imgproc

An experimental and unpolished image processing utility for the command line.

Allow to manipulate and combine up to 9 images using a simple SDL limited to channel access and basic functions.

Installing

With npm do:

npm install imgproc -g

SDL

Input variables : r1 is the red channel of the first input image, g2 is the green channel of the second input image, b3 is the blue channel of the third input image, a9 is the alpha channel of the ninth input image, etc.

Numerical constants : 0, 0.001, 1923., -5, etc.

Functions :

• min
• max
• add
• sub
• mul
• div
• avg
• mod
• pow
• rand
• sin
• cos
• floor
• ceil
• mix

Recipes

Limit to a single channel

imgproc img/trees.png -o outputs/red-channel-only.png --red="r1"

Invert colors

imgproc img/trees.png -o outputs/invert-colors.png --red="sub(1,r1)" --green="sub(1,g1)" --blue="sub(1,b1)" --alpha="a1"

Desaturate (crudely)

imgproc img/trees.png -o outputs/desaturate.png --red="avg(r1,g1,b1)" --green="avg(r1,g1,b1)" --blue="avg(r1,g1,b1)" --alpha="a1"

Desaturate by 70 percents

imgproc img/trees.png -o outputs/desaturate-seventy-percents.png --red="mix(r1,avg(r1,g1,b1),0.7)" --green="mix(g1,avg(r1,g1,b1),0.7)" --blue="mix(b1,avg(r1,g1,b1),0.7)" --alpha="a1"

Desaturate all but blue

imgproc img/trees.png -o outputs/desaturate-all-but-blue.png --red="avg(r1,g1,b1)" --green="avg(r1,g1,b1)" --blue="max(b1,avg(r1,g1,b1))" --alpha="a1"

Darken

imgproc img/trees.png -o outputs/darken.png --red="pow(r1,1.3)" --green="pow(g1,1.3)" --blue="pow(b1,1.3)" --alpha="a1"

Lighten

imgproc img/trees.png -o outputs/lighten.png --red="add(0.25,mul(0.8,pow(r1, 0.5)))" --green="add(0.25,mul(0.8,pow(g1, 0.5)))" --blue="add(0.25,mul(0.8,pow(b1, 0.4)))" --alpha="a1"

Gameboy filter

imgproc img/trees.png -o outputs/gameboy.png --red="add(0.07,div(floor(mul(pow(avg(r1,g1,b1),0.7),4)),3.8))" --green="add(0.1,div(floor(mul(pow(avg(r1,g1,b1),0.7),4)),3.3))" --blue="add(0.02,div(floor(mul(pow(avg(r1,g1,b1),0.7),4)),3.8))" --alpha="a1"

Blend two images

imgproc img/trees.png img/mask.png -o outputs/mix.png --red="mix(r1,r2,0.5)" --green="mix(g1,g2,0.5)" --blue="mix(b1,b2,0.5)" --alpha="mix(a1,a2,0.5)"

Use a B/W image as an alpha mask

imgproc img/trees.png img/mask.png -o outputs/mask-alpha.png --red="r1" --green="g1" --blue="b1" --alpha="avg(r2,g2,b2)"

Combine two heightmaps in a single image

imgproc img/trees.png img/mask.png -o outputs/combined.png --red="avg(r1,g1,b1)" --green="avg(r2,g2,b2)" --blue="0.5" --alpha="1"

Mix two images using the multiply blend mode

imgproc img/trees.png img/mask.png -o outputs/multiply.png --red="mul(r1,r2)" --green="mul(g1,g2)" --blue="mul(b1,b2)" --alpha="avg(a1,a2)"

Mix two images using the screen blend mode

imgproc img/trees.png img/mask.png -o outputs/screen.png --red="sub(1,mul(sub(1,r1),sub(1,r2)))" --green="sub(1,mul(sub(1,g1),sub(1,g2)))" --blue="sub(1,mul(sub(1,b1),sub(1,b2)))" --alpha="avg(a1,a2)"

Changelog

0.1.1 (2017.08.13) :

• Add proper credits for example image in readme.

0.1.0 (2017.08.13) :

• First release.

License

MIT

Additional credits

The example image is a picture licensed as CC-BY-NC-SA by pohcao34 on Flickr (see original).