Making an image grayscale (monochrome)

Source image:

if not exist toes.png xcopy /y %PICTLIB%20130713\toes.png
set SRC_TOES=toes.png

The left box contains code that generates one or more images and the mean, standard deviation, colorspace and gamma of each.

The images are not shown here but are used for regression testing.

The middle box contains code that generates a single image.

The right box show the image generated by the code in the middle box.

for %%T in (monochrome) do (
for %%H in (--) do (
%IMG7%magick ^
  %SRC% ^
  -monochrome ^
  %MM_INFO% ^
  mm_%%T.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -monochrome ^
  mmt_monochrome.png

for %%T in (modulate) do (
for %%H in (HCL,HCLp,HSL,HSI,HSB,HSV) do (
%IMG7%magick ^
  %SRC% ^
  -set option:modulate:colorspace %%H ^
  -modulate 100,0,100 ^
  %MM_INFO% ^
  mm_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -modulate 100,0,100 ^
  mmt_modulate.png

for %%T in (grayscale) do (
FOR %%H ^
IN (Rec601Luminance,Rec709Luminance,Rec601Luma,Rec709Luma,Lightness,Average,MS,RMS,Brightness) ^
DO (
%IMG7%magick ^
  %SRC% ^
  -grayscale %%H ^
  %MM_INFO% ^
  mm_gr_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -grayscale RMS ^
  mmt_gr_RMS.png

for %%T in (colorspace_channel_1) do (
FOR %%H ^
IN (YCC,YDbDr,YCbCr,YIQ,YPbPr,YUV,LCH,LCHab,LCHuv,Lab) ^
DO (
%IMG7%magick ^
  %SRC% ^
  -colorspace %%H ^
  -channel GB -evaluate set 50%% ^
  -colorspace sRGB ^
  %MM_INFO% ^
  mm_cc1_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -colorspace Lab ^
  -channel GB -evaluate set 50%% ^
  -colorspace sRGB ^
  mmt_cc1_Lab.png

for %%T in (colorspace) do (
FOR %%H ^
IN (Gray,LinearGray) ^
DO (
%IMG7%magick ^
  %SRC% ^
  -colorspace %%H ^
  %MM_INFO% ^
  mm_cs_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -colorspace Gray ^
  mmt_cs_gray.png

%IMG7%magick -list intensity

for %%T in (colorspace_gray) do (
FOR /F %%H ^
IN (mmIntensity.lis) ^
DO (
%IMG7%magick ^
  %SRC% ^
  -intensity %%H ^
  -colorspace gray ^
  +intensity ^
  %MM_INFO% ^
  mm_cgr_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -intensity Lightness ^
  -colorspace gray ^
  +intensity ^
  mmt_cgr_Lightness.png

for %%T in (single_channel) do (
FOR %%H IN (Red) DO (
%IMG7%magick ^
  %SRC% ^
  -separate -delete 1-2 ^
  %MM_INFO% ^
  mm_1c_%%H.png>>mmList.csv
)

FOR %%H IN (Green) DO (
%IMG7%magick ^
  %SRC% ^
  -separate -delete 0,2 ^
  %MM_INFO% ^
  mm_1c_%%H.png>>mmList.csv
)

FOR %%H IN (Blue) DO (
%IMG7%magick ^
  %SRC% ^
  -separate -delete 0-1 ^
  %MM_INFO% ^
  mm_1c_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -separate -delete 0,2 ^
  mmt_1c_Green.png

for %%T in (poly) do (
FOR %%H IN (StrongRed) DO (
%IMG7%magick ^
  %SRC% ^
  -separate ^
  -poly "3,1 -1,1 -1,1" ^
  %MM_INFO% ^
  mm_poly.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  -separate ^
  -poly "3,1 -1,1 -1,1" ^
  mmt_poly.png

for %%T in (polyFloat) do (
FOR %%H IN (StrongRed) DO (
rem %IMG7%magick ^
rem   %SRC% ^
rem   -separate ^
rem   -poly "3,1 -1,1 -1,1" ^
rem   -auto-level ^
rem   %MM_INFO% ^
rem   mm_polyf.png>>mmList.csv
)
)

rem %IMG7%magick ^
rem   %SRC_TOES% ^
rem   -separate ^
rem   -poly "3,1 -1,1 -1,1" ^
rem   -auto-level ^
rem   mmt_polyf.png

set SPEC_COL=khaki

for %%T in (colour_distance) do (
FOR %%H IN (%SPEC_COL%) DO (
%IMG7%magick ^
  %SRC% ^
  ^( +clone -fill %%H -colorize 100 ^) ^
  -compose Difference -composite ^
  -grayscale RMS ^
  %MM_INFO% ^
  mm_cd_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  ^( +clone -fill khaki -colorize 100 ^) ^
  -compose Difference -composite ^
  -grayscale RMS ^
  mmt_cd_khaki.png

for %%T in (colour_distance_2) do (
FOR %%H IN (%SPEC_COL%) DO (
%IMG7%magick ^
  %SRC% ^
  ^( +clone -fill %%H -colorize 100 -negate ^) ^
  -compose Difference -composite ^
  -grayscale RMS ^
  -negate ^
  %MM_INFO% ^
  mm_cd2_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  ^( +clone -fill khaki -colorize 100 -negate ^) ^
  -compose Difference -composite ^
  -grayscale RMS ^
  -negate ^
  mmt_cd2_khaki.png

for %%T in (colour_distance_Lab) do (
FOR %%H IN (%SPEC_COL%) DO (
%IMG7%magick ^
  %SRC% ^
  ^( +clone -fill %%H -colorize 100 ^) ^
  -colorspace Lab ^
  -compose Difference -composite ^
  -grayscale RMS ^
  -set colorspace sRGB ^
  %MM_INFO% ^
  mm_cdLab_%%H.png>>mmList.csv
)
)

