binary mask

• Mask (computing) - wikipedia 掩码，多位操作
• Bitmap - wikipedia 一种映射关系
• Nibble - wikipedia 表示 4 bits

Mask

In computer science, a mask is data that is used for bitwise operations（按位操作）, particularly in a bit field.
Using a mask, multiple bits in a byte, nibble, word etc. can be set either on, off or inverted from on to off (or vice versa) in a single bitwise operation.（采用mask，可以实现多位 置0或1，即 on, off）

Image mask

In computer graphics, when a given image is intended to be placed over a background, the transparent areas can be specified through a binary mask.

中间的图 就是 image mask

Bitmap

In computing, a bitmap is a mapping from some domain (for example, a range of integers) to bits (values which are zeros and ones). It is also called a bit array or bitmap index.
举例：把一些实数 映射到（map）二进制（0, 1）形成一个位数组（只由 0 1 组成的数组）

In computer graphics, when the domain is a rectangle (indexed by two coordinates) a bitmap gives a way to store a binary image, that is, an image in which each pixel is either black or white (or any two colors).
bitmap 可以把 一张 图片 转成 只由 黑白 两色组成

• 点阵图（BMP 位图，Ps）
• 矢量图（Illustrator，CorelDraw）