Legacy ImageMagick Discussions Archive

Hello everybody! Could you help me to add white margins to image in pbm format? For example, 2 cm for top and bottom, 1,5 for left and rigt.

You will have to convert from cm or inches to pixels using the image's density (nominally 72 dpi, but it may be different). Then you can simply use -bordercolor white -border X, where X is in pixels (see http://www.imagemagick.org/Usage/crop/#border), if you want it uniform all around. If you want different borders, then use -splice (see http://www.imagemagick.org/Usage/crop/#splice)

You can find the density or resolution and units for an image from string formats %x and %y from http://www.imagemagick.org/script/escape.php

convert -units pixelsperinch zelda3.png -density 72 zelda3.pnm
convert zelda3.pnm -format "%x x %y" info:
72 Undefined x 72 Undefined

Does PNM format support units?

You would then convert 72 dpi (presumably) to centimeters and then figure out how many pixels that means for a 2 cm border.

Here is an example:

# create test image:
convert zelda3.jpg -density 72 -units pixelsperinch zelda3_72dpi.jpg

# process it to add a 2 cm border
borderwidth=2 #assume centimeters
res=`convert zelda3_72dpi.jpg -format "%x" info:`
density=`echo "$res" | cut -d\ -f1`
units=`echo "$res" | cut -d\ -f2`
echo "density=$density; units=$units"
if [ "$units" = "PixelsPerCentimeter" ]; then
borderpix=`convert xc: -format "%[fx:2*$density]" info:`
elif [ "$units" = "PixelsPerInch" -o "$units" = "Undefined" ]; then
borderpix=`convert xc: -format "%[fx:round(2*$density/2.54)]" info:`
fi
echo "borderpix=$borderpix"
convert zelda3_72dpi.jpg -bordercolor white -border $borderpix zelda3_72dpi_border.jpg

Thank you! And is it possible to delete a part of borders? For example, I need to delete 2 cm from top and 3 from bottom.

see -shave at http://www.imagemagick.org/Usage/crop/#shave

but you again need to convert from cm to pixels using the density and units.