Resize images via drag and drop on OSX with good quality

Question

I want to be able to drag and drop images on an application(icon) which preferably doesn't run. This application has to resize the images to 600x450px and drop them somewhere.

I already created an Automator action which does exactly that but the quality is less then stellar compared to having it resized via the Preview-function or Photoshop. Below you can find an example pictures resized in Automator and Photoshop.

While there are Photoshop Automator Actions http://www.robotphotoshop.com/?page_id=8 they aren't compatible with Photoshop CS6 yet.

So for now I'm looking for something else which does the job with good quality and compression.

Automator resized picture

Photoshop resized picture

Answer 1

You could just create an Automator application but use ImageMagick instead. It can be installed with Homebrew (brew install imagemagick).

/usr/local/bin/mogrify -filter Lanczos2 -resize 500x -format jpg -quality 96 -path ~/Desktop/ "$@"

Lanczos2 (2-pole Lanczos) is very similar to Catrom or Photoshop's bicubic option. Compared to Lanczos (Lanczos3), the output images are slightly less sharp; ringing artifacts are less common but Moiré patterns are more common.

You can compare the different filters with a command like this: for f in Bartlett Blackman Bohman Box Catrom Gaussian Hanning Hermite Lagrange Lanczos Lanczos2 Mitchell Parzen Point Robidoux Sinc Spline Triangle Welsh; do convert -filter $f -resize 50% input.png $f.png; done.

You might also apply sharpening before or after resizing images, even though many resizing filters don't need it in my opinion. -sharpen 0x0.4+0.8 would correspond to applying an unsharp mask with a radius of 0.4 and 80% amount in Adobe CS applications. The first parameter (the radius of the convolution kernel) can usually be left as zero so it's set automatically.

I made a visual comparison of different resampling options for another answer: http://f.cl.ly/items/3W290e221m3w1b3x1A0H/downsampling%20test.png

Answer 2

Pixelmator supports Automator, but I do not know the quality of the results.

Answer 3

Have a look at TurboTool for just another way to create a Drag&Drop solution from a command line program with ImageMagick.

On the website you'll find a Quick Example to resize an image.

Hope it helps.