How to change the size of image in splash screen?

I had the same issue but here is what I did.

I changed the "center" value to "fill"

that is

<item>    <bitmap android:gravity="fill" android:src="@drawable/splash" /></item>

Simple: create bigger logo files

I was also having the same problem, because my logo as you can in this print below, was very small:

Why?

Why the files that were in the "hdpi", "mdpi", "xhdpi", "xxhdpi", "xxxhdpi" folders respectively were in pixel sizes: 48, 72, 96, 144, 192, 512

How to fix?

Create bigger logo files

In my case, I doubled the pixel size of the files in the folders I mentioned above, so the "hdpi", "mdpi", "xhdpi", "xxhdpi", "xxxhdpi" folders were respectively pixel sizes: 88, 144, 192, 288, 384, 1024. And the result was this:

It seems to be possible in Android starting from API 23 by doing something like this:

    <item        android:gravity="center"        android:drawable="@drawable/logo_splash"        android:width="100dp"        android:height="100dp">

But I don't know how this will play with different resolutions and screens.

If you know a package or a way to solve it on Android and IOS it will be perfect. :)

There is a plugin that seems to do what you are looking for without the needs for you to configure both IOS & Android, please take a look at https://github.com/henriquearthur/flutter_native_splash

EDIT: Assuming from your question you are talking about a native splash screen, not just the initial page of your app.