ZAPLIN - Replaces regions in a two-dimensional NDF by bad values or by linear interpolation

Description:

This routine replaces selected areas within a two-dimensional input NDF  (specified by Parameter IN), either by filling the areas with bad values, or by linear interpolation between neighbouring data values (see Parameter ZAPTYPE). Each area to be replaced can be either a range of pixel columns extending the full height of the image, a range of pixel lines extending the full width of the image, or a rectangular region with edges parallel to the pixel axes (see Parameter LINCOL).

The bounds of the area to be replaced can be specified either by using a graphics cursor, or directly in response to parameter prompts, or by supplying a text file containing the bounds (see Parameter MODE). In the first two modes the application loops asking for new areas to zap, until told to quit or an error is encountered. In the last mode processing stops when the end of file is found. An output text file may be produced containing a description of the areas replaced (see Parameter COLOUT). This file may be used to specify the regions to be replaced in a subsequent invocation of ZAPLIN.

Usage:

zaplin in out [title] $\left\{ {\begin{tabular}{l} lincol=? \\ columns=? lines=? \\ colin=? \end{tabular} } \right.$
                     mode

Parameters:

COLIN = FILENAME (Read)

The name of a text file containing the bounds of the areas to be replaced. This parameter is only accessed if Parameter MODE is set to "File". Each record in the file must be either a blank line, a comment (indicated by a "!" or "#" in column 1), or a definition of an area to be replaced, consisting of three or four space-separated fields. If a range of columns is to be replaced, each of the first two fields should be a formatted value for the first axis of the current co-ordinate Frame  of the input NDF, and the third field should be the single character "C". If a range of lines is to be replaced, each of the first two fields should be a formatted value for the second axis of the current co-ordinate Frame, and the third field should be the single character "L". If a rectangular region is to be replaced, the first two fields should give the formatted values on axes 1 and 2 at one corner of the box, and the second two fields should give the formatted values on axes 1 and 2 at the opposite corner of the box.

COLOUT = FILENAME (Read)

The name of an output text file in which to store descriptions of the areas replaced by the current invocation of this application. It has the same format as the input file accessed using Parameter COLIN, and so may be used as input on a subsequent invocation. This parameter is not accessed if Parameter MODE is set to "File". If COLOUT is null (!), no file will be created. [!]

COLUMNS = LITERAL (Read)

A pair of x values indicating the range of columns to be replaced. All columns between the supplied values will be replaced. This parameter is only accessed if Parameter LINCOL is set to "Columns" or "Region", and Parameter MODE is set to "Interface". Each x value should be given as a formatted value for axis 1 of the current co-ordinate Frame of the input NDF. The two values should be separated by a comma, or by one or more spaces.

DEVICE = DEVICE (Read)

The graphics device to use if Parameter MODE is set to "Cursor". [Current graphics device]

IN = NDF (Read)

The input image.

LINCOL = LITERAL (Read)

The type of area is to be replaced. This parameter is only accessed if Parameter MODE is set to "Cursor" or "Interface". The options are as follows.

• "Lines" -- Replaces lines of pixels between the y values specified by Parameter LINES. Each replaced line extends the full width of the image.

• "Columns" -- Replaces columns of pixels between the x values specified by Parameter COLUMNS. Each replaced column extends the full height of the image.

• "Region" -- Replaces the rectangular region of pixels within the x and y bounds specified by Parameters COLUMNS and LINES. The edges of the box are parallel to the pixel axes.

If this parameter is specified on the command line, and Parameter MODE is set to "Interface", only one area will be replaced; otherwise a series of areas will be replaced until a null (!) value is supplied for this parameter.

LINES = LITERAL (Read)

A pair of y values indicating the range of lines to be replaced. All lines between the supplied values will be replaced. This parameter is only accessed if Parameter LINCOL is set to "Lines" or "Region", and Parameter MODE is set to "Interface". Each y value should be given as a formatted value for axis 2 of the current co-ordinate Frame of the input NDF. The two values should be separated by a comma, or by one or more spaces.

