Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download Alpha Mask: UI, Sprites, Tilemaps, Particles, 3D Free.
Alpha Mask v2.1
Alpha Mask v1.51
Works with Unity 5, Unity 2017 and Unity 2018.
Alpha Mask is a simple component used for alpha masking, similar to Flash or Photoshop.
– Works with Unity UI (uGUI) Images and Text, Sprites, Tilemaps, Particle Systems and 3D Transparent Unlit objects.
– Supports any shader (including TextMesh Pro) by simply copying a few lines of code (thoroughly described in the documentation)!
– Supports mobile, PC and all other platforms.
– Soft, anti-aliased, gradient and semi transparent masks supported.
– All script and shader sources included!
– Extremely easy to use.
– Mask textures can be clamped horizontally/vertically.
– Easy mask positioning in the Editor.
– Supports mask moving, scaling, rotation, UV scaling, UV offset.
– Fully supports RectTransform anchors, pivots etc. for the Mask and the masked elements.
– Supports all Canvas render modes: Screen and World Space.
– Masks can be freely rotated and mapped on any direction.
– Can be used for UI or 2D games (including either Unity UI, Sprites, Tilemaps, Particle Systems or 3D Quads).
– A sample with multiple alpha masks on a single sprite included (using a RenderTexture).
Ask questions or discuss the plugin here.