test-discolour-layer-v1.py

#!/usr/bin/env python
#
# -------------------------------------------------------------------------------------
#
# Copyright (c) 2013, Jose F. Maldonado
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without modification, 
# are permitted provided that the following conditions are met:
#
#    - Redistributions of source code must retain the above copyright notice, this 
#    list of conditions and the following disclaimer.
#    - Redistributions in binary form must reproduce the above copyright notice, 
#    this list of conditions and the following disclaimer in the documentation and/or 
#    other materials provided with the distribution.
#    - Neither the name of the author nor the names of its contributors may be used 
#    to endorse or promote products derived from this software without specific prior 
#    written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY 
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT 
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
# TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR 
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 
# DAMAGE.
#
# -------------------------------------------------------------------------------------
#
# This file is a basic example of a Python plug-in for GIMP.
#
# It can be executed by selecting the menu option: 'Filters/Test/Discolour layer v1'
# or by writing the following lines in the Python console (that can be opened with the
# menu option 'Filters/Python-Fu/Console'):
# >>> image = gimp.image_list()[0]
# >>> layer = image.layers[0]
# >>> gimp.pdb.python_fu_test_discolour_layer_v1(image, layer)

from gimpfu import *

def discolour_layer_v1(img, layer) :
    ''' Converts a layer to gray scale, without modifying his type (RGB or RGBA).
    Note that this implementation is very inefficient, since it do not make use 
    of tiles or pixel regions. Also, it has a bug which prevents to undo the 
    changes made by this function.
    
    Parameters:
    img : image The current image.
    layer : layer The layer of the image that is selected.
    '''
    # Indicates that the process has started.
    gimp.progress_init("Discolouring " + layer.name + "...")

    # Set up an undo group, so the operation will be undone in one step.
    pdb.gimp_image_undo_group_start(img)

    # Iterate over all the pixels and convert them to gray.
    try:
        for x in range(layer.width):
            # Update the progress bar.
            gimp.progress_update(float(x) / float(layer.width))

            for y in range(layer.height):
                # Get the pixel and verify that is an RGB value.
                pixel = layer.get_pixel(x,y)
            
                if(len(pixel) >= 3):
                    # Calculate his gray tone.
                    sum = pixel[0] + pixel[1] + pixel[2]
                    gray = int(sum/3)
                
                    # Create a new tuple representing the new color.
                    newColor = (gray,gray,gray) + pixel[3:]
                    layer.set_pixel(x,y, newColor)
        
        # Update the layer.
        layer.update(0, 0, layer.width, layer.height)

    except Exception as err:
        gimp.message("Unexpected error: " + str(err))
    
    # Close the undo group.
    pdb.gimp_image_undo_group_end(img)
    
    # End progress.
    pdb.gimp_progress_end()

register(
    "python_fu_test_discolour_layer_v1",
    "Discolour layer v1",
    "Converts a layer to gray scale. Note that this implementation is very inefficient, since it do not make use of tiles. It also has a bug which damages the undo funcionality",
    "JFM",
    "Open source (BSD 3-clause license)",
    "2013",
    "<Image>/Filters/Test/Discolour layer v1",
    "RGB, RGB*",
    [],
    [],
    discolour_layer_v1)

main()