Use the mogrify program to resize an image, blur, crop, despeckle, dither, draw on, flip, join, re-sample, and much more. This tool is similar to convert except that the original image file is overwritten (unless you change the file suffix with the -format option) with any changes you request. See Command Line Processing for advice on how to structure your mogrify command or see below for sample usages of the command.
Convert all our PNG images in a folder to the gif format:
# mogrify -format gif *.png
To reduce the size:
# mogrify -resize 50% rose.jpg
You can resize all your JPEG images in a folder to a maximum dimension of 256x256 with this command:
# mogrify -resize 256x256 *.jpg
You can find additional examples of using mogrify in Graphics from the Command Line. Further discussion is available in More Graphics from the Command Line and Examples of ImageMagick Usage.
The mogrify command recognizes these options. Click on an option to get more details about how that option works.
Option Description -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 -adjoin join images into a single multi-image file -affine matrix affine transform matrix -alpha on, activate, off, deactivate, set, opaque, copy", transparent, extract, background, or shape the alpha channel -annotate geometry text annotate the image with text -antialias remove pixel-aliasing -append append an image sequence -authenticate value decipher image with this password -auto-gamma automagically adjust gamma level of image -auto-level automagically adjust color levels of image -auto-orient automagically orient image -background color background color -bench iterations measure performance -bias value add bias when convolving an image -black-threshold value force all pixels below the threshold into black -blue-primary point chromaticity blue primary point -blue-shift factor simulate a scene at nighttime in the moonlight -blur geometry reduce image noise and reduce detail levels -border geometry surround image with a border of color -bordercolor color border color -brightness-contrast geometry improve brightness / contrast of the image -canny geometry use a multi-stage algorithm to detect a wide range of edges in the image -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 -charcoal radius simulate a charcoal drawing -chop geometry remove pixels from the image interior -clip clip along the first path from the 8BIM profile -clamp set each pixel whose value is below zero to zero and any the pixel whose value is above the quantum range to the quantum range (e.g. 65535) otherwise the pixel value remains unchanged. -clip-mask filename associate clip mask with the image -clip-path id clip along a named path from the 8BIM profile -clut apply a color lookup table to the image -complexoperator perform complex mathematics on an image sequence -connected-components connectivity connected-components uniquely labeled, choose from 4 or 8 way connectivity -contrast-stretch geometry improve the contrast in an image by `stretching' the range of intensity value -coalesce merge a sequence of images -colorize value colorize the image with the fill color -color-matrix matrix apply color correction to the image. -colors value preferred number of colors in the image -colorspace type set 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 image compression type -contrast enhance or reduce the image contrast -convolve coefficients apply a convolution kernel to the image -copy geometry offset copy pixels from one area of an image to another -crop geometry crop the image -cycle amount cycle the image colormap -decipher filename convert cipher pixels to plain -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 -direction type render text right-to-left or left-to-right -display server get image or font from this X server -dispose method layer disposal method -distort type coefficients distort image -distribute-cache port launch a pixel cache server -dither method apply error diffusion to image -draw string annotate the image with a graphic primitive -duplicate count,indexes duplicate an image one or more times -edge radius apply a filter to detect edges in the image -emboss radius emboss an image -encipher filename convert plain pixels to cipher pixels -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 -evaluate-sequence operator evaluate an arithmetic, relational, or logical expression for an image sequence -extent geometry set the image size -extract geometry extract area from image -family name render text with this font family -features distance analyze image features (e.g. contract, correlations, etc.). -fft implements the discrete Fourier transform (DFT) -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 type output formatted image characteristics -frame geometry surround image with an ornamental border -function name apply a function to the image -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-blur geometry reduce image noise and reduce detail levels -geometry geometry preferred size or location of the image -gravity type horizontal and vertical text placement -grayscale method convert image to grayscale -green-primary point chromaticity green primary point -help print program options -hough-lines geometry identify lines in the image -identify identify the format and characteristics of the image -ifft implements the inverse discrete Fourier transform (DFT) -implode amount implode image pixels about the center -insert index insert last image into the image sequence -intensity method method to generate an intensity value from a pixel -intent type type of rendering intent when managing the image color -interlace type type of image interlacing scheme -interline-spacing value the space between two text lines -interpolate method pixel color interpolation method -interword-spacing value the space between two words -kerning value the space between two characters -kuwahara geometry edge preserving noise reduction filter -label string assign a label to an image -lat geometry local adaptive thresholding -layers method optimize or compare image layers -level value adjust the level of image contrast -limit type value pixel cache resource limit -linear-stretch geometry linear with saturation histogram stretch -liquid-rescale geometry rescale image with seam-carving -log format format of debugging information -loop iterations add Netscape loop extension to your GIF animation -mask filename associate a mask with the image -mattecolor color frame color -median radius apply a median filter to the image -mean-shift geometry delineate arbitrarily shaped clusters in the image -metric type measure differences between images with this metric -mode radius make each pixel the 'predominant color' of the neighborhood -modulate value vary the brightness, saturation, and hue -monitor monitor progress -monochrome transform image to black and white -morph value morph an image sequence -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 ordered dither the image -orient type image orientation -page geometry size and location of an image canvas (setting) -paint radius simulate an oil painting -perceptible set each pixel whose value is less than |epsilon| to -epsilon or epsilon (whichever is closer) otherwise the pixel value remains unchanged. -ping efficiently determine image attributes -pointsize value font point size -polaroid angle simulate a Polaroid picture -poly terms build a polynomial from the image sequence and the corresponding terms (coefficients and degree pairs). -posterize levels reduce the image to a limited number of color levels -precision value set the maximum number of significant digits to be printed -preview type image preview type -print string interpret string and print to console -process image-filter process the image with a custom image filter -profile filename add, delete, or apply an image profile -quality value JPEG/MIFF/PNG compression level -quantize colorspace reduce image colors in this colorspace -quiet suppress all 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 -red-primary point chromaticity red primary point -regard-warnings pay attention to warning messages. -region geometry apply options to a portion of the image -remap filename transform image colors to match this set of colors -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 -respect-parentheses settings remain in effect until parenthesis boundary. -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 seed a new sequence of pseudo-random numbers -segment values segment an image -selective-blur geometry selectively blur pixels within a contrast threshold -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 -sigmoidal-contrast geometry increase the contrast without saturating highlights or shadows -size geometry width and height of image -sketch geometry simulate a pencil sketch -smush offset smush an image sequence together -solarize threshold negate all pixels above the threshold level -splice geometry splice the background color into the image -spread radius displace image pixels by a random amount -statistic type geometry replace each pixel with corresponding statistic from the neighborhood -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 -swap indexes swap two images in the image sequence -swirl degrees swirl image pixels about the center -synchronize synchronize image to storage device -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 -tile-offset geometry set the image tile offset -tint value tint the image with the fill color -transform affine transform image -transparent color make this color transparent within the image -transparent-color color transparent color -transpose flip image in the vertical direction and rotate 90 degrees -transverse flop image in the horizontal direction and rotate 270 degrees -treedepth value color tree depth -trim trim image edges -type type image type -undercolor color annotation bounding box color -unique-colors discard all but one of any pixel 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 -vignette geometry soften the edges of the image in vignette style -virtual-pixel method access method for pixels outside the boundaries of the image -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 force all pixels above the threshold into white -write filename write images to this file