# Masking with Bitwise Operation

## Bitwise Operation

`bitwise_and(), bitwise_not()` and more

Computes bitwise conjunction of the two arrays (src1, src2) and calculates the **per-element bit-wise** conjunction of two arrays or an array and a scalar.

### bitwise\_and()

| void cv::bitwise\_and | ( | [InputArray](https://docs.opencv.org/4.x/dc/d84/group__core__basic.html#ga353a9de602fe76c709e12074a6f362ba)  | *src1*,                                                                                                                 |
| --------------------- | - | ------------------------------------------------------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------- |
|                       |   | [InputArray](https://docs.opencv.org/4.x/dc/d84/group__core__basic.html#ga353a9de602fe76c709e12074a6f362ba)  | *src2*,                                                                                                                 |
|                       |   | [OutputArray](https://docs.opencv.org/4.x/dc/d84/group__core__basic.html#gaad17fda1d0f0d1ee069aebb1df2913c0) | *dst*,                                                                                                                  |
|                       |   | [InputArray](https://docs.opencv.org/4.x/dc/d84/group__core__basic.html#ga353a9de602fe76c709e12074a6f362ba)  | *mask* = [`noArray`](https://docs.opencv.org/4.x/dc/d84/group__core__basic.html#gad9287b23bba2fed753b36ef561ae7346)`()` |
|                       | ) |                                                                                                              |                                                                                                                         |

{% embed url="<https://docs.opencv.org/4.x/d2/de8/group__core__array.html#ga60b4d04b251ba5eb1392c34425497e14>" %}

### Example

`bitwise_and(src1,src1,dst1, mask1)`

This means dst1(I)= src1(I) & src1(I), if mask(I) !=0

Assume src\[10]\[20] = 1111 0001 / / 8-bit data per pixel

### Case 1

Since binary logic AND is **X & X=X**

1111 0001 & 1111 0001 = 1111 0001

The output of bitwise operation becomes

dst=src & src = src

### Case 2

Since binary logic AND is **X & 1=X**

1111 0001 & 1111 1111 = 1111 0001

The output of bitwise operation becomes

dst=src & 1 = src

### Case 3

Since binary logic AND is **X & 0=0**

1111 0001 & 0000 0000 = 0000 0000

The output of bitwise operation becomes all black.

## Masking and Merging

<figure><img src="https://3883264845-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MR8tEAjhiC8uN1kHR2J%2Fuploads%2FXxoXDUsNy3NWzB7sa6Sp%2Fimage.png?alt=media&#x26;token=adf0721c-f886-461f-bf7f-f82cc017a1e8" alt=""><figcaption></figcaption></figure>

dst1 and dst2 can be obtained using bitwise operation as

For both 1-CH and 3-CH images

```cpp
bitwise_and(src1, src1, dst1, mask1);
bitwise_and(src2, src2, dst2, mask2);
dst3=dst1+dst2;
```

Also, you can apply as

```cpp
dst1=src1 & mask1;         // This is NOT the same as  && operation 
dst2=src2 & mask2;
dst3=dst1 + dst2;
```