GNU Astronomy Utilities manual

6.1.4.2 ImageCrop output

When a catalog is given, the value of --output (see Common options) will be seen as the directory to store the output cropped images. In such cases, the outputs will consist of two parts: a variable part (the row number of each target starting from 1) along with a fixed string which you can set with the --suffix option. Note that in catalog mode, only one image can be input.

When the crop box is specified on the command line, the value to --output will be used as a file name. If no output is specified or if it is a directory, the output file name will follow the automatic output names of Gnuastro, see Automatic output for the input image.

The header of each output cropped image will contain the names of the input image(s) it was cut from. If a name is longer than the 70 character space that the FITS standard allows for header keyword values, the name will be cut into several keywords from the nearest slash (/). The keywords have the following format: ICFn_m. Where n is the number of the image used in this crop and m is the part of the name. Following the name is another keyword named ICFnPIX which shows the pixel range from that input image in the same syntax as Crop section syntax.

Once done, a log file will be created in the current directory named astimgcrop.log. This file will keep the names of all the outputs along with the number of images that were used in them and also whether the central pixels of the cropped image are full. There are also comments on the top explaining basic information about the run. If the log file cannot be created (for example you don’t have write permission in the directory you are running ImageCrop in) it will not be created (unless --individual is called). You can see the same results in verbose mode on the command line in such cases.

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GNU Astronomy Utilities manual, November 2015.