Calculates the per-element difference between two arrays or array and a scalar

dst = cv.subtract(src1, src2)
dst = cv.subtract(src1, src2, 'OptionName',optionValue, ...)

Input

• src1 first input array or a scalar.
• src2 second input array or a scalar.

Output

• dst output array of the same size and number of channels as the input array(s). The depth is defined by DType or that of src1/src2.

Options

• Mask optional operation mask; this is an 8-bit single channel array that specifies elements of the output array to be changed. Not set by default.
• Dest Used to initialize the output dst when a mask is used. Not set by default.
• DType optional depth of the output array: uint8, int16, double, etc. (see the discussion below). Must be specified if input arrays are of different types. default -1

The function cv.subtract calculates:

• Difference between two arrays, when both input arrays have the same size and the same number of channels:

  dst(I) = saturate(src1(I) - src2(I)) if mask(I) != 0
  

• Difference between an array and a scalar, when src2 is constructed from Scalar or has the same number of elements as size(src1,3):

  dst(I) = saturate(src1(I) - src2) if mask(I) != 0
  

• Difference between a scalar and an array, when src1 is constructed from Scalar or has the same number of elements as size(src2,3):

  dst(I) = saturate(src1 - src2(I)) if mask(I) != 0
  

• The reverse difference between a scalar and an array in the case of SubRS:

  dst(I) = saturate(src2 - src1(I)) if mask(I) != 0
  

where I is a multi-dimensional index of array elements. In case of multi-channel arrays, each channel is processed independently.

The first function in the list above can be replaced with matrix expressions:

dst = src1 - src2;

The input arrays and the output array can all have the same or different depths. For example, you can subtract to 8-bit unsigned arrays and store the difference in a 16-bit signed array. Depth of the output array is determined by DType parameter. In the second and third cases above, as well as in the first case, when class(src1) == class(src2), DType can be set to the default -1. In this case the output array will have the same depth as the input array, be it src1, src2 or both.

Note: Saturation is not applied when the output array has the depth int32. You may even get result of an incorrect sign in the case of overflow.