Link to C++ Cheat, split imagemagick.

Author: cirosantilli

README.md

@@ -97,7 +97,8 @@ Other tools:
 
 Related subjects in other repositories:
 
-- [networking](https://github.com/cirosantilli/net): networking tools and protocols: HTTP, SSH, curl Apache.
+- [C++ Cheat](https://github.com/cirosantilli/cpp-cheat): contains some compilation / language heavy subjects like the POSIX C API or generation of dynamic libraries.
+- [Networking Cheat](https://github.com/cirosantilli/networking-tutorial): networking tools and protocols: HTTP, SSH, curl Apache.
 
 ##How to search for keywords
 

image/README.md

@@ -172,129 +172,7 @@ And changing the width was not working for me:
 
 #Utilities
 
-##ImageMagick
-
-Tons of image conversion tools.
-
-CLI + APIs in lots of languages, including C (native), C++ and Python.
-
-Reading the manual is a great image manipulation course.
-
-###identify
-
-Get info on ImageMagick on given image file and file formats supported by ImageMagick.
-
-List supported formats:
-
-    identify -list format
-
-Get size of an image:
-
-    identify -format "%[fx:w]x%[fx:h]" a.jpg
-
-###convert
-
-- process images
-- converts between formats
-- input/output format can be deduced automatically (from extension/magic)
-
-Does not do:
-
-- DJVU
-
-####GIF operations
-
-GIF to several images:
-
-    convert a.gif a.png
-
-Generates `a-N.png` images.
-
-Several images to GIF loop forever:
-
-    convert -delay 100 img*.png img.gif
-
-or:
-
-    convert -delay 100 -loop 0 img*.png img.gif
-
-Loop once and stop
-
-    convert -delay 100 -loop 1 img*.png img.gif
-
-####resize
-
-Resize to 50% or original size:
-
-	convert large.png -resize 50% small.png
-
-This:
-
-- takes averages between pixels to make image have less pixels
-- keeps bit depth
-
-Therefore, the image file size will be just a bit more than 1/4 of the original because:
-
-- 1/2 x 1/2 = 1/4 of the number of pixels
-- the PNG metadata size is unchanged, so this is not divided by 4.
-
-Resize to fixed width of 100 px, height maintains original proportion:
-
-	convert large.png -resize 100x small.png
-
-####crop
-
-`10x10`: rectangle to keep:
-
-        convert -crop 10x10 a.jpg b.jpg
-
-`+10+10`: top left corner of rectangle
-
-        convert -crop 10x10+10+10 a.jpg b.jpg
-
-top 50 percent:
-
-        convert -crop 100x50% a.jpg b.jpg
-
-cannot give top left corner in percentage
-
-bottom 50 percent:
-
-        convert -gravity south -crop 100x50% a.jpg b.jpg
-
-####color
-
-- `-colorspace Gray`: convert to grayscale:
-
-        convert in.png -colorspace Gray out.png
-
-- `-monochrome`: monochrome image. TODO == -depth 1? But not in my tests.
-
-- `-depth`: number of bits per pixel.
-
-- `-density`: PDFs are fixed width for printers, not pixel data, so you have to say how many DPI you want to take 300 makes output quite readable
-
-    Always set this for PDFs.
-
-    PDF to one JPG per page:
-
-        convert -density 300 a.pdf a.jpg
-
-- `-threshold`: Simple way to convert to black and white: if color average is above threshold, pixel is white else pixel is black:
-
-        convert -threshold 50 a.jpg b.jpg
-
-- `-level`: linear transform on color space:
-
-        convert -level -100,100 a.jpg b.jpg
-
-###animate
-
-Animate multiple images interactively:
-
-    animate -delay 100 img*.png
-
-Not meant to generate a GIF from the command line, but good choice to preview a GIF before creating one.
+[ImageMagick](imagemagick.md)
 
 ##ExactImage
 

image/imagemagick.md

@@ -0,0 +1,133 @@
+#ImageMagick
+
+Tons of image conversion tools.
+
+CLI + APIs in lots of languages, including C (native), C++ and Python.
+
+Reading the manual is a great image manipulation course.
+
+Man pages are very shallow: have a look at the online docs instead:
+
+- <http://www.imagemagick.org/script/command-line-options.php>
+
+##identify
+
+Get info on ImageMagick on given image file and file formats supported by ImageMagick.
+
+List supported formats:
+
+    identify -list format
+
+Get size of an image:
+
+    identify -format "%[fx:w]x%[fx:h]" a.jpg
+
+##convert
+
+- process images
+- converts between formats
+- input/output format can be deduced automatically (from extension/magic)
+
+Does not do:
+
+- DJVU
+
+###resize
+
+Resize to 50% or original size:
+
+	convert large.png -resize 50% small.png
+
+This:
+
+- takes averages between pixels to make image have less pixels
+- keeps bit depth
+
+Therefore, the image file size will be just a bit more than 1/4 of the original because:
+
+- 1/2 x 1/2 = 1/4 of the number of pixels
+- the PNG metadata size is unchanged, so this is not divided by 4.
+
+Resize to fixed width of 100 px, height maintains original proportion:
+
+	convert large.png -resize 100x small.png
+
+###crop
+
+`10x10`: rectangle to keep:
+
+        convert -crop 10x10 a.jpg b.jpg
+
+`+10+10`: top left corner of rectangle
+
+    convert -crop 10x10+10+10 a.jpg b.jpg
+
+Top 50 percent:
+
+    convert -crop 100x50% a.jpg b.jpg
+
+Cannot give top left corner in percentage
+
+Bottom 50 percent:
+
+        convert -gravity south -crop 100x50% a.jpg b.jpg
+
+###color
+
+-   `-colorspace Gray`: convert to grayscale:
+
+        convert in.png -colorspace Gray out.png
+
+-   `-monochrome`: monochrome image. TODO == -depth 1? But not in my tests.
+
+-   `-depth`: number of bits per pixel.
+
+-   `-density`: PDFs are fixed width for printers, not pixel data, so you have to say how many DPI you want to take 300 makes output quite readable
+
+    Always set this for PDFs.
+
+    PDF to one JPG per page:
+
+        convert -density 300 a.pdf a.jpg
+
+-   `-threshold`: Simple way to convert to black and white: if color average is above threshold, pixel is white else pixel is black:
+
+        convert -threshold 50 a.jpg b.jpg
+
+-   `-level`: linear transform on color space:
+
+        convert -level -100,100 a.jpg b.jpg
+
+###Transparency to white
+
+<http://stackoverflow.com/questions/2322750/replace-transparency-in-png-images-with-white-background>
+
+    convert image.png -background white -alpha remove white.png
+
+###GIF operations
+
+GIF to several images:
+
+    convert a.gif a.png
+
+Generates `a-N.png` images.
+
+Several images to GIF loop forever:
+
+    convert -delay 100 img*.png img.gif
+
+or:
+
+    convert -delay 100 -loop 0 img*.png img.gif
+
+Loop once and stop
+
+    convert -delay 100 -loop 1 img*.png img.gif
+
+##animate
+
+Animate multiple images interactively:
+
+    animate -delay 100 img*.png
+
+Not meant to generate a GIF from the command line, but good choice to preview a GIF before creating one.