Sometimes we want to do remote sensing mapping, but we use normal addition and subtraction. In the end, only the part where the two images intersect is obtained. Let's look at the function first:
subtract(image2)
Subtracts the second value from the first for each matched pair of bands in image1 and image2. If either image1 or image2 has only 1 band, then it is used against all the bands in the other image. If the images have the same number of bands, but not the same names, they're used pairwise in the natural order. The output bands are named for the longer of the two inputs, or if they're equal in length, in image1's order. The type of the output pixels is the union of the input types.
Subtract the first value from the second value for each pair of matched bands in image 1 and image 2. If image 1 or image 2 has only 1 band, then it will be used against all bands in the other image. If images have the same number of bands but different names, they are used in pairs in their natural order. The output tapes are named after the longer of the two inputs, or in the order of image 1 if they are of equal length. The type of the output pixel is a union of the input types.
Arguments:
this:image1 (Image):
The image from which the left operand bands are taken.
image2 (Image):
Th