Image file size changes after import.

vafurlogi

I've been working on a game for a long time now. The game has a lot of images so I used 8bit 72DPI with transparency where I could to save on game size (not memory). I was messing about in the project file and comparing images before and after I imported them in to the project. File sizes are vastly different.

The first image was a 1024x680 px - 8bit with transparency and 72 DPI made with photoshop. Both the original image and the imported image have the same specs and look identical. It's still 8 bit and 72 DPI after import. Before importing the file size is 61 kb. After import the image is 240 kb. For almost 600 images this adds up fast.This is also true for 16bit PNG files but the difference is a lot less, something like 116 kb vs 140 kb.

Now, I then just replaced the imported image with the original PNG file. It works and looks identical but saves me almost 4x the file size. Does anyone know why this is and if there's a problem in doing this? I might be missing something simple here.