convert  test.png -channel green  -negate  negate_green.png
convert  negate_green.png  -channel green  -negate  negate_restore.png
  convert  test.png  +level-colors green,gold   levelc_grn-gold.png
convert test.png  +level-colors ,DodgerBlue   levelc_dodger.png
  convert test.png  +level-colors ,Gold         levelc_gold.png
  convert test.png  +level-colors ,Lime         levelc_lime.png
  convert test.png  +level-colors ,Red          levelc_red.png

  convert test.png  +level-colors Navy,         levelc_navy.png
  convert test.png  +level-colors DarkGreen,    levelc_darkgreen.png
  convert test.png  +level-colors Firebrick,    levelc_firebrick.png

  convert test.png  -size 1x1 xc:Yellow \
            -fx 'u*v.p{0,0}'    fx_linear_white.png


convert test.png  -size 1x2  gradient:gold-firebrick \
            -fx 'v.p{0,0}*u+v.p{0,1}*(1-u)'   fx_linear_color.png

convert test.png -size 1x2  gradient:gold-firebrick \
            -fx 'v.p{0,1}+(v.p{0,0}-v.p{0,1})*u^4'  fx_non-linear.png


convert  test.png  -fill red  -tint 40 tint_red.png

    convert test.png \( +clone -matte  -channel A \
              -fx 'tint=intensity-.5; (1-4*tint*tint)*a* 1.0' +channel \
              -fill gold -colorize 100% \) -composite  tint_diy.png


    convert test.png \( +clone +matte -fill gold -colorize 100% \) \
              -compose overlay -composite  tint_overlay.png

    convert test.png \
            \( -size 150x100 tile:tile_disks.jpg \
               +clone +swap -compose overlay -composite \) \
            -compose SrcIn -composite  tint_overlay_pattern.png
  convert  rose:  -modulate 100,100,100  mod_noop.gif
 convert rose:   -modulate 100,100,0      mod_hue_0.gif
  convert rose:   -modulate 100,100,33.3   mod_hue_33.gif
  convert rose:   -modulate 100,100,66.6   mod_hue_66.gif
  convert rose:   -modulate 100,100,100    mod_hue_100.gif
  convert rose:   -modulate 100,100,133.3  mod_hue_133.gif
  convert rose:   -modulate 100,100,166.6  mod_hue_166.gif
  convert rose:   -modulate 100,100,200    mod_hue_200.gif