一、简介
ddjvu是linux下处理djvu图片的常用命令，该命令不是linux自带的shell命令，需要额外进行安装之后才能够使用，ddjvu主要实现djvu图片的格式装换和切割等功能。convert命令的功能更加的强大，在linux中使用man convert来查看给命令时，它给出了这样的解释：
convert - convert between image formats as well as resize an image,
blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more.
足以说明其功能的多样性，是linux下处理图片的常用工具。
二、安装
1、ddjvu的安装
1) 下载djvulibre-x.x.x.x.tar.gz源码；
2) 使用tar命令解压上面下载的源码；
3) 进入解压后的目录，并运行 ./configure，如果成功则进行下一步，否则根据提示进行处理；
4) 运行make && make install 命令(或者分开运行)
注：安装完djvulibre之后我们可以发现，系统中增加了不止ddjvu一个命令，其他命令也有很大的用处，想djvudump命令可以方便的得到djvu图片的信息等，这些命令可以再需要的时候进行查看。
2、 convert的安装
在Redhat / Centos / Fedora中我们直接使用
yum install ImageMagick
而在ubuntu / Debian中我们可以使用
apt-get install ImageMagick
在ubuntu上如果发现存在依赖包的问题，可以使用下面安装命令：
aptitude install imagemagick
三、使用
ddjvu和convert命令的功能非常的强大，在这里直接将linux中的帮助文档贴在下面，以便查找相应的功能：
1、ddjvu
NAME
ddjvu - Command line DjVu decoder.
SYNOPSIS
ddjvu -format=fmt [options] [djvufile] [outputfile]
DESCRIPTION
Decode the DjVu file djvufile, produces the image file outputfile.
The DjVu data is read from the standard input when argument djvufile is not specified or when it is equal to a single dash. Similarly, the output data is written to the standard output when argument outputfile is not specified or equal to a single dash.
However a valid output file name is always required when producing a TIFF or PDF file.
MAIN OPTIONS
-format=fmt
Specify the output file formats. The recognized file formats are
pbm, pgm, ppm, pnm, rle, tiff, and pdf.
* Formats pbm, pgm, and ppm respectively produce a Portable Bitmap (PBM), Portable Graymap (PGM), or Portable Pixmap (PGM) file. Format pnm produces a PBM, PGM, or PPM output file according to the color content of the output image.
* Format rle produces a compact run length encoded bitonal file that is understood by the DjVuLibre commands cjb2 and csepdjvu.
* Format tiff produces a Tagged Image Format (TIFF) file. The resulting file uses the best available lossless compression model. Enabling lossy JPEG compression (see option -quality below) often produces much smaller files. Commands tiffcp(1)
and tiffsplit(1) are useful for manipulating the resulting TIFF files.
* Format pdf produces a Portable Document Format (PDF) file. Each page in the resulting file is represented by an image at the specified resolution, using the best available lossless compression model. Enabling lossy JPEG compression (see
option -quality below) often produces much smaller files. An alternate way to produce PDF file consists in first using djvups(1) and convert the resulting PostScript file to PDF. Which method gives better results depends on the contents of the DJVU file
and on the capabilities of the PS to PDF converter.
When option -format is not specified, the extension of argument outputfile has no influence on the default output format. Instead the program behavior is modified to ensure backward compatibility with previous versions of ddjvu. We recommend
to always specify the output format using this option.
-page=pagespec
Specify which pages should be decoded. When this option is not specified, all pages of the documents are decoded and concatenated into the output file. The page specification pagespec contains one or more comma-separated page ranges.A page
range is either a page number,or two page numbers separated by a dash. For instance, specification 1-10 outputs pages 1 to 10, and specification 1,3,99999-4 outputs pages 1 and 3, followed by all the document pages in reverse order up to page 4.
-mode=mod
Selects which layers of the DjVu image should be rendered. Valid rendering modes are color, black, mask, foreground, and background.
* Rendering mode color is the default mode. When the DjVu file is bitonal, bitonal or gray-level output is produced depending on the subsampling factor. Otherwise a color image is produced.
