Takes a folder of images and combines them together in rows and columns for a one output image, using the ImageMagick CLI

image-magick-cli.sh

# Loops through all the .png images in the current folder and assigns their filename to an element of the array
counter=0
for i in `ls -1 ./*.png` ; do
    images[$counter]=$i;
    let counter=counter+1;
done

# Loops through the images array, based on the ROWS and COLS spec, to determine how many items rows and columns there will be when merging. Plenty of improvements here
ROWS=2
COLS=4
for (( c=0; c<$ROWS; c++ )) ; do
    # Specifies the start of the images array to be used per row
    imageIndexStart=$(expr $c \* $COLS)
    # Specifies the end of the images array to be used per row
    imageIndexEnd=$(expr $imageIndexStart + $COLS - 1)

    echo "ROW = $c; RANGE = $imageIndexStart - $imageIndexEnd"

    # Creates a string of the images to be composed into a row
    l=""
    for (( j=$imageIndexStart; j<=$imageIndexEnd; j++ )) ; do
        echo ${images[j]}
        l=$(echo $l ${images[j]})
    done

    # Using the string of images makes the row into it's own image
    convert $l +append row_$c.png
done

# Using each image created for a row merge these all together for the final image
convert $(ls row_*.png) -append output.png

# Delete the intermediate row images
rm row_*.png