%IMG7%magick ^
  %SRC_TOES% ^
  ^( +clone -fill khaki -colorize 100 ^) ^
  -colorspace Lab ^
  -compose Difference -composite ^
  -grayscale RMS ^
  -set colorspace sRGB ^
  mmt_cdLab_khaki.png

Grayscale:

FOR %%H ^
IN (Rec601Luminance,Rec709Luminance,Rec601Luma,Rec709Luma,^
Lightness,Average,MS,RMS,Brightness) ^
DO (
  set twiddle=0
  if %%H==Rec601Luminance set twiddle=1
  if %%H==Rec709Luminance set twiddle=1

  if !twiddle!==1 (
    set tweakRgb=-set colorspace RGB -colorspace sRGB
  ) else (
    set tweakRgb=
  )

%IMG7%magick ^
  %SRC_TOES% ^
  -grayscale %%H ^
  -gravity SouthWest -undercolor #fff -annotate 0 "grayscale %%H" ^
  !tweakRgb! ^
  toes_gr_%%H.png
)

Colorspace gray:

FOR %%H ^
IN (Rec709Luminance,Rec709Luma,Brightness) ^
DO (
%IMG7%magick ^
  %SRC_TOES% ^
  -intensity %%H ^
  -colorspace gray ^
  +intensity ^
  -gravity SouthWest -undercolor #fff -annotate 0 "intensity %%H" ^
  toes_cgr_%%H.png
)

Colorspace channel:

FOR %%H ^
IN (YCC,YIQ,LCH,Lab) ^
DO (
%IMG7%magick ^
  %SRC_TOES% ^
  -colorspace %%H ^
  -channel GB -evaluate set 50%% ^
  -colorspace sRGB ^
  -gravity SouthWest -undercolor #fff -annotate 0 "colorspace %%H" ^
  toes_cc1_%%H.png
)

Single channel 1:

%IMG7%magick ^
  %SRC_TOES% ^
  -separate -delete 1-2 ^
  -gravity SouthWest -undercolor #fff -annotate 0 Red ^
  toes_1c_red.png

%IMG7%magick ^
  %SRC_TOES% ^
  -separate -delete 0,2 ^
  -gravity SouthWest -undercolor #fff -annotate 0 Green ^
  toes_1c_green.png

%IMG7%magick ^
  %SRC_TOES% ^
  -separate -delete 0-1 ^
  -gravity SouthWest -undercolor #fff -annotate 0 Blue ^
  toes_1c_blue.png

Colour distance:

call %PICTBAT%hashCol %SRC_TOES% -crop 10x10+116+86

%IMG7%magick ^
  %SRC_TOES% ^
  ^( +clone -fill %HASH_COL% -colorize 100 ^) ^
  -compose Difference -composite ^
  -grayscale RMS ^
  toes_cd.png

Colour distance 2:

%IMG7%magick ^
  %SRC_TOES% ^
  ^( +clone -fill %HASH_COL% -colorize 100 -negate ^) ^
  -compose Difference -composite ^
  -grayscale RMS ^
  -negate ^
  toes_cd2.png

Colour distance using smallest distance to two sampled areas:

set ONE_HASH_COL=%HASH_COL%

call %PICTBAT%hashCol %SRC_TOES% -crop 10x10+225+116

%IMG7%magick ^
  %SRC_TOES% ^
  ^( -clone 0 ^
    ^( +clone -fill %ONE_HASH_COL% -colorize 100 ^) ^
    -compose Difference -composite ^
    -grayscale RMS ^
  ^) ^
  ^( -clone 0 ^
    ^( +clone -fill %HASH_COL% -colorize 100 ^) ^
    -compose Difference -composite ^
    -grayscale RMS ^
  ^) ^
  -delete 0 ^
  -compose Darken -composite ^
  toes_cd3.png

Colour distance Lab:

%IMG7%magick ^
  %SRC_TOES% ^
  ^( +clone -fill %HASH_COL% -colorize 100 ^) ^
  -colorspace Lab ^
  -compose Difference -composite ^
  -grayscale RMS ^
  -set colorspace sRGB ^
  toes_cd4.png

Col filt. Create a hald-clut, creating a mask that is lightest at the hue (channel a and b of Lab) of the toes ...

%IMG7%magick ^
  hald:8 ^
  ( +clone -fill %HASH_COL% -colorize 100 ) ^
  -colorspace Lab ^
  -compose Difference -composite ^
  -gamma 0.5 ^
  -separate ^
  -delete 0 ^
  -compose Add -composite ^
  -gamma 2 ^
  -set colorspace sRGB ^
  -negate ^
  toes_cfDist.png

... and apply it:

%IMG7%magick ^
  %SRC_TOES% ^
  ( -clone 0 -modulate 100,0,100 ) ^
  +swap ^
  ( -clone 1 ^
    toes_cfDist.png -hald-clut ^
    -auto-level ^
    -write toes_cf_halded.png ^
  ) ^
  -composite ^
  toes_cf.png

The grayscale image is roughly what a B&W camera would show with a skin-colour filter over the lens.

The colour image has the toes at unchanged saturation, and the grass at lower saturation.