* Rendering mode black is useful to extract a meaningful black and white image. bitonal or gray-level output is produced depending on the subsampling factor.
* Rendering modes mask, foreground, and background select specific layers of a DjVu image. These modes can fail if the DjVu image does not contain the selected layer.
-skip Instead of aborting when encountering a corrupted page, this option causes ddjvu to simply skip the corrupted page and continue with the next. This is useful for processing certain damaged files.
RESOLUTION OPTIONS
The following options control the resolution of the output image. The default resolution is the native resolution of the DjVu file, equivalent to selecting -1.
-n Specify an integer sub-sampling factor. The dimensions of the full output image will be n times smaller than the DjVu image size. The legal values for argument n range from 1 to 12. Option -1, for instance, produces an output
image whose resolution is equal to the resolution of the input DjVu image file.
-subsample=n
This is equivalent to option -n.
-scale=mag
Specify a magnification factor relative to the resolution stored in the DjVu image. Specifying magnification of 100 produces an image suitable for displaying on a 100 dpi device such as a computer screen. The magnification factor mag can
also be interpreted as the resolution of the output image expressed in dot per inch.
-size=wxh
Specify the size of the full output image. Rendering the full DjVu image would create an output image whose width and height would not exceed w and h. To change the aspect ratio, you must also use option -aspect=no.
-aspect=yesno
This option indicates whether the image aspect ratio should be preserved. The defaults is to preserve the aspect ration. This option permits changes in the aspect ratio when used in combination with option -size.
OTHER OPTIONS
-verbose
Display informational messages describing the structure of the DjVu image and the format of the output file.
-segment=wxh+x+y
Specify an image segment to render. Program ddjvu conceptually renders the full page using the specified resolution, and then extracts a sub-image of width w and height h, starting at position (x,y) relative to the bottom left corner of the
page. Both operations of course happen simultaneously. Rendering a small sub-image is much faster than rendering the complete image. The output file will always have size wxh when this option is specified.
-quality=factor
Enables lossy compression in TIFF and PDF files. Without this option, TIFF or PDF output files always use lossless compression or no compression. Argument factor specifies a JPEG quantization factor ranging from 25 to 150. See command
cjpeg(1) for more information on JPEG quantization factors. Value 80 is a good starting point.
-quality=uncompressed
Completely disables compression in TIFF and PDF files. Although the resulting files are often huge, this is sometimes useful for maximal compatibility with hastily written software.
DEPRECATED OPTIONS
Various options have been maintained to ensure backward compatibility with previous versions of ddjvu. When option -format is not specified, the program only decodes the first page of the document and the default resolution becomes -scale=100.
Options -size, -scale, -segment, and -page accept an argument separated by a space. Options -foreground, -background, and -black are shorthands for the -mode=mod option. Please do not rely on these features.
EXAMPLES
Command: ddjvu -format=tiff myfile.djvu myfile.tif
decodes all pages and produces a multipage TIFF file.
Command: ddjvu -format=ppm -page=1 -size=100x100 myfile.djvu -
produces a thumbnail for the first page of a document and outputs it as a PPM file on the standard output.
2、convert
NAME
convert - convert between image formats as well as resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more.
SYNOPSIS
convert [input-options] input-file [output-options] output-file
OVERVIEW
The convert program is a member of the ImageMagick(1) suite of tools. Use it to convert between image formats as well as resize an image, blur, crop, despeckle,
dither, draw on, flip, join, re-sample, and much more.
