A shell script to generates screenshot images from PSD files to submit to iTunes Connect (App Store). It removes the alpha channel of the source 5.5 inch images, and resizes and crops them to generate 4.7, 4 and 3.5 inch images.

genscreenshots.sh

#!/bin/sh
 
# settings ==========
filePrefix=""

destDir="./output/"
destDir5_5=$destDir"5.5inch/"
destDir4_7=$destDir"4.7inch/"
destDir4=$destDir"4inch/"
destDir3_5=$destDir"3.5inch/"
# ====================
 
# create dest directory
mkdir $destDir
mkdir $destDir5_5
mkdir $destDir4_7
mkdir $destDir4
mkdir $destDir3_5

# loop for 5.5inch
echo "5.5inch"
for i in 1 2 3 4 5
do
  destFilePath=$destDir5_5$filePrefix$i".png"
  echo $destFilePath
  convert $filePrefix$i".psd[0]" $destFilePath
  convert $destFilePath -background white -flatten $destFilePath
done

# loop for 4.7inch
echo "4.7inch"
for i in 1 2 3 4 5
do
  sourceFilePath=$destDir5_5$filePrefix$i".png"
  destFilePath=$destDir4_7$filePrefix$i".png"
  echo $destFilePath
  convert -resize x1334 $sourceFilePath $destFilePath
done
 
# loop for 4inch
echo "4inch"
for i in 1 2 3 4 5
do
  sourceFilePath=$destDir5_5$filePrefix$i".png"
  destFilePath=$destDir4$filePrefix$i".png"
  echo $destFilePath
  convert -resize 640x $sourceFilePath $destFilePath
  convert -crop 640x1136+0+0 $destFilePath $destFilePath
done

# loop for 3.5inch
echo "3.5inch"
for i in 1 2 3 4 5
do
  sourceFilePath=$destDir4$filePrefix$i".png"
  destFilePath=$destDir3_5$filePrefix$i".png"
  echo $destFilePath
  convert -crop 640x960+0+0 $sourceFilePath $destFilePath
done

Based on this gist:
https://gist.github.com/haranicle/55debc2e46ef643341cc

To use the shell script:

1. Install ImageMagick
2. Prepare 1.psd, 2.psd, 3.psd, 4.psd and 5.psd in 1242 x 2208 pixels for 5.5 inch screen iPhone. The filenames can have a prefix defined as filePrefix in the script.
3. Run the script where the PSD files are located.