User's Guide

MULTIPLY

Compute the pixel-by-pixel product of up to ten input images

Function:

Performs pixel-by-pixel multiplication on a set of up to ten input images (single or multi-band) to form a single output image. Each output pixel is the product of all the input pixels at the same position. At the user's option, the input data may be interpreted as complex numbers. In this case, a complex multiplication is performed on pairs of values with the first half of the pair being interpreted as the real part and the second half as the imaginary part of the complex number.

Parameters:

IN

Input images. Specifies the input images to be processed. Two to ten images may be given as input. Window and/or band options may be specified. The images may be multi-band, but each input must have the same number of bands. Any combination of BYTE, INTEGER*2, INTEGER*4, or REAL*4 data types are accepted. Image sizes may differ although the minimum intersection is computed based on all inputs.

OUT

Output image. Specifies the name of the output image. It will have the same number of bands as the input images. The minimum intersection of all input images will determine the size of the output image. If MULTOPT = COMP, the size of the output image will be one-half the number of pixels of the minimum intersection of the inputs. The output data type is set by the parameter ODTYPE. .

MULTOPT(STD)

Multiplication option. Specifies the type of multiplication to be performed.

  = STD:   Standard multiply.  A simple arithmetic 
           product is formed from the input images.
  = COMP:  Complex multiply.  A complex arithmetic
           product is formed from the input images. 
           The output data type will be REAL*4, and 
           the size of the output image will be 
           one-half the number of pixels of the minimum 
           intersection of the input images.  Complex
           multiplication may be requested for any 
           input data type; however, the number of 
           input pixels must be even.

ODTYPE("BYTE")

Output data type. The data type of the output image.

  = SAME:  Same as input
  = BYTE:  BYTE      (8-bit unsigned integer)
                     (0 through 255)
  = I*2:   INTEGER*2 (16-bit signed integer)
                     (-32768 through 32767)
  = I*4:   INTEGER*4 (32-bit signed integer)
                     (-2147483648 through 2147483647)
  = R*4:   REAL*4    (32-bit signed real)
                     (System dependent)

Examples:

1. LAS> multiply in=(first.img, second.img) out=res.img

   Pixel-by-pixel multiplication is performed, and the result is stored in the RES.IMG.

2. LAS> multiply in=(one.img, two.img, three.img) out=res2.img multopt=comp

   Complex multiplication is performed on the three input images. The output data type will be REAL*4.

Description/Algorithm:

For n input images, n-1 multiplications are performed to generate each output pixel. Each of these is either a standard multiplication or a complex multiplication involving pairs of values: (a+bi)(c+di) = (ac-bd) (ad+bc)i.

Nonfatal Error Messages:

None.

Fatal Error Message:

1. [multiply-nbands] All images must have the same number of bands

   There is a mismatch in the number of bands. Respecify the images with equal number of bands.

2. [multiply-evenpix] Number of input pixels must be even for complex multiply

   Complex values are represented by pairs of values. The input images must be windowed so that the number of pixels is even.

User Notes:

1. When MULTOPT = COMP and the user specifies a window, the pixels refer to complex pixels, i.e., to pairs of values.