MARKER = INTEGER (Read)

This parameter is only accessed if Parameter PLOT is set to "Mark". It specifies the type of marker with which each cursor position should be marked, and should be given as an integer PGPLOT marker type. For instance, 0 gives a box, 1 gives a dot, 2 gives a cross, 3 gives an asterisk, 7 gives a triangle. The value must be larger than or equal to $-$31. [current value]

MODE = LITERAL (Read)

The method  used to obtain the bounds of the areas to be replaced. The supplied string can be one of the following options.

• "Interface" -- Bounds are obtained using Parameters COLUMNS, and LINES. The type of area to be replaced is specified using Parameter LINCOL.

• "Cursor" -- Bounds are obtained using the graphics cursor of the device specified by Parameter DEVICE. The type of area to be replaced is specified using Parameter LINCOL. The WCS information stored with the picture in the graphics database  is used to map the supplied cursor positions into the pixel co-ordinate Frame of the input NDF. A message is displayed indicating the co-ordinate Frame in which the picture and the output NDF were aligned. Graphics may be drawn over the image indicating the region to be replaced (see Parameter PLOT).

• "File" -- The bounds and type of each area to be replaced are supplied in the text file specified by Parameter COLIN.

[current value]

NOISE = _LOGICAL (Read)

This parameter is only accessed if Parameter ZAPTYPE is set to "Linear". If a TRUE value is supplied, gaussian noise is added to each interpolated pixel value. The variance of the noise is equal to the variance of the data value being replaced. If the data variance is bad, no noise is added. If the input NDF has no VARIANCE  component, variances equal to the absolute data value are used. This facility is provided for cosmetic use. [FALSE]

OUT = NDF (Write)

The output image.

PLOT = LITERAL (Read)

The type of graphics to be used to mark each cursor position. The appearance of these graphics (colour, size, etc.) is controlled by the STYLE parameter. PLOT can take any of the following values.

• "Adapt" -- Causes "Box" to be used if a region is being replaced, "Vline" is a range of columns is being replaced, and "Hline" if a range of lines is being replaced.

• "Box" -- A rectangular box with edges parallel to the edges of the graphics device is drawn with the two specified positions at opposite corners.

• "Mark" -- Each position is marked by the symbol specified by Parameter MARKER.

• "None" -- No graphics are produced.

• "Vline" -- A vertial line is drawn through each specified position, extending the entire height of the selected picture.

• "Hline" -- A horizontal line is drawn through each specified position, extending the entire width of the selected picture.

[current value]

STYLE = LITERAL (Read)

A group of attribute settings describing the style to use when drawing the graphics specified by Parameter PLOT.

A comma-separated list of strings should be given in which each string is either an attribute setting, or the name of a text file preceded by an up-arrow character "$\wedge$". Such text files should contain further comma-separated lists which will be read and interpreted in the same manner. Attribute settings are applied in the order in which they occur within the list, with later settings overriding any earlier settings given for the same attribute.

Each individual attribute setting should be of the form:

$<$name$>$=$<$value$>$

where $<$name$>$ is the name of a plotting attribute, and $<$value$>$ is the value to assign to the attribute. Default values will be used for any unspecified attributes. All attributes will be defaulted if a null value (!) is supplied. See Plotting Attributes for a description of the available attributes. Any unrecognised attributes are ignored (no error is reported).

The appearance of vertical and horizontal lines is controlled by the attributes Colour(Curves), Width(Curves), etc. (the synonym Lines may be used in place of Curves). The appearance of boxes is controlled by the attributes Colour(Border), Size(Border), etc. (the synonym Box may be used in place of Border). The appearance of markers is controlled by attributes Colour(Markers), Size(Markers), etc. [current value]

TITLE = LITERAL (Read)

Title for the output image. A null value (!) propagates the title from the input image to the output image. [!]

USEAXIS = GROUP (Read)

USEAXIS is only accessed if the current co-ordinate Frame of the input NDF has more than two axes. A group of two strings should be supplied specifying the two axes spanning the plane containing the areas to be replaced. Each axis can be specified using one of the following options.

