Split image and netpbm

cirosantilli · cirosantilli · commit 492dbf28213c · 2015-09-25T17:07:24.000+02:00
diff --git a/README.md b/README.md
@@ -188,10 +188,11 @@ Includes Linux concepts and utilities that work on Linux, not necessarily in the
     1.  [Book](book.md): PDF, DJVU.
     1.  [Dictionary](dictionary.md): dictionary formats
     1.  [Game](game.md): games, emulation
-    1.  [Image](image/): images, photos
+    1.  [Image](image.md)
         1. [GIMP](gimp.md)
-        1. [gnuplot](gnuplot)
-        1. [imagemagick](imagemagick.md)
+        1. [NetPBM](netpbm/)
+        1. [gnuplot](gnuplot/)
+        1. [ImageMagick](imagemagick.md)
     1.  [Video](video.md): videos, films, subtitles
 1.  File sharing
     1. [Dropbox](dropbox.md)
diff --git a/book/README.md b/book/README.md
@@ -30,7 +30,7 @@ Formats that contain image, text, fonts such as PDF or DJVU but not not formats
 
 -   MOBI: Mobipocket company, free format, bought by Amazon. TODO vs EPUB.
 
--   RTF: Rich Text Format, proprietary Microsoft
+-   RTF: Rich Text Format, proprietary Microsoft. Can be opened with `fbreader`.
 
 ## Viewers
 
diff --git a/dev-filesystem.md b/dev-filesystem.md
@@ -2,6 +2,8 @@
 
 Contains device driver files, and things related to device drivers like symlinks that give nice names to device drives.
 
+Files are documented under `man 4`.
+
 To understand what is going on, make a minimal device driver yourself. This is not documented here. Prerequisites you will learn when you do that:
 
 - what do the type, major and minor numbers mean
@@ -248,3 +250,11 @@ Bash also implements it as a built-in magic path.
 Useful when annoying programs don't follow the usual convention of `-` for stdout / stdin in the place of files, e.g.: <http://www.serverfault.com/questions/329150/is-there-a-way-to-make-objdump-read-from-stdin-instead-of-file>
 
 But it does not work all the time, since those programs may not implement `-` because they rely on `seek` calls which are not supported on pipes.
+
+## /dev/rtc
+
+    man rtc
+
+Real time clock.
+
+TODO example.
diff --git a/image.md b/image.md
@@ -64,38 +64,6 @@ Bit by bit, no compression.
 
 Specified by Microsoft.
 
-### Netpbm
-
-- PBM: black and white (1 or 0!)
-- PGM: gray scale
-- PPM: color
-
-Those three formats are also collectively knows as PNM, Portable aNymap Format.
-
-Mainly used in Linux.
-
-Bad browser support.
-
-Very simple to edit on a text editor because ASCII based.
-
-Not compressed, so not very memory efficient.
-
-Magic numbers: first thing in file, specifies the exact format. Cannot be determined by extension alone because of binary/ASCII forms.
-
-- `P1`: PBM ASCII
-- `P2`: PGM ASCII
-- `P3`: PPM ASCII
-- `P4`: PBM binary
-- `P5`: PGM binary
-- `P6`: PPM binary
-
-An example to differentiate ASCII from binary. For PBM:
-
-- ASCII: 1 byte per pix.
-- in binary 1 *bit* per pixel.
-
-To view the minimalistic examples in this repo, open them with an image editor and do a huge zoom.
-
 ### TIF
 
 Lossless or lossy, in practice lossless applications only.
diff --git a/image/.gitignore b/image/.gitignore
diff --git a/image/Makefile b/image/Makefile
diff --git a/image/pbm.pbm b/image/pbm.pbm
diff --git a/image/pgm.pgm b/image/pgm.pgm
diff --git a/image/ppm.ppm b/image/ppm.ppm
diff --git a/image/svg.svg b/image/svg.svg
diff --git a/imagemagick.md b/imagemagick.md
@@ -58,6 +58,14 @@ Resize to fixed width of 100 px, height maintains original proportion:
 
 	convert large.png -resize 100x small.png
 
+Fixed height:
+
+	convert large.png -resize x100 small.png
+
+Force modififed aspect ratio:
+
+	convert large.png -resize '50x100!' small.png
+
 ### crop
 
 `10x10`: rectangle to keep:
@@ -76,7 +84,7 @@ Cannot give top left corner in percentage
 
 Bottom 50 percent:
 
-        convert -gravity south -crop 100x50% a.jpg b.jpg
+    convert -gravity south -crop 100x50% a.jpg b.jpg
 
