ppmshadow

Add drop shadow effect to PPM images

TLDR

Add a default drop shadow

$ ppmshadow [input.ppm] > [output.ppm]

Specify blur radius for shadow softness

$ ppmshadow -b [8] [input.ppm] > [output.ppm]

Specify shadow offset direction

$ ppmshadow -x [5] -y [5] [input.ppm] > [output.ppm]

Create a translucent shadow

$ ppmshadow -t [input.ppm] > [output.ppm]

ppmshadow adds a drop shadow effect to a PPM image, creating the appearance of the image floating above a background. The shadow is created by blurring a darkened copy of the image and placing it offset behind the original.The blur radius controls shadow softness, while x and y offsets control the apparent light direction. The -t option creates a translucent shadow that allows the background to show through. Part of the Netpbm toolkit.The input image must have a transparent (black) background area for the shadow to be visible. The output image is larger than the input by the shadow offset.

PARAMETERS

FILE

Input PPM file. Reads from stdin if omitted.

-b N

Blur radius controlling shadow softness (default: 11).

-x N

Horizontal shadow offset in pixels (default: blur radius / 2).

-y N

Vertical shadow offset in pixels (default: same as -x).

-t

Create a translucent shadow instead of a solid black one.

INSTALL

sudo apt install netpbm

sudo dnf install netpbm

sudo pacman -S netpbm

sudo apk add netpbm-extras

sudo zypper install netpbm

brew install netpbm

nix profile install nixpkgs#netpbm

CAVEATS

Requires the image to have a transparent (black) background around the subject for the shadow to appear correctly. Internally uses pnmconvol for blurring, which can be slow for large blur radii. Part of the Netpbm suite.

HISTORY

ppmshadow was created by John Walker as part of the Netpbm toolkit for image shadow effect generation.