Weird. I just noticed a simple white frame saved as a PNG being almost 8 MB. So I opened Photoshop (CS6) and saved it again (save as, replace). Now it is 806 KB. Did the same thing with a piece of paint (24 MB - now 7,8 MB) and also some tinier stuff like brads (450 KB - now 168 KB).
Why? Am I saving my PNG files the 'wrong' way in the first place? Is there a way to get the files to save smaller right away or should I just save them twice always to make them smaller? Or have I just done something to make them lose quality? That is not supposed to happen to PNG files, right?
Does anybody have answers? I would love to know!
If you save a PNG as interlaced it becomes a smaller file and ready for the internet. It also does not have the same quality.
For PNG you have an option to save interlaced or not. To save for the best picture you won't want to save interlaced.
Thanks for the explanation, Judy!
You are welcome.
That's the thing Judy: I'm not saving as interlaced - since I'm a webdesigner by day, I know what the interlaced feature means, so I keep away from that when saving for print. No, I save exactly the same way, only the second time the file is a lot smaller. I haven't tried saving for a third time...
PNG unlike jpg does not lose any of its quality each time you resave. Could the resave be changing the bit rate to something lower, which would reduce the size?
PNG's compression is fully lossless and can support up to 48 bit truecolor. Do you see any change in the quality of the object?
You may want to consider editing the original Photoshop format and resaving as PNG to make sure that the image is not degraded.
I can't see any changes in the file itself, no quality loss, only the smaller file-size. If I go back to Photoshop and resave, it is the same (big) size again, but I don't see any difference with the snaller size one.
The only thing I can think of is that Photoshop is compressing it more, which would result in a smaller file size.
Some other things to check, did your dpi change between saves?
Are you using the Save as.. dialog to save the png or the 'save for web' dialog?
There is a known problem of sorts in CS6 where it does not save all the metadata it is suppose to in a png. This could explain why you are not seeing any quality loss since the "fat" that was trimmed from the file size isn't visible but if you are only saving and then resaving in PS then there shouldn't be any metadata for it to trim. Are you maybe opening it in another program that might be adding metadata?
I've gotten away from PS for pngs. I was noticing quality loss in my pngs in Photoshop no matter how I saved them. I use Illustrator almost exclusively for anything I want to save as a png any more. There are a lot more saving options for png and no loss of quality that I can notice. A lot of web designers are getting away from PS for the same reason. Lack of png optimization options without using plugins and out dated transparency algorithms being the most often cited reasons.
https://forums.adobe.com/thread/1264084
https://www.smashingmagazine.com/2009/07/clever-png-optimization-techniques/
It's an old topic but I might have an answer for it
I assume when you first saved your image (the very first time) it had textures, or styles, or maybe it was a smart object.. Photoshop, might have treat it as if you are saving it as a layered file and therefore file size increased when you first hit save. However when you opened it, it was now a flat png file without any style, texture or whatsoever. And that decreased the actual size of the file. So it's a glitch in Photoshop.
It also does happen when you give a layer a long name and save it like that.
When I've reviewed my old designs like papers for instance I see that they has huge file sizes. And only in the past year I was able to understand what's going on, why my never designs are less smaller in mb. And that was because I was saving my files without flattening them, with all the textures and layers, sometimes there were layers included in the file that are bigger than the actual file size and they were out of canvas so I wasn't seeing them at all. As I mentioned above, then the Photoshop treats the file as if it's layered. So, what I do now instead is deleting all the unnecessary layers, flattening or merging the layers, making sure that no any pixel remains out of the canvas and then I save it. In recent years my design files are very small that even I am shocked! My 12inch size (300dpi) papers are now raging from 800kb to 4 mb according the complexity of colors. And an average elements kit of mine including 35-60 png elements are ranging from 5mb to 15mb (but mostly under 10mb). That's a huge storage saving
Ha! That must be it Elif! I always save without flattening the file, so that certainly explains why the files are huge to start with. I wiil try flattening before saving from now on. Thanks!
I realize this is a somewhat older posting and you most likely already know this but if your expected end result is to have a PNG with transparency, then you do not want to "flatten" the file; instead you should "merge" the layers, flattening will cause the transparent areas to be filled with white.