Octave 无法使用 GraphicsMagick 读取文件

Question

我正在尝试在 OS X 上使用 GraphicsMagick 1.3.27（通过 brew）在 Octave 4.2.1 中加载图像。这是错误：

>> img = imread('./myimg.jpg')
error: Magick++ exception: octave-cli-4.2: No decode delegate for this 
image format (<path to myimg.jpg>) reported by magick/constitute.c:1535 (ReadImage)
 error: called from
    __imread__ at line 80 column 10
    imageIO at line 117 column 26
    imread at line 106 column 30

GraphicsMagick 看起来配置正确：

 gm -version
 GraphicsMagick 1.3.27  Q16 http://www.GraphicsMagick.org/
 Copyright (C) 2002-2017 GraphicsMagick Group.
 Additional copyrights and licenses apply to this software.
 See http://www.GraphicsMagick.org/www/Copyright.html for details.

 Feature Support:
   Native Thread Safe       yes
   Large Files (> 32 bit)   yes
   Large Memory (> 32 bit)  yes
   BZIP                     yes
   DPS                      no
   FlashPix                 no
   FreeType                 yes
   Ghostscript (Library)    no
   JBIG                     no
   JPEG-2000                no
   JPEG                     yes
   Little CMS               no
   Loadable Modules         yes
   OpenMP                   no
   PNG                      yes
   TIFF                     yes
   TRIO                     no
   UMEM                     no
   WebP                     no
   WMF                      no
   X11                      no
   XML                      no
   ZLIB                     yes

 Host type: x86_64-apple-darwin16.7.0

 Configured using the command:
   ./configure  '--prefix=/usr/local/Cellar/graphicsmagick/1.3.27' '-- 
disable-dependency-tracking' '--enable-shared' '--disable-static' '--with-modules' '--without-lzma' '--disable-openmp' '--with-quantum-depth=16' '--disable-installed' '--without-gslib' '--with-gs-font-dir=/usr/local/share/ghostscript/fonts' '--without-x' '--without-lcms2' 'CC=clang' 'CXX=clang++'

 Final Build Parameters:
   CC       = clang
   CFLAGS   = -g -O2 -Wall -D_THREAD_SAFE
   CPPFLAGS = -I/usr/local/opt/freetype/include/freetype2
   CXX      = clang++
   CXXFLAGS = -D_THREAD_SAFE
   LDFLAGS  = -L/usr/local/opt/freetype/lib
   LIBS     = -lfreetype -lbz2 -lz -lltdl -lm -lpthread

尝试加载 png 文件导致同样的错误。直接从命令行使用 gm 效果很好。

Answer 1

您的 Octave 和 gm 安装可能链接到不同的 GraphicsMagick 库，因此 gm -version 的输出可能不准确。您可能应该从 Octave 内部检查它，如下所示：

octave:1> imformats 
Extension | isa | Info | Read | Write | Alpha | Description
----------+-----+------+------+-------+-------+------------
bmp       | yes | yes  | yes  | yes   | yes   | Microsoft Windows bitmap image
cur       | yes | yes  | yes  | no    | yes   | Microsoft Cursor Icon
gif       | yes | yes  | yes  | yes   | yes   | CompuServe graphics interchange format
ico       | yes | yes  | yes  | no    | yes   | Microsoft Icon
jbg       | yes | yes  | yes  | yes   | yes   | Joint Bi-level Image experts Group interchange format
jbig      | yes | yes  | yes  | yes   | yes   | Joint Bi-level Image experts Group interchange format
jpg, jpeg | yes | yes  | yes  | yes   | yes   | Joint Photographic Experts Group JFIF format
pbm       | yes | yes  | yes  | yes   | yes   | Portable bitmap format (black/white)
pcx       | yes | yes  | yes  | yes   | yes   | ZSoft IBM PC Paintbrush
pgm       | yes | yes  | yes  | yes   | yes   | Portable graymap format (gray scale)
png       | yes | yes  | yes  | yes   | yes   | Portable Network Graphics
pnm       | yes | yes  | yes  | yes   | yes   | Portable anymap
ppm       | yes | yes  | yes  | yes   | yes   | Portable pixmap format (color)
ras       | yes | yes  | yes  | yes   | yes   | SUN Rasterfile
tga, tpic | yes | yes  | yes  | yes   | yes   | Truevision Targa image
tif, tiff | yes | yes  | yes  | yes   | yes   | Tagged Image File Format
xbm       | yes | yes  | yes  | yes   | yes   | X Windows system bitmap (black/white)
xpm       | yes | yes  | yes  | yes   | yes   | X Windows system pixmap (color)
xwd       | yes | yes  | yes  | yes   | yes   | X Windows system window dump (color)

您还可以通过 ldd 检查 Octave 实际使用的库是什么（因为您使用的是 Mac，您可能没有 ldd 但 google 告诉我 otool -L 是 Mac 解决方案）。就我而言，我知道它们是相同的：

$ ldd /usr/local/lib/octave/5.0.0/liboctinterp.so | grep Magick
    libGraphicsMagick++-Q16.so.12 => /lib/libGraphicsMagick++-Q16.so.12 (0x00007f858a896000)
    libGraphicsMagick-Q16.so.3 => /lib/libGraphicsMagick-Q16.so.3 (0x00007f858a52e000)
$ ldd /usr/bin/gm | grep Magick
    libGraphicsMagick-Q16.so.3 => /lib/libGraphicsMagick-Q16.so.3 (0x00007f5041f66000)

一旦您知道 Octave 为 GraphicsMagick 使用的实际库，您就可以检查该库是否链接到 libjpeg：

$ ldd /lib/libGraphicsMagick++-Q16.so.12 | grep jpeg
    libjpeg.so.62 => /lib/x86_64-linux-gnu/libjpeg.so.62 (0x00007f63e910c000)

您也可以从八度配置中获得一些提示：

octave:1> __octave_config_info__.build_environment.MAGICK_CPPFLAGS
ans = -I/usr/include/GraphicsMagick
octave:2> __octave_config_info__.build_environment.MAGICK_LDFLAGS
ans = 
octave:3> __octave_config_info__.build_environment.MAGICK_LIBS
ans = -lGraphicsMagick++ -lGraphicsMagick

Octave 无法使用 GraphicsMagick 读取文件

Octave can't read file using GraphicsMagick

octave

graphicsmagick