bak

Author: cirosantilli

README.md

@@ -268,7 +268,7 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
         1. [libnotify](libnotify.md)
         1. [zenity](zenity.md)
     1.  Screenshots
-        1. [recordMyDesktop](recordMyDesktop.md)
+        1. [recordMyDesktop](record-my-desktop.md)
         1. [xwd](xwd.md)
     1.  [Screensaver](screensaver.md)
     1.  [IBus](ibus.md)

dot/README.md

@@ -2,6 +2,6 @@
 
 Plain text graph description language and name of a program that converts `.dot` files to images.
 
-Graphviz project.
+Front-end tool of the Graphviz project, which is backed by a powerful library.
 
 Can also describe graph appearance.

dot/bold-title.dot

@@ -0,0 +1,12 @@
+// http://stackoverflow.com/questions/6171344/graphviz-record-node-with-a-bold-title
+digraph i { 
+  "node" [
+    label =<
+             <table border="0" cellborder="1" cellspacing="0">
+                 <tr><td><b>title</b></td></tr>
+                 <tr><td>field 1</td></tr>
+             </table>
+           >
+    shape = "none"
+  ];  
+}

dot/graph.dot

@@ -1,5 +1,5 @@
-// Undirected
-graph graphname {
+// Undirected.
+graph {
     a -- b -- c;
     b -- d;
 }

dot/html.dot

@@ -0,0 +1,5 @@
+graph {
+    1 [label=<<b>bold</b>>]
+    2 [label=<x<sub>sub</sub>>]
+    1 -- 2
+}

dot/node-shape-point-label.dot

@@ -0,0 +1,11 @@
+// TODO how to make a graph with shape=point and labels?
+// - http://www.graphviz.org/content/external-labels
+// - http://stackoverflow.com/questions/23018684/annotation-outside-a-node-in-dot
+// - http://www.graphviz.org/content/how-use-xlp-attribute-positioning-external-labels-xlabel
+// - http://stackoverflow.com/questions/30689533/graphviz-graph-positioning-xlabels
+graph {
+    node [shape=point];
+    1 [xlabel="a"]
+    2 [xlabel="b"]
+    1 -- 2;
+}

dot/tmp.dot

@@ -0,0 +1,6 @@
+digraph G {
+    a [ label=<&#945;>]
+    b [ label=<&#946;>]
+    c [ label="I love <b>&alpha;</b> and &beta;" ]
+    a -> b -> c
+}

dot/unicode.dot

@@ -0,0 +1,4 @@
+graph {
+    "x²" -- "x³"
+    "α" -- "β"
+}

ffmpeg.md

@@ -104,10 +104,14 @@ From there on, Bash it up.
 - <http://askubuntu.com/questions/380199/converting-images-into-video>
 - <http://stackoverflow.com/questions/16315192/avconv-make-a-video-from-a-subset-on-images>
 - <https://trac.ffmpeg.org/wiki/Create%20a%20video%20slideshow%20from%20images>
+- <http://unix.stackexchange.com/questions/68770/converting-png-frames-to-video-at-1-fps>
+- <http://stackoverflow.com/questions/19267443/playback-issues-in-vlc-with-low-fps-video-from-images-using-ffmpeg>
 
 Just works:
 
-    ffmpeg -framerate 4 -pattern_type glob -i '*.jpg' -c:v libx264 out.mp4
+    ffmpeg -framerate 1 -pattern_type glob -i '*.png' -c:v libx264 -r 30 -pix_fmt yuv420p out.mp4
+
+`-r 30` to use a standard frame rate and be more compatible, see: <http://stackoverflow.com/questions/19267443/playback-issues-in-vlc-with-low-fps-video-from-images-using-ffmpeg/41797724#41797724>
 
 ### Smooth transitions
 
@@ -178,3 +182,31 @@ A few URLs that can be accessed from the browser:
 ## udp protocol
 
 An FFmpeg invention it seems: <http://stackoverflow.com/questions/27930879/what-is-ffmpegs-udp-protocol>
+
+## Trim by time
+
+## Cut by time
+
+- <http://stackoverflow.com/questions/18444194/cutting-the-videos-based-on-start-and-end-time-using-ffmpeg/40244234>
+- <http://superuser.com/questions/138331/using-ffmpeg-to-cut-up-video>
+
+Best command:
+
+    ffmpeg -i in.ogv -ss 00:00 -to 03:30 -c copy out.ogv
+
+## Concatenate
+
+- <http://ffmpeg.org/faq.html#How-can-I-concatenate-video-files>
+- <http://stackoverflow.com/questions/7333232/concatenate-two-mp4-files-using-ffmpeg>
+
+Best command:
+
+    ffmpeg -i concat:"in1.ogv|in2.ogv" -c copy out.ogv
+
+## Merge audio and video
+
+<http://superuser.com/questions/277642/how-to-merge-audio-and-video-file-in-ffmpeg>
+
+Yeah, this works on VLC and YouTube:
+
+    ffmpeg -i video.mp4 -i audio.mp3 -c copy output.mkv

imagemagick.md

@@ -144,6 +144,10 @@ Force modified aspect ratio:
 
 	convert large.png -resize '50x100!' small.png
 
+## Resize to fixed aspect ratio, fill extra space black
+
+    convert in.png -resize 800x600 -background black -gravity center -extent 800x600 out.png
+
 ### trim
 
