#!/usr/bin/env python

# Luminosity Masks
# by Mike Rosulek
#
# Implements (and extends) Tony Kuyper's luminosity mask techniques in GIMP.
#
# Changelog:
#   v1.0 [2011-08-01]: Initial release
#   v1.1 [2011-08-02]: Choose desaturation mode

from gimpfu import *

norm = {
    'lights': (lambda x: x/255.0),
    'darks':  (lambda x: (255 - x)/255.0),
    'mids':   (lambda x: (255 - 2*abs(127.5-x))/255.0)
}

def ncurve(x):
    return( int(255*x) )

desaturate_mode = {
    'light': DESATURATE_LIGHTNESS,
    'lum':   DESATURATE_LUMINOSITY,
    'avg':   DESATURATE_AVERAGE
}

def lum_mask(timg, tdrawable, baselayer, mode, region, expand):
    if not pdb.gimp_drawable_is_layer(tdrawable):
        pdb.gimp_message("Can only be called on a layer, not on a mask")
        return()
    
    timg.undo_group_start()

    if pdb.gimp_layer_get_mask(tdrawable) != None:
        pdb.gimp_layer_remove_mask(tdrawable, MASK_DISCARD)

    duplicated = 0

    if not pdb.gimp_drawable_is_gray(baselayer):
        newbase = pdb.gimp_layer_new_from_drawable(baselayer, timg)
        pdb.gimp_drawable_set_name(newbase, "Desaturated Luminosity Mask")
        pdb.gimp_image_add_layer(timg, newbase, -1)
        pdb.gimp_desaturate_full(newbase, desaturate_mode[mode])
        duplicated = 1
        baselayer = newbase

    mask = pdb.gimp_layer_create_mask(baselayer, ADD_COPY_MASK)
    pdb.gimp_layer_add_mask(tdrawable, mask)

    if duplicated:
        pdb.gimp_image_remove_layer(timg, baselayer)

    mynorm = norm[region]
    pdb.gimp_curves_explicit(mask, 0,256,
        [ ncurve(mynorm(x)**(2**(-expand))) for x in range(256) ] )

    pdb.gimp_layer_set_edit_mask(tdrawable, FALSE)


    timg.undo_group_end()
    gimp.displays_flush

register(
        "luminosity_mask",
        "Add luminosity mask to this layer",
        "Add luminosity mask to this layer",
        "Mike Rosulek",
        "Mike Rosulek",
        "v1.0, August 2011",
        "<Image>/Filters/Generic/Luminosity Mask...",
#        "<Image>/Layer/Mask/Add Luminosity Mask...",
        "RGB*, GRAY*",
        [
                (PF_LAYER, "layer", "Use luminosity from:", None),
                (PF_RADIO, "mode", "Desaturation Mode", "lum", (("Lightness","light"), ("Luminosity","lum"), ("Average","avg"))),
                (PF_RADIO, "tone", "Tone Region", "lights", (("Lights","lights"), ("Darks","darks"), ("Midtones","mids"))),
                (PF_SLIDER, "expand", "Expand/contract", 0, [-3,3,0.1])
        ],
        [],
        lum_mask)

main()