 ### color
 
@@ -104,6 +112,28 @@ Bottom 50 percent:
 
         convert -level -100,100 a.jpg b.jpg
 
+### extent
+
+Keep only the 50x50 central square of an image:
+
+    convert in.png -gravity center -extent 50x50 out.png
+
+Percentage version:
+
+    convert in.png -gravity center -extent '50%x50%' out.png
+
+### append
+
+Paste multimple images into one vertically: <http://superuser.com/questions/290656/combine-multiple-images-using-imagemagick>
+
+    convert -append in-*.jpg out.jpg
+
+Size is not corrected automatically.
+
+Horizontally:
+
+    convert +append in-*.jpg out.jpg
+
 ### Transparency to white
 
 <http://stackoverflow.com/questions/2322750/replace-transparency-in-png-images-with-white-background>
diff --git a/netpbm/.gitignore b/netpbm/.gitignore
@@ -0,0 +1 @@
+*.png
diff --git a/netpbm/Makefile b/netpbm/Makefile
@@ -0,0 +1,10 @@
+.POSIX:
+.PHONY: all clean
+
+all:
+	convert pbm.pbm pbm.png
+	convert pgm.pgm pgm.png
+	convert ppm.ppm ppm.png
+
+clean:
+	rm *.png
diff --git a/netpbm/README.md b/netpbm/README.md
@@ -0,0 +1,26 @@
+# NetPBM
+
+Simple text based or binary family of uncompressed image formats.
+
+Suitable for simple script generation.
+
+Those formats are also collectively knows as PNM, Portable aNymap Format.
+
+Mainly used in Linux.
+
+Bad browser support, but can be viewed well with many Linux viewers, including `eog` and Krusader. Make sure to do a huge zoom. Those viewers may do dithering by default.
+
+Magic numbers: first thing in file, specifies the exact format. Cannot be determined by extension alone because of binary/ASCII forms.
+
+- `P1`: `.pbm` ASCII
+- `P2`: `.pgm` ASCII
+- `P3`: `.ppm` ASCII
+- `P4`: `.pbm` binary
+- `P5`: `.pgm` binary
+- `P6`: `.ppm` binary
+
+Where:
+
+- `.pbm`: binary
+- `.pgm`: grayscale
+- `.ppm`: RGB
diff --git a/netpbm/pbm.pbm b/netpbm/pbm.pbm
@@ -0,0 +1,5 @@
+P1
+# The image is 3 x 2.
+3 2
+0 1 0
+1 0 1
diff --git a/netpbm/pgm.pgm b/netpbm/pgm.pgm
@@ -0,0 +1,8 @@
+P2
+# Image is 3 x 3.
+3 3
+# 9 is the maxium value (white) for each pixel.
+9
+0 1 2
+4 5 6
+7 8 9
diff --git a/netpbm/ppm.ppm b/netpbm/ppm.ppm
@@ -0,0 +1,8 @@
+P3
+# The image is 3 x 2.
+3 2
+# 255 is the maximum value for RGB.
+255
+# Alignment is optional: a single space would do
+255   0   0     0 255   0     0   0 255
+255 255   0   255 255 255     0   0   0
diff --git a/sysfs.md b/sysfs.md
@@ -88,7 +88,7 @@ which is provided by the hwdata package <https://git.fedorahosted.org/hosted/hwd
     8086 Intel Corporation
         0154  3rd Gen Core processor DRAM Controller
 
-### TODO
+TODO:
 
 - why do many devices are shown under PCI, but I think PCI was replaced by PCIe a long time ago.
 
@@ -100,17 +100,34 @@ Updates
 
 Block devices.
 
+Convenience only: all device directories point to `/sys/devices`
+
 <https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-block>
 
 ### removable
 
 <http://unix.stackexchange.com/questions/125961/how-to-tell-if-a-scsi-device-is-removable>
 
-TODO what does it mean exacly? My main hard disk was not removable, but my USB was:
+TODO what does it mean exactly? My main hard disk was not removable, but my USB was:
 
     cat /sys/block/sda/removable
     cat /sys/block/sdb/removable
 
+## /sys/class
+
+Devices grouped by category.
+
+This is only for convenience: all device directories are symlinks to `/sys/devices`.
+
+E.g.:
+
+    ls -l /sys/class/rtc/
+
+Gives the `rtc0` device directory:
+
+    total 0
+    lrwxrwxrwx 1 root root 0 Sep 25 09:46 rtc0 -> ../../devices/pnp0/00:02/rtc/rtc0
+
 ### Bibliography
 
 <http://prefetch.net/articles/linuxpci.html>

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +P1
 +# The image is 3 x 2.
 +3 2
 +0 1 0
 +1 0 1