ImageMagickのソースを表示

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[[Wikipedia:ImageMagick|Wikipedia]] から:

:ImageMagick は、ラスターイメージファイルとベクターイメージファイルを表示、変換、編集するための無料のオープンソースソフトウェアスイートです。200 を超える画像ファイル形式を読み書きできます。

== インストール ==

{{Pkg|imagemagick}} パッケージを [[インストール]] します。あるいは、API とコマンドラインインターフェイスの安定性を重視した ImageMagick のフォークである [[Wikipedia:GraphicsMagick|GraphicsMagick]] の {{Pkg|graphicsmagick}} をインストールします。

== Usage ==

See {{man|1|ImageMagick}}, or {{man|1|gm}} for GraphicsMagick.

{{Tip|The official HTML documentation is available locally when the packages are installed:
* ImageMagick at {{ic|/usr/share/doc/ImageMagick-7/www/index.html}}
* GraphicsMagick at {{ic|/usr/share/doc/GraphicsMagick/www/index.html}}}}

=== Common operations ===

{{Note|The sign before an option is important. Opposite operations can be performed by using a ''plus'' instead of a ''minus''.}}

==== Convert between image formats ====

The basic usage of this facility is to specify the existing, and desired, image formats as the filename extension. For example, to get the ''.jpg'' representation of a given ''.png'' image, use: 

 $ convert image.png image.jpg

==== Append ====

Combining multiple pictures into one:

 $ convert -append ''input.pngs'' ''output.png''

==== Crop, chop ====

To crop part of multiple images and convert them to another format:

 $ mogrify -crop ''WIDTH''x''HEIGHT''+''X''+''Y'' -format jpg *.png

Where ''WIDTH'' and ''HEIGHT'' is the cropped output image size, and ''X'' and ''Y'' is the offset from the input image size.

One can also {{ic|-chop}} to cut of a single edge from an image, using gravity to select that edge. Which is easier as less numbers, or trial and error, is involved.

 $ magick frame_red.gif -gravity South -chop 0x10 chop_bottom.gif

==== Limit the storage size ====

To achieve reasonable quality for a given storage size:

 $ convert image.jpg -define jpeg:extent=3000KB image_small.jpg

Hopefully, this will shorten the transmission time. Note that {{ic|-quality}}, as in 

 $ convert image.jpg -quality 85% image_small.jpg

is harder to use when the correlation between quality and storage size is not clear.

=== Screenshot taking ===

An easy way to take a screenshot of your current system is using the {{man|1|import}} command:

 $ import -window root screenshot.jpg

Running {{ic|import}} without the {{ic|-window}} option allows selecting a window or an arbitrary region interactively. With {{ic|-pause}} you can specify a delay in which you can, for example, lower some windows. 

{{Note|If you prefer '''graphicsmagick''' alternative, just prepend "gm", e.g. {{ic|$ gm import -window root screenshot.jpg}}.}}

==== Screenshot of multiple X screens ====

If you run twinview or dualhead, simply take the screenshot twice and use {{ic|imagemagick}} to paste them together:

{{bc|
$ import -window root -display :0.0 -screen /tmp/0.png
$ import -window root -display :0.1 -screen /tmp/1.png
$ convert +append /tmp/0.png /tmp/1.png screenshot.png
$ rm /tmp/{0,1}.png
}}

==== Screenshot of individual Xinerama heads ====

Xinerama-based multi-head setups have only one virtual screen. If the physical screens are different in height, you will find dead space in the screenshot. In this case, you may want to take screenshot of each physical screen individually. As long as Xinerama information is available from the X server, the following will work:

{{bc|<nowiki>
#!/bin/sh
xdpyinfo -ext XINERAMA | sed '/^  head #/!d;s///' |
while IFS=' :x@,' read i w h x y; do
        import -window root -crop ${w}x$h+$x+$y head_$i.png
done
</nowiki>}}

==== Screenshot of the active/focused window ====

The following script takes a screenshot of the currently focused window. It works with EWMH/NetWM compatible X Window Managers. To avoid overwriting previous screenshots, the current date is used as the filename.

{{bc|<nowiki>
#!/bin/sh
activeWinLine=$(xprop -root | grep "_NET_ACTIVE_WINDOW(WINDOW)")
activeWinId=${activeWinLine:40}
import -window "$activeWinId" /tmp/$(date +%F_%H%M%S_%N).png
</nowiki>}}

Alternatively, the following should work regardless of EWMH support:

 $ import -window "$(xdotool getwindowfocus -f)" /tmp/$(date +%F_%H%M%S_%N).png

{{Note|If screenshots of some programs (e.g. [[zathura]]) appear blank, try appending {{ic|-frame}} or removing {{ic|-f}} from the {{ic|xdotool}} command.}}

=== Encryption of image data ===

To encrypt:

 $ echo ''pass_phrase'' | magick ''image.jpg'' -encipher - -depth 8 png24:''image.png''

This can be decrypted by:

 $ echo ''pass_phrase'' | magick ''image.png'' -decipher - ''image.jpg''

It is highly advised to read the discussion at [https://imagemagick.org/Usage/transform/#encipher Encrypting Images] for all sorts of issues, and suggestions, for such commands.

Metadata of image formats that have the {{ic|cipher}} tag can be used to test for encryption. However, it could be removed or spoofed by an EXIF editing program.

 $ identify -verbose image.png

In general, testing if a raster image was encrypted can be done by checking the distribution of the pixel components. If it exceeds a certain threshold, the data could be considered random and a possible candidate for encryption. However, an example for false positives are images created with the  [[wikipedia:Diamond-square algorithm|Diamond-square algorithm]].

== See also ==

* [https://www.imagemagick.org/ ImageMagick website] for an extensive list of options, [https://imagemagick.org/Usage/ examples] and [https://imagemagick.org/script/examples.php showcase].
* [[List of applications/Multimedia#Image processing]]
* [http://www.fmwconcepts.com/imagemagick/index.php Fred's ImageMagick Scripts] for large collection of ImageMagic scripts