graphics.md

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• RAW Pixels Viewer

image from bytes

• ~/code/guides/ctf/write-ups-2015/pragyan-ctf-2015/misc/255_255_255_is_the_best_color/go.py

animation

ffmpeg -framerate 75 -i 'input%04d0000.png' output.gif

# `-delay n`: 100/n FPS
# `-loop 0`: repeat forever
convert -delay 2 -loop 0 input*.png output.gif

convert

# SVG to PNG
for i in *.svg ; do inkscape -z -f "${i}" -w48 -h48 -e "${i%.svg}.png" ; done

# PCD to PNG
find . -name "*.pcd" -type f -exec convert '{}[5]' ../../pngs/'{}'.png \;

write / export from plaintext

{
  # magic, width, height, max component value
  echo "P3 250 250 255"
  for ((y=0; y<250; y++)) {
    for ((x=0; x<250; x++)) {
      # r, g, b
      echo "$((x^y)) $((x^y)) $((x|y))"
    }
  }
} | convert ppm:- png:- >foo.png

Alternatives:

• NetPBM: pnmtopng < foo.ppm > foo.png
  • Use echo/printf to write images in 5 LoC with zero libraries or headers – Vidar's Blog

seams

layer > transform > offset

light balance

duplicate layer gaussian blur invert colours layer tab > mode > overlay

lighten

duplicate layer gradient tool layer tab > mode > addition

posterize, alpha channel

https://orbitingweb.com/blog/optimizing-png-images/

xor

# highlight differences
compare i1.png i2.png -metric RMSE o.png
# render differences
composite i1.png i2.png -compose difference o.png

combine

import numpy as np
from PIL import Image

data = np.zeros((2000,2000,4), dtype=np.uint8)

for i in range(100):
    for j in range(100):
        #modify_file("flag_{}_{}.jpg".format(i,j))
        im = Image.open("flag_{}_{}.png".format(i,j))
        array = np.array(im.getdata()).reshape(20,20,4)
        data[20*i:20*(i+1), 20*j:20*(j+1)] = array

img = Image.fromarray(data, 'RGBA')
img.save('flag.png')

montage -mode concatenate -tile 1x in-*.jpg out.jpg

https://superuser.com/questions/290656/combine-multiple-images-using-imagemagick

cut

# 1366x768
convert in.png -crop "$((1366-$((1366-752+2))))x$((768-$((768-464+26))))+1+26" out.png
# 1/3 of 1366x768
convert in.png -crop "$((490-20-2))x$((736-10-34))+11+34" out.png

visual regression testing

• python - selenium webdriver save_screenshot() + Pillow ImageChops.difference()
  • https://jounileino.com/2019/05/17/visual-regression-testing.html
  • https://stackoverflow.com/questions/41721734/take-screenshot-of-full-page-with-selenium-python-with-chromedriver
• {!} changes in one element displace others => compute diff in DOM tree, style only changed elements

responsive layouts

• GitHub - redecheck/redecheck: Automatically Detecting Layout Failures in Responsive Web Pages
  • ~/Downloads/ReDeCheck - An Automatic Layout Failure Checking Tool for Responsively Designed Web Pages.pdf
  • user-defined layout constraints checked against different viewports

levels

http://www.imagemagick.org/discourse-server/viewtopic.php?t=27719

reversing gaussian blur

With G'MIC plugin:

Details > Sharpening

• Richardson-Lucy Deconvolution
• Gold-Meinel Deconvolution

aligning rotations

By FFT, what rotation?

untwist

Filters > Distorts > Whirl and Pinch...

frequency domain

Frequency Domain Image Compression and Filtering | Hacker News