The purpose of the crop node is to create a physically smaller size texture and not to create "black" or “transparent” blanking for the outside of the pixels. When a texture is being cropped, its size is getting smaller. Textures are always being used as full screen (Fill mode) by default, in other words, it's “crop and fill”. The cropped edge always fills the texture from every corner.
Working with Crop Node
CROP node is available under the "Process" category.
Each side can be cropped independently with different values ranging from 0.000 to 1.000. i.e. 0% to 100%.
0.000 is equal to 0% and 1.000 is equal to 100%. In the above image, LEFT property is cropped with 20%.
In the example below, we have cropped from all 4 corners. All 4 corners are cropped proportionately to maintain the original aspect ratio of the texture and then the texture is resized to fill the screen.
Proportionately cropped texture to maintain aspect ratio.