For the Ponyo post I had a bunch of PNG 853×480 screenshots. At first, the post used 300×168 images, resized by the blog’s engine, such as the below one:
However, the ideal width for images in this blog is about 600 pixels:
For resizing multiple files I recurred to ImageMagick command line tools (here are some Windows Binary Releases). On Windows command prompt, it’s enough to type:
forfiles /M *.png /C “cmd /c convert -resize 70% @file resized_@file”
That way all of the images will have resized versions, at 70% their original size, yielding a 597-pixels width.