NAME

mkpattern - Make/add patterns in images

USAGE

mkpattern input

PARAMETERS

input

Images to create or modify. Image sections are allowed to apply a pattern to a portion of an image.

output = ""

Output images when modifying input images. If no output images are given then existing images in the input list are modified directly. If an output image list is given then it must match in number the input list.

pattern = "constant"

Pattern to be used. The patterns are:

constant

Constant value v1.

grid

A grid starting with the first pixel and going in steps of the pattern size with value v2. Pixels between the grid have value v1. A minimum grid size of 2 is enforced.

checker

A checkerboard with squares of the pattern size alternating between values v1 and v2 starting with v1.

coordinates

Each pixel is numbered sequentially starting with 1 with the column dimension varying fastest.

slope

A sloped plane starting with value v1 for the first pixel and value v2 for the last pixel in one or two dimensions.

square

A checkerboard pattern in which the size of the squares begin with the pattern size and grow as the square of the coordinate.

option = "replace"

Editing option when modifying existing images. Often this is used in conjunction with image sections to modify a part of an image. The options are:

 replace - Replace the image with the pattern.
     add - Add the pattern to the image.
multiply - Multiply the pattern with the image values.

v= 0., v2 = 1.

Pattern values used as described for each pattern.

size = 1

Pattern size used as described for each pattern.

WHEN CREATING NEW IMAGES

title = ""

Image title to be given to the images. Maximum of 79 characters.

pixtype = "real"

Pixel datatype of new images; one of ushort, short, integer, real, double, or complex.

ndim = 2

Number of dimensions between 0 and 7.

ncols = 512, nlines = 512

Number of columns (first dimension) and lines (second dimension).

n= 1, n4 = 1, n5 = 1, n6 = 1, n7 = 1

Number of pixels in 3rd-7th dimensions

header = "artdata$stdheader.dat"

Image or header keyword data file. If an image is given then the image header is copied. If a file is given then the FITS format cards are copied. This only applies to new images. The data file consists of lines in FITS format with leading whitespace ignored. A FITS card must begin with an uppercase/numeric keyword. Lines not beginning with a FITS keyword such as comments or lower case are ignored. The user keyword output of imheader is an acceptible data file. See mkheader for further information.

DESCRIPTION

This task creates or modifies images with a choice of patterns. New images are created with the specified dimensions, datatype, and pattern. Existing images may have the pattern replace, add, or multiply the pixel values. Existing images may be modified in place or new images may be created and image sections are allowed.

For new images a set of header keywords may be added by specifying an image or data file with the header parameter (see also mkheader ). If a data file is specified lines beginning with FITS keywords are entered in the image header. Leading whitespace is ignored and any lines beginning with words having lowercase and nonvalid FITS keyword characters are ignored.

This task is the simplest one for creating empty images to be used for mosaicing with imcopy and making patterns for testing display and image operators. The replace option is generally used with image sections to place constant values in regions. The multipy option is useful for making masks of the given pattern when the values are 0 and 1.

Though the patterns make sense extending to higher dimensions they are only defined in two dimensions. One dimensional images may be thought of as the first line of the two dimensional pattern. Images with dimensions greater than 2 simply repeat the two dimensional pattern into the higher dimensions. The reason for stopping at two dimensions is simplicity.

The patterns have the following precise definitions where P(i,j) is the pixel value at column i and line j, v1 and v2 are the pattern values, size is the pattern size, ncols and nlines are the number of columns and lines in the image, int is the integer function, mod is the modulus function, and sqrt is the square root function.

                k = int ((i-1)/size), l = int ((j-1)/size)
                ksr = int (sqrt (k)), lsr = int (sqrt (l))
                slope = (v2-v1) / ((ncols+nlines-2)/size)

    constant:   P(i,j) = v1

        grid:   P(i,j) = v2   when mod(i,size)=1 or mod(j,size)=1
                P(i,j) = v1   otherwise

 coordinates:   P(i,j) = i + j * ncols

     checker:   P(i,j) = v1   when mod(k,2)=0 and mod(l,2)=0
                P(i,j) = v2   when mod(k,2)=1 and mod(l,2)=0
                P(i,j) = v2   when mod(k,2)=0 and mod(l,2)=1
                P(i,j) = v1   when mod(k,2)=1 and mod(l,2)=1

       slope:   P(i,j) = v1 + slope * (k + l) 

      square:   P(i,j) = v1   when mod(ksr,2)=0 and mod(lsr,2)=0
                P(i,j) = v2   when mod(ksr,2)=1 and mod(lsr,2)=0
                P(i,j) = v2   when mod(ksr,2)=0 and mod(lsr,2)=1
                P(i,j) = v1   when mod(ksr,2)=1 and mod(lsr,2)=1

EXAMPLES

1. Create an empty (constant value of zero) three dimensional image.

	cl> mkpattern cube ndim=3 nc=100 nl=100 n3=100

2. Replace a square region of an image with the value -1000.

	cl> mkpat alpha[201:250,1:50] v1=-1000

3. Put a grid pattern on an image to create a new image.

	cl> mkpat dev$pix out=gridpix pat=grid op=mul v1=1 v2=0

REVISIONS

MKPATTERN V2.11

Now allows ndim=0 to create dataless header.

Now allows type ushort pixel type.

SEE ALSO

imcopy, imreplace