If you're looking for an efficient way to resize images, especially in a batch mode, the command line approach may be the answer.
OS X
OS X comes with a tool called sips, which stands for Scriptable Image
Processing System. sips modifies images in-place, i.e. files passed in as
arguments are altered; adding --out [filename] makes sips operate on a copy.
The two common parameters for sips are -z and -Z.
-z [height] [width]- it resizes the image according to specified dimensions, which may alter the aspect ratio of the image.-Z [heightwidth]- it defines the maximum dimensions for both height and width, which keeps the aspect ratio of the image.
λ sips -z 768 1024 example.pngλ sips -Z 1024 example.pngλ sips -z 768 1024 *.pngIt is also very easy to convert files from one format ot another, using -s
parameter.
λ sips -s format jpeg test.png --out test.jpgLinux
On Linux we can use mogrify from the ImageMagick toolbox to get the same
functionality as with sips.
The most basic command would be resizing an image to specified dimensions, keeping the aspect ratio.
mogrify -resize 1024x768 example.pngIf we need to resize to exact size, a ! sign must be added to the specified
dimensions.
mogrify -resize 1024x768! example.pngBatch processing is also possible.
mogrify -resize 50% *.jpgAs well as converting from one format to another.
mogrify -format jpg *.pngSummary
Resizing and converting formats are probably the most common tasks when it comes
to image manipulation. Both sips and mogrify provide more ways to transform
images than covered in this short post. Feel free to check their docs to learn
more.