• Its integer index within the current Frame of the output NDF (in the range 1 to the number of axes in the current Frame).

• Its Symbol  string such as "RA" or "VRAD".

• A generic option where "SPEC" requests the spectral axis, "TIME" selects the time axis, "SKYLON" and "SKYLAT" picks the sky longitude and latitude axes respectively. Only those axis domains present are available as options.

A list of acceptable values is displayed if an illegal value is supplied. If a null (!) value is supplied, the axes with the same indices as the first two significant NDF pixel axes are used. [!]

ZAPTYPE = LITERAL (Read)

The method used to choose the replacement pixel values. It should be one of the options below.

• "Bad" -- Replace the selected pixels by bad values.

• "Linear" -- Replace the selected pixels using linear interpolation. If a range of lines is replaced, then the interpolation is performed vertically between the first non-bad pixels above and below the selected lines. If a range of columns is replaced, then the interpolation is performed horizontally between the first non-bad pixels to the left and right of the selected columns. If a rectangular region is replaced, then the interpolation is bi-linear between the nearest non-bad pixels on all four edges of the selected region. If interpolation is not possible (for instance, if the selected pixels are at the edge of the array) then the pixels are replaced with bad values. ["Linear"]

Examples:

zaplin out=cleaned colout=fudge.dat

Assuming the current value of Parameter MODE is "Cursor", this will copy the NDF associated with the last DATA picture to an NDF called cleaned, interactively replacing areas using the current graphics device. Linear interpolation is used to obtain the replacement values. A record of the areas replaced will be stored in a text file named fudge.dat.

zaplin grubby cleaned i lincol=r columns="188 190" lines="15 16"

This replaces a region from pixel (188, 15) to (190, 16) within the NDF called grubby and stores the result in the NDF called cleaned. The current co-ordinate Frame in the input NDF should be set to PIXEL first (using WCSFRAME). The replacement is performed using linear interpolation.

zaplin grubby(6,,) cleaned i lincol=r columns="188 190"

This replaces columns 188 to 190 in the 6th y-z plane region within the NDF called grubby and stores the result in the NDF called cleaned. The current co-ordinate Frame in the input NDF should be set to PIXEL first (using WCSFRAME). The replacement is performed using linear interpolation.

zaplin m42 m42c f colin=aaoccd1.dat zaptype=b

This flags with bad values the regions in the NDF called m42 defined in the text file called aaoccd1.dat, and stores the result in an NDF called m42c.

zaplin m42 m42c f colin=aaoccd1.dat noise

As above except that linear interpolation plus cosmetic noise are used to replace the areas to be cleaned rather than bad pixels.

Notes:

• Bounds supplied in Interface and File mode are transformed into the PIXEL Frame of the input NDF before being used.

• Complicated results arise if the axes of the current Frame of the input NDF are not parallel to the pixel axes. In these cases it is usually better to switch to the PIXEL Frame (using WCSFRAME) prior to using ZAPLIN. Roughly speaking, the range of pixel lines and/or columns which are replaced will include any which intersect the specified range on the current-Frame axis.

• When using input files care should be taken to ensure that the co-ordinate system used in the file matches the current co-ordinate Frame of the input NDF.

• If the input NDF is a section of an NDF  with a higher dimensionality, the "lines" and "columns" are with respect to the two-dimensional section, and do not necessarily refer to the first and second dimensions of the NDF as a whole. See the "Examples".

Related Applications

KAPPA: ARDMASK, CHPIX, FILLBAD, GLITCH, NOMAGIC, REGIONMASK, SEGMENT, SETMAGIC; FIGARO: CSET, ICSET, NCSET, TIPPEX.

Implementation Status:

• This routine correctly processes the AXIS, DATA, QUALITY, VARIANCE, LABEL, TITLE, UNITS, WCS, and HISTORY  components of the input NDF and propagates all extensions.

• Processing of bad pixels and automatic quality masking are supported.

• All non-complex numeric data types can be handled.