▁is ▁drawn ▁on ▁the ▁screen , ▁how ▁to ▁display ▁it ▁in ▁various ▁screen ▁resolution s ▁and ▁if ▁the ▁image ▁is ▁com pressed . ▁ ▁The ▁content ▁of ▁this ▁chunk ▁is ▁as ▁follows : ▁ ▁B OD Y : ▁Image ▁data ▁ ▁The ▁B OD Y ▁chunk ▁is ▁usually ▁the ▁last ▁chunk ▁in ▁a ▁file , ▁and ▁the ▁largest . ▁ ▁In ▁IL B M ▁files ▁the ▁B OD Y ▁chunk ▁stores ▁the ▁actual ▁image ▁data ▁as ▁inter le aved ▁bit plan es ▁( and ▁optional ▁mask ) ▁by ▁row . ▁The ▁bit plan es ▁appear ▁first ▁from ▁ 1 ▁to ▁n , ▁followed ▁by ▁the ▁mask ▁plane . ▁If ▁the ▁image ▁is ▁un com pressed ▁then ▁each ▁line ▁will ▁be ▁made ▁up ▁of ▁( width ▁+ ▁ 1 5 ) ▁/ ▁ 1 6 ▁ 1 6 - bit ▁values ▁( i . e . ▁one ▁bit ▁per ▁pixel , ▁rounded ▁up ▁to ▁the ▁nearest ▁multiple ▁of ▁ 1 6 - bits .) ▁If ▁it ▁is ▁com pressed ▁then ▁each ▁line ▁is ▁com pressed ▁individually ▁and ▁is ▁always ▁a ▁multiple ▁of ▁ 1 6 - bits ▁long ▁when ▁com pressed . ▁ ▁In ▁P B M ▁files , ▁the ▁B OD Y ▁chunk ▁is ▁simpler ▁as ▁un com pressed ▁it ▁is ▁just ▁a ▁continuous ▁stream ▁of ▁bytes ▁containing ▁image ▁data . ▁ ▁Com pression ▁ ▁If ▁an ▁image ▁is ▁com pressed , ▁each ▁row ▁of ▁data ▁( but ▁not ▁each ▁bit plane ) ▁is ▁com pressed ▁individually , ▁including ▁the ▁mask ▁data ▁if