HOW TO - FIND THE REGIONS OF LEAST/MOST DIFFERENCE

INGREDIENTS

One original layer

FORMULA

Duplicate the original layer
Use 'selective gaussian blur' on the new layer
Set the layer to difference mode
Copy visible
Paste onto the new layer and anchor.
Threshold to (GUESS 16)..255
Invert (the new layer now contains a mask of all the pixels that are NOT different from neighbours)
~~~~
- Smooth the difference mask finally (via select->smooth)

USAGE

To perform an automated touchup while leaving areas of high-frequency detail intact.
1. Place the filtered image on a layer above the original
2. Add a layer mask
3. Copy+paste the difference mask into the layer mask. Remember white areas are solid, black are transparent.

TRIAL:

DiffMask	Difference mask.
DiffMaskSmooth	Vectorsmoothed difference mask.
AutoAAed	Automatically AAed using my vectorscaler. This is the filtered version that will be masked.
Combined	AutoAAed masked by DiffMask.
CombSmooth	AutoAAed masked by DiffMaskSmooth.
CombIndx	Combined indexized to the original palette
CombSmoothIndx	CombSmooth indexized to the original palette

PRESETS:

Situation	Selective Gaussian Blur options
Photo	RADIUS 5, THRESHOLD 70
Pixelart	RADIUS 3, THRESHOLD 50 (used for DiffMask)

PLUGIN: selectdiffs.py

CODE


import newvector as nv

def perLayer(image, layer, blur_radius = 3, blur_delta = 50, threshold = 16, invert = False, smooth=False):
    "'Smart' Auto-antialiasing. Leaves highresolution detail alone."
    newlayer = pdb.gimp_layer_copy (layer,False)
    # need to add it to image here?

    pdb.plug_in_sel_gauss (image, newlayer, blur_radius, blur_delta)
    newlayer.mode = DIFFERENCE_MODE

    #need to flush displays here?

    buf = pdb.gimp_edit_named_copy_visible (image,'temp')
    fsel = pdb.gimp_edit_named_paste (newlayer,buf,False)
    pdb.gimp_floating_sel_anchor(fsel)

    pdb.gimp_threshold(newlayer, threshold, 255)
    if invert:
        pdb.gimp_invert(newlayer)

    if smooth:
        # do something I haven't decided yet with pdb.plug_in_smooth_selection(image, newlayer) here
        pass

    #Add a layer mask and chuck the layer content across
    mask = pdb.gimp_layer_create_mask (newlayer, ADD_COPY_MASK)
    pdb.gimp_layer_add_mask(newlayer,mask)
    return newlayer

FURTHERING

Clarifying the picture further through manual mask editing is quickly rewarding
Another approach (needed for processing animations) is to identify isolated pixels (the white of her eye is a pixel with no like pixels surrounding it, for instance)

RELATIVES