RenderTexture memory size when converted to PNG

I'm using unity to capture 128x128 png images from the scene. What I noticed is that the captured images are having different sizes. Some of them are too small while others are too large.

From my understanding that png images are affected by the resolution, am I missing something here? why are the sizes vary? is there a way to make it the same?

 

What do you mean by size? First you said they are all 128x128, then you said they have different sizes. Which is it?

 

Sorry if that wasn't clear, I mean their size in memory when exported using EncodeToPNG. (in bytes)

 

PNG data sizes will vary because PNG is a compressed image format. Depending on the characteristics of the image, that compression will be more or less effective, resulting in more or less space savings, e.g. different file sizes.

 

Thanks!!

is there a way to avoid it? like by encoding to different format?

 

Sure, you could use https://docs.unity3d.com/ScriptReference/ImageConversion.EncodeToTGA.html

 

Thank you very much.