Adobe Photoshop script to resize images to fit inside a 1024px box.

PsResizeLongestSide1024.jsx

/***************************
 NOT MAINTAINED! from ~2015
****************************/

// photoshop script to resize images proportionally to fit inside a 1024px box i.e. longest side/edge will equal 1024px
// useful when scaling down many large photos for web use, simply toss in a batch action

var activeDoc = app.activeDocument
var docWidth = activeDoc.width
var docHeight = activeDoc.height

activeDoc.changeMode(ChangeMode.RGB)
activeDoc.flatten()

// only resize images with an edge greater than 1024px
if (docHeight.as('px') > 1024 || docWidth.as('px') > 1024) {
  if (docHeight > docWidth) {
    // portrait
    activeDoc.resizeImage(
      null, // width
      UnitValue(1024, 'px'), // height
      null, // resolution
      ResampleMethod.BICUBIC
    )
  } else {
    // landscape
    activeDoc.resizeImage(
      UnitValue(1024, 'px'), // width
      null, // height
      null, // resolution
      ResampleMethod.BICUBIC
    )
  }
}