Removing Image Button Padding (Android)

You cannot do that with the default buttons, the buttons 9 patches have a padding in them (both, holo and the pre holo buttons). You can see that here.

If you want buttons without padding then you'll have to modify the 9 patches and create your own theme:

<style name="myTheme" parent="....">
    <item name="imageButtonStyle">@style/myImageButton</item>
</style>

and your imageButtonStyle:

<style name="myImageButton" parent="Widget.ImageButton">
    <item name="android:background">@drawable/myCostomizedNinePatchSelectorWithoutPadding</item>
</style>