DESCRIPTION
Image Settings:
-adjoin join images into a single multi-image file
-affine matrix affine transform matrix
-antialias remove pixel-aliasing
-authenticate value decrypt image with this password
-background color background color
-bias value add bias when convolving an image
-black-point-compensation use black point compensation
-blue-primary point chromaticity blue primary point
-bordercolor color border color
-caption string assign a caption to an image
-cdl filename color correct with a color decision list
-channel type apply option to select image channels
-colors value preferred number of colors in the image
-colorspace type alternate image colorspace
-comment string annotate image with comment
-compose operator set image composite operator
-compress type type of pixel compression when writing the image
-decipher filename convert cipher pixels to plain pixels
-define format:option define one or more image format options
-delay value display the next image after pausing
-density geometry horizontal and vertical density of the image
-depth value image depth
-display server get image or font from this X server
-dispose method layer disposal method
-dither method apply error diffusion to image
-encipher filename convert plain pixels to cipher pixels
-encoding type text encoding type
-endian type endianness (MSB or LSB) of the image
-family name render text with this font family
-fill color color to use when filling a graphic primitive
-filter type use this filter when resizing an image
-flatten flatten a sequence of images
-font name render text with this font
-format "string" output formatted image characteristics
-fuzz distance colors within this distance are considered equal
-gravity type horizontal and vertical text placement
-green-primary point chromaticity green primary point
-intent type type of rendering intent when managing the image color
-interlace type type of image interlacing scheme
-interpolate method pixel color interpolation method
-label string assign a label to an image
-limit type value pixel cache resource limit
-loop iterations add Netscape loop extension to your GIF animation
-mask filename associate a mask with the image
-matte store matte channel if the image has one
-mattecolor color frame color
-monitor monitor progress
-orient type image orientation
-origin geometry image origin
-page geometry size and location of an image canvas (setting)
-ping efficiently determine image attributes
-pointsize value font point size
-preview type image preview type
-quality value JPEG/MIFF/PNG compression level
-quiet suppress all warning messages
-red-primary point chromaticity red primary point
-regard-warnings pay attention to warning messages
-sampling-factor geometry horizontal and vertical sampling factor
-scene value image scene number
-seed value seed a new sequence of pseudo-random numbers
-size geometry width and height of image
-stretch type render text with this font stretch
-stroke color graphic primitive stroke color
-strokewidth value graphic primitive stroke width
-style type render text with this font style
-support factor resize support: > 1.0 is blurry, < 1.0 is sharp
-texture filename name of texture to tile onto the image background
-tile-offset geometry tile offset
-treedepth value color tree depth
-transparent-color color transparent color
-undercolor color annotation bounding box color
-units type the units of image resolution
-verbose print detailed information about the image
-view FlashPix viewing transforms
-virtual-pixel method virtual pixel access method
-weight type render text with this font weight
-white-point point chromaticity white point
Image Operators:
-adaptive-blur geometry adaptively blur pixels; decrease effect near edges
-adaptive-resize geometry adaptively resize image with data dependent triangulation
-adaptive-sharpen geometry adaptively sharpen pixels; increase effect near edges
-annotate geometry text annotate the image with text
-auto-orient automatically orient image
-black-threshold value force all pixels below the threshold into black
-blur geometry reduce image noise and reduce detail levels
-border geometry surround image with a border of color
-charcoal radius simulate a charcoal drawing
-chop geometry remove pixels from the image interior
-clip clip along the first path from the 8BIM profile
-clip-mask filename associate a clip mask with the image
-clip-path id clip along a named path from the 8BIM profile
-colorize value colorize the image with the fill color
-contrast enhance or reduce the image contrast
-contrast-stretch geometry improve contrast by `stretching' the intensity range
-convolve coefficients apply a convolution kernel to the image
-cycle amount cycle the image colormap
-despeckle reduce the speckles within an image
-draw string annotate the image with a graphic primitive
-edge radius apply a filter to detect edges in the image
-emboss radius emboss an image
-enhance apply a digital filter to enhance a noisy image
-equalize perform histogram equalization to an image
-evaluate operator value evaluate an arithmetic, relational, or logical expression
-extent geometry set the image size
-extract geometry extract area from image
-fft implements the discrete Fourier transform (DFT)
-flip flip image vertically
-floodfill geometry color floodfill the image with color
-flop flop image horizontally
