Among them, png images support their own transparent channels, so this is for convenience.
However, it is recommended to set the mask image here.
The size of the mask image corresponds to the original image. The pure black part is a completely transparent area of the original image, the white part is a completely opaque area, and the gray part is translucent according to the depth of the color scale.
The original image is named xxx_m.png, so the corresponding mask image is named XXX _ m.png. If it is placed in the same folder, it can be automatically read in. Masked images are not only effective, but also convenient to modify when local translucency of the image is needed, or the edges drawn vertically are smooth.