Warn about top-left TGA field order when packing

[Aciz]

Not sure how trivially this could be implemented, but detecting top-left field order in itself on TGA files is very trivial. Top-left ordered TGA files draw upside-down on 2.60b clients, but correctly on ETe/ETL clients, so this is something that a mapper can easily overlook.

By checking the 17th byte of the TGA header for value 0x20, you can detect the field order of TGA files - if it's 0x20, the field order is top-left.

Sample bash script

#!/bin/sh

if [ $# -ne 1 ]; then
    echo "Usage: $0 <TGA file>"
    exit 1
fi

tga_file="$1"

if [ ! -f "$tga_file" ]; then
    echo "File not found: $tga_file"
    exit 1
fi

byte=$(xxd -s 17 -l 1 -p "$tga_file")
byte_decimal=$((16#$byte))

if (( byte_decimal & 0x20 )); then
    echo "The TGA file has a field order of top-left."
else
    echo "The TGA file has a field order of bottom-left."
fi