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Published by Silveira on 2015-06-16

Part of the board games collection at work.. from Instagram: http://ift.tt/1JWf1Ku

Published by Silveira on 2015-06-14

Arrogant Bastard Ale – Stone Brewing. from Instagram: http://ift.tt/1JS2WpJ

Published by Silveira on 2015-06-14

@suyanevom driving and me as copilot. Copying an Akira Toriyama drawing. #Micron #Pigma #Gimp #drawing #draft

from Instagram: http://ift.tt/1BbQ38x

Published by Silveira on 2015-06-13

trail at the Theodore Roosevelt Island.

from Instagram: http://ift.tt/1ebBVBZ

Java, printing arrays

Published by Silveira on 2015-06-05

As I keep forgetting, this post is to remind me that Java Java doesn’t have a pretty toString() for arrays objects, and it does for Lists.

[java]import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;

public class ListsExample {
public static void main (String args[]) {
// as an array
String[] list1 = {"a","b","c"};
System.out.println(Arrays.toString(list1));

// as an List provided by Arrays
List<String> list2 = Arrays.asList("d", "e", "f");
System.out.println(list2);

// as an implementation of the interface List
// ArrayList (could also be LinkedList, Vector, etc)
List<String> list3 = new ArrayList<String>();
list3.add("g");
list3.add("h");
list3.add("i");
System.out.println(list3);
}
}
[/java]

The output is:

[a, b, c]
[d, e, f]
[g, h, i]

Tmux: keep same directory in new windows

Published by Silveira on 2015-05-28 
# open/split windows in the same dir
bind '"' split-window -c "#{pane_current_path}"
bind % split-window -h -c "#{pane_current_path}"
bind c new-window -c "#{pane_current_path}"

In your ~/.tmux.conf.

To source it in your open tmux:
[bash]
:source-file ~/.tmux.conf
[/bash]

Or in any shell:
[bash]
tmux source-file ~/.tmux.conf
[/bash]

Visual Cryptography

Published by Silveira on 2015-05-07
Visual_crypto_animation_demo

Two basic articles on visual cryptography:

One interesting thing about this schema is that can be applied for stenography and can be simply implemented physically using only shadows.

Update: a shorter explanation with examples.

See too: One Time Pad Using Gimp.

ImageMagick, four point perspective distortion in a video

Published by Silveira on 2014-12-07

Step 1) Download the video from Youtube using JDownloader. The best one was the original Japanese upload, The Game Awards 2014 出展映像 ゼルダの伝説 最新作, which is 720p. I saved this file as zelda_720p.mp4.

Step 2) Transform the video in a series of PNGs.

[bash]mplayer -nosound -vo png:z=9 zelda_720p.mp4[/bash]

This generated image files ranging from 00000001.png to 00007563.png.

Step 3)
Using Gimp, find the 2 sets of 4 points for the perspective. The first in red is the source and the one in blue is the destination.

zelda video four point perspective

Step 4) Apply ImageMagick’s four point perspective distortion in each image using a ShellScript.

[bash]
#!/bin/sh
for image in *.png;
do
convert $image -matte -virtual-pixel transparent \
-distort Perspective \
‘60,90 0,0 50,415 0,720 582,418 1280,720 589,147 1280,0’ \
p_$image
done
[/bash]

Now I have images in the format p_00000001.png to p_00007563.png. Because PNG is a lossless format, the perspective lost less information in this step than it would if step 2 was outputting jpgs.

Step 5) Convert frames to jpgs using ImageMagick and ShellScript.

[bash]
#!/bin/sh
for image in p_*.png;
do
convert $image &quot;${image/.png/}.jpg&quot;
done
[/bash]

Where “${image/.png/}.jpg” removes the .png in the image string.

Ps: this step is not really necessary as you could use png as input to ffmpeg.

Step 6) Convert jpgs in a video.

[bash]
ffmpeg -start_number 0 -i ‘%08d.jpg’ -c:v libx264 output.mp4
[/bash]

‘%08d.jpg’ means a 8 digits filled with zeros in the left followed by .jpg, in this case 00000001.jpg to 00007563.jpg.

With this, I have the output.mp4 video ready to upload.

The whole process took several hours and a total 13GiB, although the final video has only 96 MiB. This could be optimized using pipelines and parallelism if it was needed to repeat the process.

HackerNews discussion: https://news.ycombinator.com/item?id=8713070