用Java的ImageIO处理一个大于15M的JPG文件，内存溢出。
于是寻求新的解决方案，用ImageMagicK，发现处理图片速度不令人满意，于是切换至GraphicsMagicK,如下是总结。
“GraphicsMagick is a fork of ImageMagick. GraphicsMagick has a number of advantages compared to ImageMagick, the most prominent is it's superior performance.” -from im4java development guide.
如下是快速的总结：
GraphicsMagick（gm)是ImageMagick（im）派生出来的，性能好。
gm和im都需要安装依赖的库，才能处理如jpeg，png图片。
依赖的库有：zlib-1.2.8.tar.gz;libpng-1.6.23.tar.gz;jpegsrc.v9b.tar.gz, 需要首先安装。
ImageMagick安装直接可以用yum安装，如 list|grep -i imagemagick
GraphicsMagick安装需要本地编译安装，首先执行./configure 看看最后有没有png, jpeg, zlib.(重要）
GraphicsMagick与ImageMagick的安装相互独立，但依赖的包相同。
性能上，15Mjpg文件resize，gm快~20%（4U, 4G), 而在一台性能较差的虚拟机gm要比im快6倍（2U，1G），
图片越大，resize的尺寸越大，性能差别越明显。机器配置相差越大，性能差别越大。
性能测试对比
在一台2U1G VirtualBox Linux下resize一个15M的jpg图片。分别用gm和im进行操作，然后对比。
[root@testserver image]# uname -a
Linux testserver 2.6.32-431.el6.i686 #1 SMP Fri Nov 22 00:26:36 UTC 2013 i686 i686 i386 GNU/Linux
[root@testserver image]# free -m
total used free shared buffers cached
Mem: 1178 458 719 0 17 302
-/+ buffers/cache: 138 1039
Swap: 2015 137 1878
[root@testserver image]# gm identify test-bigjpg.jpg
test-bigjpg.jpg JPEG 9864x13703+0+0 DirectClass 8-bit 14.8Mi 0.000u 0:01
resize 操作对比：
[root@testserver image]# ./test.sh test-bigjpg.jpg 2048
elapsed 25s using gm
elapsed 154s using im
Identify -verbose 操作对比：
[root@testserver image]# identify -verbose 1464755573477_45.jpg
Image: 1464755573477_45.jpg
Format: JPEG (Joint Photographic Experts Group JFIF format)
Class: DirectClass
Geometry: 13925x6459+0+0
Resolution: 200x200
Print size: 69.625x32.295
Units: PixelsPerInch
Type: ColorSeparation
Endianess: Undefined
Colorspace: CMYK
Depth: 8-bit
.....//此处省略
User time: 5.940u
Elapsed time: 0:34.689
Version: ImageMagick 6.7.2-7 2016-05-09 Q16 http://www.imagemagick.org
[root@testserver image]# gm identify -verbose 1464755573477_45.jpg
Image: 1464755573477_45.jpg
Format: JPEG (Joint Photographic Experts Group JFIF format)
Geometry: 13925x6459
Class: DirectClass
Type: color separated
Depth: 8 bits-per-pixel component
... //此处省略
User Time: 6.580u
Elapsed Time: 0:08
Pixels Per Second: 11.8Mi
附上测试脚本的代码：
#!/bin/sh
starttime=`date '+%s'`
gm convert $1 -resize $2 $1.resize$2.jpg
stoptime=`date '+%s'`
echo elapsed `expr $stoptime - $starttime`s using gm starttime=`date '+%s'`
convert $1 -resize $2 $1.resize$2.jpg
stoptime=`date '+%s'`
echo elapsed `expr $stoptime - $starttime`s using im
Im4java
Im4java同时支持GM 和 IM
With im4java, you have three options if you want to use GraphicsMagick:
- use GraphicsMagick explicitely, passing the command at object-creation: GraphicsMagickCmd cmd = new GraphicsMagickCmd("convert");.
- use GraphicsMagick explicitely, using wrapper classes: ConvertCmd cmd = new ConvertCmd(true);.
- decide at runtime: setting the system-property im4java.useGM to true will select GraphicsMagick at runtime. You can use this feature to compare the results and timings of both toolsets, provided that the commandline is compatible.
Reference:
GraphicsMagick: http://www.graphicsmagick.org/
ImageMagick:http://www.imagemagick.org/script/index.php
Delegatge lib: ftp://ftp.graphicsmagick.org/pub/GraphicsMagick/delegates/