The image is a square that is made up of a lot of little squares. Some of the squares are darkened and other are not. Along the outer edge of the bigger square, some of the squares are opened on one side.
This is a Opacity icon. We've made it in iOS style
, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 13,900 icons, all in the same style and quality.