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imageplt - plot a greyscale image


imageplt -d nrows ncols [ options ... ] [ file ]


imageplt provides a simple way to plot a greyscale image using plt(1) . The required arguments, nrows and ncols, specify the numbers of rows and columns in the image. The input file (or the standard input, if no input file is specified) contains only the grey levels for each pixel (0 = white, 1 = black). Each entry is an ASCII-coded decimal floating point number, separated from adjacent entries by whitespace (one or more spaces, tabs, or newlines). The first nrows entries are the grey levels for column 0 of the image, botttom to top, and each successive column from left to right of the image follows. If nrows is small, it may be convenient to arrange the image file in columns and rows corresponding to those of the image, but this is not necessary. In no case should the length of a line of input exceed 50000 bytes (defined as MAXLEN in the source).

Options include:

Generate a negative image (1 = white, 0 = black).
-x xmin xmax
Specify the range of the x-coordinates (default: xmin=0, xmax=nrows-1).
-y ymin ymax
Specify the range of the y-coordinates (default: ymin=0, ymax=ncols-1).

The output of imageplt is text in three columns, to be plotted using the -pc option of plt, as in:

imageplt -d 10 10 foo | plt 0 1 2 -pc

See Also

plt(1) , pltf(1)


imageplt is available as part of the plt package in PhysioToolkit (see SOURCES below) under the GPL.


George B. Moody (


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Updated 28 May 2015