Paint.net compresses my files and makes them useless

[Arbu]

I've got a 50kb png file which someone else has created for me. I open it with paint.net then save it as a new file. This file is only 1KB. If I try to show it on my website it looks all wrong, unsurprisingly. See the image below - the top image is the original the bottom one has been through Paint.net. 

 

What's going on and how do I stop this? I tried letting Paint.net auto select the bit depth, and selecting 32bit myself but it made no difference.

 

I can't use MS Paint because I need an area of invisible colour.

 

Thanks

[Arbu]

OK, sorry, the problem is with how I'm setting the image sizes on my website, not Paint.net. Surprising that it reduces the file sizes so much.

 

Here's a before and after. They are both pngs. The first is 47.93kb. The second I have created by opening the first with Paint.net and saving it at 32 bits. It is only 727b. 

Edited May 23, 2017 by Arbu

[Zagna]

Your original image has only 616 bytes of actual image data and large amount of data in other bits. 12kB in xml text and 35kB in ancillary chunks.

The version made by paint.net has 583 bytes of image data and discards all the proprietary chunks.

So there's actually only a 5% compression from Fireworks CS6 to paint.net.

Edited May 23, 2017 by Zagna

[Rick Brewster]

If you want to minimize files size then you should always use a "post-processing" solution, like PNGGauntlet or pngcrush or whatever the hot new thing is these days.

 

Paint.NET doesn't have "crusher" functionality built-in to its PNG codec because it's REALLY REALLY SLOW. Like 30 seconds to save a 50KiB image. You don't want that every time you press Ctrl+S. Just do it once, when you're done, before you upload.