April 24th, 2011 by usage | Filed under General, Linux/Unix, Mac OS, Operating Systems

convertĀ  – convert between image formats as well as resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more.

How to resize image to 800px wide

convert -resize 800 -quality 80% source.jpg target_w800.jpg


$ convert --help
Version: ImageMagick 6.2.4 10/02/07 Q16
Copyright: Copyright (C) 1999-2005 ImageMagick Studio LLC

Usage: convert [options ...] file [ [options ...] file ...] [options ...] file

Where options include:
  -adjoin              join images into a single multi-image file
  -affine matrix       affine transform matrix
  -annotate geometry text
                       annotate the image with text
  -antialias           remove pixel-aliasing
  -append              append an image sequence
  -authenticate value  decrypt image with this password
  -average             average an image sequence
  -background color    background color
  -bias value          add bias when convolving an image
  -black-threshold value
                       forces all pixels below the threshold into black
  -blue-primary point  chromaticity blue primary point
  -blur geometry       blur the image
  -border geometry     surround image with a border of color
  -bordercolor color   border color
  -channel type        apply option to select image channels
  -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-path id        clip along a named path from the 8BIM profile
  -clone index         clone an image
  -coalesce            merge a sequence of images
  -colorize value      colorize the image with the fill color
  -colors value        preferred number of colors in the image
  -colorspace type     alternate image colorspace
  -combine             combine a sequence of images
  -comment string      annotate image with comment
  -compose operator    set image composite operator
  -composite           composite image
  -compress type       type of pixel compression when writing the image
  -contrast            enhance or reduce the image contrast
  -convolve coefficients
                       apply a convolution kernel to the image
  -crop geometry       cut out a rectangular region of the image
  -cycle amount        cycle the image colormap
  -debug events        display copious debugging information
  -define format:option
                       define one or more image format options
  -deconstruct         break down an image sequence into constituent parts
  -delay value         display the next image after pausing
  -delete index        delete the image from the image sequence
  -density geometry    horizontal and vertical density of the image
  -depth value         image depth
  -despeckle           reduce the speckles within an image
  -display server      get image or font from this X server
  -dispose method      GIF disposal method
  -dither              apply Floyd/Steinberg error diffusion to 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
  -encoding type       text encoding type
  -endian type         endianness (MSB or LSB) of the 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
  -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
  -flip                flip image in the vertical direction
  -floodfill geometry color
                       floodfill the image with color
  -flop                flop image in the horizontal direction
  -font name           render text with this font
  -format "string"     output formatted image characteristics
  -frame geometry      surround image with an ornamental border
  -fuzz distance       colors within this distance are considered equal
  -fx expression       apply mathematical expression to an image channel(s)
  -gamma value         level of gamma correction
  -gaussian geometry   gaussian blur an image
  -geometry geometry   perferred size or location of the image
  -green-primary point chromaticity green primary point
  -gravity type        horizontal and vertical text placement
  -help                print program options
  -implode amount      implode image pixels about the center
  -insert index        insert last image into the image sequence
  -intent type         type of rendering intent when managing the image color
  -interlace type      type of image interlacing scheme
  -label name          assign a label to an image
  -lat geometry        local adaptive thresholding
  -level value         adjust the level of image contrast
  -limit type value    pixel cache resource limit
  -log format          format of debugging information
  -loop iterations     add Netscape loop extension to your GIF animation
  -map filename        transform image colors to match this set of colors
  -mask filename       set the image clip mask
  -matte               store matte channel if the image has one
  -mattecolor color    frame color
  -median radius       apply a median filter to the image
  -modulate value      vary the brightness, saturation, and hue
  -monitor             monitor progress
  -monochrome          transform image to black and white
  -morph value         morph an image sequence
  -mosaic              create a mosaic from an image sequence
  -motion-blur geometry
                       simulate motion blur
  -negate              replace every 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
                       ordered dither the image
  -orient type         image orientation
  -page geometry       size and location of an image canvas (setting)
  -paint radius        simulate an oil painting
  -ping                efficiently determine image attributes
  -pointsize value     font point size
  -posterize levels    reduce the image to a limited number of color levels
  -preview type        image preview type
  -profile filename    add, delete, or apply an image profile
  -quality value       JPEG/MIFF/PNG compression level
  -quiet               suppress all error or warning messages
  -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
  -region geometry     apply options to a portion of the image
  -raise value         lighten/darken image edges to create a 3-D effect
  -red-primary point   chromaticity red primary point
  -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
  -sampling-factor geometry
                       horizontal and vertical sampling factor
  -scale geometry      scale the image
  -scene value         image scene number
  -seed value          pseudo-random number generator seed value
  -segment values      segment an image
  -separate            separate an image channel into a grayscale image
  -sepia-tone threshold
                       simulate a sepia-toned photo
  -set attribute value set an image attribute
  -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
  -sigmodial-contrast geometry
                       lightness rescaling using sigmoidal contrast enhancement
  -size geometry       width and height of image
  -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
  -stroke color        graphic primitive stroke color
  -strokewidth value   graphic primitive stroke width
  -stretch type        render text with this font stretch
  -style type          render text with this font style
  -support factor      resize support: > 1.0 is blurry, < 1.0 is sharp
  -swap indexes        swap two images in the image sequence
  -swirl degrees       swirl image pixels about the center
  -texture filename    name of texture to tile onto the image background
  -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
  -treedepth value     color tree depth
  -trim                trim image edges
  -type type           image type
  -undercolor color    annotation bounding box color
  -units type          the units of image resolution
  -unsharp geometry    sharpen the image
  -verbose             print detailed information about the image
  -version             print version information
  -view                FlashPix viewing transforms
  -virtual-pixel method
                       virtual pixel access method
  -wave geometry       alter an image along a sine wave
  -weight type         render text with this font weight
  -white-point point   chromaticity white point
  -white-threshold value
                       forces all pixels above the threshold into white
  -write filename      write images to this file

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.  Specify 'file' as
'-' for standard input or output.


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