is probably your best bet. It is a command line utility, so you would use it like this:

pngcrush -l9 input.png output.png

The -l9 (that is a lower-case L, not an upper-case i) tells it to use use maximum compression. It will read input.png, try 10 different compression methods, pick the one that compresses the file the most, and write output.png. It will do so in a lossless manner, so, unlike TinyPNG, it will not reduce the number of colors in the image.

You can download the current executables for Windows from this link, where you can choose the 64-bit or 32-bit version. Of course, you presumably have 64-bit Windows, so I would go for the 64-bit version. Its name is pngcrush_1_8.1_w64.exe, but once you have downloaded it, you can rename it to just pngcrush.exe (or anything you want).

Adam