#!/bin/bash
# magick input.png -colorspace Gray -auto-level -dither FloydSteinberg -depth 8 output.png

INPUT="$1"
OUTPUT_DIR="tiles"

#Create OUTPUT_DIR if it doesn't exist
mkdir -p "$OUTPUT_DIR"

#Get image dimensions
WIDTH=$(identify -format "%w" "$INPUT")
HEIGHT=$(identify -format "%h" "$INPUT")
echo "Image dimensions: $WIDTH x $HEIGHT"

#Tile dimensions
TILE_WIDTH=8192
TILE_HEIGHT=8192

echo "Cutting image into tiles of ${TILE_WIDTH}x${TILE_HEIGHT}..."

# Loop over vertical and horizontal positions
count=0
for (( y=0; y<HEIGHT; y+=TILE_HEIGHT )); do
    for (( x=0; x<WIDTH; x+=TILE_WIDTH )); do

        W=$(($TILE_WIDTH < $((WIDTH - x)) ? $TILE_WIDTH : $((WIDTH - x))))
        H=$(($TILE_HEIGHT < $((HEIGHT - y)) ? $TILE_HEIGHT : $((HEIGHT - y))))

        # Filename encodes position: tile_x<x>_y<y>_w<W>_h<H>.png
        TILE_FILE="$OUTPUT_DIR/tile_x${x}_y${y}_w${W}_h${H}.png"
        echo "Creating $TILE_FILE"
        # convert "$INPUT" -crop "${TILE_WIDTH}x${TILE_HEIGHT}+${x}+${y}" +repage "$TILE_FILE"
        vips extract_area "$INPUT" "$TILE_FILE" "$x" "$y" "$W" "$H"
        ((count++))
    done
done

echo "Done. $count tiles created."