Identifies the type of arithmetic operation (merge method) that is performed on the values of all intersecting pixels resulting from the merge.
For example, if you set IG_ARITH_ADD merge method, the resulting pixel values (of those pixels that intersected from the two images) equal the sum of the value of the pixel in the original image and the value of pixel in the image being merged.
| IG_ARITH_ADD | Img1 = Img1 + Img2 |
| IG_ARITH_ADD_SIGN_CENTERED | Img1 = Img1+ SC_Img2 |
| IG_ARITH_AND | Img1 = Img1 & Img2 |
| IG_ARITH_DIVIDE | Img1 = Img1 / Img2 |
| IG_ARITH_MULTI | Img1 = Img1 * Img2 |
| IG_ARITH_NOT | Img1 = ~Img1 |
| IG_ARITH_OR | Img1 = Img1 | Img2 |
| IG_ARITH_OVER | Img1 = Img2 |
| IG_ARITH_SUB | Img1 = Img1 - Img2 |
| IG_ARITH_XOR | Img1 = Img1 ^ Img2 |