#
# how to emulate Irfanview's Color balance correction
#

### prepare source image ################################################

SRC="test.ppm"
#ppmmake rgb:80/80/80  200 100 > $SRC		# plain
 ppmwheel 256                  > $SRC		# color wheel

### method1: by pnmarith ################################################

W=`pnmfile $SRC | awk '{print $4}'`		# get width
H=`pnmfile $SRC | awk '{print $6}'`		# get height
ppmmake rgb:00/28/00  $W $H > to_add		#    G+=40
ppmmake rgb:14/00/3c  $W $H > to_sub		# R-=20, B-=60
pnmarith -add  $SRC to_add > temp		# do add
pnmarith -sub  temp to_sub > result1.ppm	# do sub
rm  to_add to_sub temp				# clean up

### method2: by pamfunc #################################################

cat $SRC | ppmtorgb3				# divide to 3 pgm
pamfunc -sub  20  noname.red > temp.red		# R-=20
pamfunc -add  40  noname.grn > temp.grn		# G+=40
pamfunc -add -60  noname.blu > temp.blu		# B-=60
rgb3toppm  temp.red temp.grn temp.blu > result2.ppm	# bind back to ppm
rm  noname.red noname.grn noname.blu		# clean up
rm    temp.red   temp.grn   temp.blu		# clean up

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