ImageMagick

utilities

displayslideshows of Images
convertconvert and Modify Images
importread images from the on screen display
identifyprint the details of images, that IM sees
mogrifyin-place batch processing
compositeoverlaying images in special ways
montagegenerating arrays of thumbnails

 

remarks

one of the most important points to remember with IM, and one that confuses both new users and experienced users, is that...

ImageMagick works with Ordered Lists of Images, not single images

that is IM deals not with just one image, but potentially a ordered list of images, be they separate individual images, a set of images that layer on top of each other, or the frames of an animation

 

examples

  $> import -screen filename.png

  $> convert marjana1.jpg -resize 640x360 pic11.jpg

by default the aspect ratio of the image is preserved. only to shrink larger images use '>' flag. only enlarge smaller images use '<' flag. to fill area flag is '^' if you dont want to preserved aspect ratio then use '!' flag

  $> convert -resize 720 *.png

which will resize all the png’s in that directory, uniformly, to a width of 720px. they however will bare the same name as the originals

  $> identify output.png

  $>  convert test.png -transparent white transparent.png
that changed all the white in the test.png to transparent

    $>  convert pixel.png points.txt
    $>  cat points.txt | grep black | 
              sed 's/^([0-9]+),([0-9]+).*$/\1 \2/' | 
              sort -n > points_coord.dat
if pixel.png is just white/black pixels then points.txt will contain coordinates with atributes black/white. so you create file pixel.png with size 100x100 pixels, do several 1x1 points with brash (color - black), save this file, convert it - and you have text file which you can grep with 'black' and clear garbage with sed and after that sorted it. done! you have list of coordinates of all your dots in initial file! hack!