-frame geometry surround image with an ornamental border
-function name apply a function to the image
-gamma value level of gamma correction
-gaussian-blur geometry reduce image noise and reduce detail levels
-geometry geometry preferred size or location of the image
-identify identify the format and characteristics of the image
-ift implements the inverse discrete Fourier transform (DFT)
-implode amount implode image pixels about the center
-lat geometry local adaptive thresholding
-layers method optimize or compare image layers
-level value adjust the level of image contrast
-linear-stretch geometry improve contrast by `stretching with saturation' the intensity range
-median radius apply a median filter to the image
-modulate value vary the brightness, saturation, and hue
-monochrome transform image to black and white
-morphology method kernel apply a morphology method to the image
-motion-blur geometry simulate motion blur
-negate replace each pixel with its complementary color
-noise radius add or reduce noise in an image
-normalize transform image to span the full range of colors
-opaque color change this color to the fill color
-ordered-dither NxN add a noise pattern to the image with specific amplitudes
-paint radius simulate an oil painting
-polaroid angle simulate a Polaroid picture
-posterize levels reduce the image to a limited number of color levels
-print string interpret string and print to console
-profile filename add, delete, or apply an image profile
-quantize colorspace reduce colors in this colorspace
-radial-blur angle radial blur the image
-raise value lighten/darken image edges to create a 3-D effect
-random-threshold low,high random threshold the image
-recolor matrix translate, scale, shear, or rotate image colors
-region geometry apply options to a portion of the image
-render render vector graphics
-repage geometry size and location of an image canvas
-resample geometry change the resolution of an image
-resize geometry resize the image
-roll geometry roll an image vertically or horizontally
-rotate degrees apply Paeth rotation to the image
-sample geometry scale image with pixel sampling
-scale geometry scale the image
-segment values segment an image
-selective-blur geometry selectively blur pixels within a contrast threshold
-sepia-tone threshold simulate a sepia-toned photo
-set property value set an image property
-shade degrees shade the image using a distant light source
-shadow geometry simulate an image shadow
-sharpen geometry sharpen the image
-shave geometry shave pixels from the image edges
-shear geometry slide one edge of the image along the X or Y axis
-sigmoidal-contrast geometry lightness rescaling using sigmoidal contrast enhancement
-sketch geometry simulate a pencil sketch
-solarize threshold negate all pixels above the threshold level
-splice geometry splice the background color into the image
-spread amount displace image pixels by a random amount
-strip strip image of all profiles and comments
-swirl degrees swirl image pixels about the center
-threshold value threshold the image
-thumbnail geometry create a thumbnail of the image
-tile filename tile image when filling a graphic primitive
-tint value tint the image with the fill color
-transform affine transform image
-transparent color make this color transparent within the image
-transpose flip image vertically and rotate 90 degrees
-transverse flop image horizontally and rotate 270 degrees
-trim trim image edges
-type type image type
-unique-colors discard all but one of any pixel color
-unsharp geometry sharpen the image
-vignette geometry soften the edges of the image in vignette style
-wave geometry alter an image along a sine wave
-white-threshold value force all pixels above the threshold into white
Image Sequence Operators:
-affinity filename transform image colors to match this set of colors
-append append an image sequence
-clut apply a color lookup table to the image
-coalesce merge a sequence of images
-combine combine a sequence of images
-composite composite image
-crop geometry cut out a rectangular region of the image
-deconstruct break down an image sequence into constituent parts
-evaluate-sequence operator evaluate an arithmetic, relational, or logical expression
-flatten flatten a sequence of images
-fx expression apply mathematical expression to an image channel(s)
-hald-clut apply a Hald color lookup table to the image
-morph value morph an image sequence
-mosaic create a mosaic from an image sequence
-process arguments process the image with a custom image filter
-separate separate an image channel into a grayscale image
-write filename write images to this file
Image Stack Operators:
-clone index clone an image
-delete index delete the image from the image sequence
-insert index insert last image into the image sequence
-swap indexes swap two images in the image sequence
Miscellaneous Options:
-debug events display copious debugging information
-help print program options
-log format format of debugging information
-list type print a list of supported option arguments
-version print version information
By default, the image format of `file' is determined by its magic number. To specify a particular image format, precede the filename with an image format name and a colon (i.e. ps:image) or specify the image type as the filename suffix (i.e. image.ps).
Specify 'file' as '-' for standard input or output.