 Automagically remove white background.
@@ -252,6 +256,10 @@ TODO what does `-colorspace hsl` mean? Do output formats support HSL?
 
         convert -threshold 50 a.jpg b.jpg
 
+    Operate on alpha channel only:
+
+        convert apple.svg -scale 512x512 -channel alpha -threshold 50% +channel apple.png
+
 -   `-monochrome`: seems to generate a black and white binary image with a good dithering.
 
         convert -monochrome a.jpg b.jpg
@@ -260,6 +268,7 @@ TODO what does `-colorspace hsl` mean? Do output formats support HSL?
 
     <http://www.imagemagick.org/Usage/quantize/#monochrome>
 
+
 ### extent
 
 Keep only the 50x50 central square of an image:
@@ -288,6 +297,16 @@ Horizontally:
 
     convert image.png -background white -alpha remove white.png
 
+### Make white also transparent
+
+Raw:
+
+    convert in.png -transparent white out.png
+
+Hard threshold:
+
+    convert in.png -threshold 50% -transparent white out.png
+
 ### GIF operations
 
 GIF to several images:
@@ -341,3 +360,7 @@ Checkerboard:
 ## Trivia
 
 - http://arstechnica.com/security/2016/05/exploits-gone-wild-hackers-target-critical-image-processing-bug/
+
+## SVG
+
+Not very good support as of 6.8.9.

od.md

@@ -87,6 +87,7 @@ Best command for computational use:
 
 1 and 2 means how many bytes per block.
 
+
 Example:
 
     echo -n ab | od -tx1
@@ -136,8 +137,7 @@ More precisely, there are the following cases:
 
 - if the byte has a corresponding non whitespace ASCII character or space, print that character.
 
-- else if the character has a corresponding backslash `\\` C escape sequence,
-    print that sequence. Ex: 0 is `\0`.
+- else if the character has a corresponding backslash `\\` C escape sequence, print that sequence. Ex: 0 is `\0`.
 
 - else print the octal value of the byte as in `-to1`.
 
@@ -265,6 +265,12 @@ Output:
     0000048 79 20 7a 0a
     0000052
 
+### Remove address lines
+
+<http://unix.stackexchange.com/questions/192937/removing-line-numbers-from-ods-output>
+
+    -An
+
 ## N
 
 Maximum number of bytes to read.

openai-gym.md

@@ -0,0 +1,25 @@
+# OpenAI Gym
+
+<https://github.com/openai/gym/issues>, tested at `77568accd7f698ae67937da0099fa58a037a96fd`.
+
+True getting started:
+
+    python examples/agents/random.py
+
+Minimal example: <https://github.com/cirosantilli/gym/tree/random-agent-minimize-print>
+
+Shows GUI, and videos of runs dumped to `tmp`.
+
+Human controlled agent:
+
+    python examples/agents/keyboard_agent.py
+
+but it does not have frame rate limiting, so it is useless.
+
+Your first intelligent player:
+
+    python examples/agents/cem.py
+
+but the interface is dedicated for the pole game.
+
+TODO: make a minimal interface that adapts to any game. This seems to be the case: <https://github.com/openai/universe-starter-agent/blob/master/README.md>

recordMyDesktop.md renamed to record-my-desktop.md

@@ -16,3 +16,7 @@ Most useful command:
 - save output to `out.ogv`, `out-1.ogv`, ...
 
 Use if from a drop-down terminal like Guake so in the 2 seconds you can make it disappear.
+
+Global shortcuts: <http://askubuntu.com/questions/200952/what-is-a-desktop-recorder-with-global-shortcuts>
+
+Screen area selection: <http://askubuntu.com/questions/156606/how-can-i-accurately-select-an-area-of-screen-to-record-when-using-recordmydeskt>

unicode.md

@@ -149,3 +149,7 @@ Also, it contains NUL characters all over for ASCII, which requires greater care
 ## Largest common Unicode gliph
 
 <https://www.quora.com/What-are-the-coolest-Unicode-characters/answer/Ciro-Santilli-%E5%85%AD%E5%9B%9B%E4%BA%8B%E4%BB%B6-%E6%B3%95%E8%BD%AE%E5%8A%9F-%E7%BA%B3%E7%B1%B3%E6%AF%94%E4%BA%9A-%E5%A8%81%E8%A7%86>
+
+## Math simulation
+
+<https://en.wikipedia.org/wiki/Unicode_subscripts_and_superscripts>