rgb2bmp

#!/bin/sh

usage() {
  local p=$(basename $0)
  cat <<EOF >&2
$p - Convert between BMP and RGB565/RGB8888(RGB32)
Usage: $p input.bmp output.rgb32 [WxH]
Example:
  $ $p foo.bmp foo.rgb32
  $ $p foo.bmp foo.rgb565
  $ $p foo.rgb565 foo.bmp 1280x720
  $ $p foo.rgb32 foo.bmp 1280x720
NOTE:
- Suffix MUST be in either bmp/rgb32/rgb8888/rgb565.
EOF
  exit 0
}

rgb32_to_bmp() {
  local ifile=$1 ofile=$2 geom=$3

  # rgb8888 -> bmp
  ffmpeg \
  -f rawvideo -vcodec rawvideo -pix_fmt rgb32 -s $geom -i $ifile \
  -f image2 -vcodec bmp $ofile
}

rgb565_to_bmp() {
  local ifile=$1 ofile=$2 geom=$3

  # rgb565 -> bmp
  ffmpeg \
  -f rawvideo -vcodec rawvideo -pix_fmt rgb565 -s $geom -i $ifile \
  -f image2 -vcodec bmp $ofile
}

bmp_to_rgb32() {
  local ifile=$1 ofile=$2

  # bmp -> rgb8888
  ffmpeg \
  -vcodec bmp -i $ifile \
  -vcodec rawvideo -f rawvideo -pix_fmt rgb32 $ofile
}

bmp_to_rgb565() {
  local ifile=$1 ofile=$2

  # bmp -> rgb565
  ffmpeg \
  -vcodec bmp -i $ifile \
  -vcodec rawvideo -f rawvideo -pix_fmt rgb565 $ofile
}

run() {
  local ifile=$1 ofile=$2 geom=$3
  local itype=${ifile##*.}
  local otype=${ofile##*.}

  case "$itype" in
  bmp)
    case "$otype" in
    rgb32|rgb8888)  bmp_to_rgb32 $ifile $ofile;;
    rgb565)        bmp_to_rgb565 $ifile $ofile;;
    *) usage;;
    esac
    ;;
  rgb32|rgb8888)  rgb32_to_bmp $ifile $ofile $geom;;
  rgb565)        rgb565_to_bmp $ifile $ofile $geom;;
  *) usage;;
  esac
}

test $# -gt 0 || usage
run "$@"