pixel_skew.py

#!/usr/bin/env python2

#   Gimp-Python - allows the writing of Gimp plugins in Python.
#   Copyright (C) 2024  draco18s <draco18s(at)gmail.com>
#
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation; either version 3 of the License, or
#   (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#   This code is slow as balls, its your own fault if you use this.
#
#   You should have received a copy of the GNU General Public License
#   along with this program.  If not, see <https://www.gnu.org/licenses/>.

from gimpfu import *
import time

gettext.install("gimp20-python", gimp.locale_directory, unicode=True)

def gimp_log(text):
    pdb.gimp_message(text)
    
def pixel_skew(img, layer, skew_angle):
    layer = skew_x(img, layer, skew_angle)
    layer = skew_y(img, layer, skew_angle)
    layer = skew_x(img, layer, skew_angle)

def skew_x(img, layer, skew_angle):
    skew_angle = skew_angle / 180 * 3.1415
    # Get the image's width and height
    width = layer.width
    height = layer.height
    
    A=-math.tan(skew_angle/2)
    # B=math.sin(skew_angle)
    
    centerX = (width/2)+0.5
    centerY = (height/2)+0.5
    
    readRegion=layer.get_pixel_rgn(0, 0, layer.width, layer.height)
    pixRead=readRegion[:,:]
    
    xoffset = centerY * A
    if xoffset < 0:
        xoffset = -xoffset
    
    nWidth = int(width + xoffset * 2)
    
    # pdb.gimp_message('New width: %s' % (nWidth))
    
    nHeight = height
    # layer_one = img.layer(img, "Skew", nWidth, nWidth, RGB_IMAGE, 100, NORMAL_MODE)
    layer_one = gimp.Layer(img, "Skew Layer", nWidth, nHeight)
    img.add_layer(layer_one,0)
    
    writeRegion=layer_one.get_pixel_rgn(0, 0, nWidth, nHeight)
    pixWrite=writeRegion[:,:]

    # Apply the transformation to each pixel in the layer
    for y in range(layer.height):
        for x in range(layer.width):
            # pdb.gimp_message('Getting pixel at index x,y: (%s,%s)' % (x,y))
            pixel = readRegion[x,y]
            v = (y-centerY) * A
            #if v < 0:
            #v = v + 0.01
            # pdb.gimp_message('Setting pixel at index x,y: (%s,%s)' % ((x + int(v + xoffset)) % nWidth,y))
            writeRegion[(x + int(v + xoffset)) % nWidth,y] = pixel
    return layer_one
    
def skew_y(img, layer, skew_angle):
    skew_angle = skew_angle / 180 * 3.1415
    # Get the image's width and height
    width = layer.width
    height = layer.height
    
    # A=-math.tan(skew_angle/2)
    B=math.sin(skew_angle)
    
    centerX = (width/2)+0.5
    centerY = (height/2)+0.5
    
    readRegion=layer.get_pixel_rgn(0, 0, layer.width, layer.height)
    pixRead=readRegion[:,:]
    
    yoffset = centerY * B
    if yoffset < 0:
        yoffset = -yoffset
    
    nWidth = width
    nHeight = int(height + yoffset*2)
    
    layer_one = gimp.Layer(img, "Skew Layer", nWidth, nHeight)
    img.add_layer(layer_one,0)
    
    writeRegion=layer_one.get_pixel_rgn(0, 0, nWidth, nHeight)
    pixWrite=writeRegion[:,:]

    # Apply the transformation to each pixel in the layer
    for y in range(layer.height):
        for x in range(layer.width):
            pixel = readRegion[x,y]
            v = (x-centerY) * B
            #if v < 0:
            #v = v + 0.01
            writeRegion[x, (y + int(v + yoffset)) % nHeight] = pixel
    return layer_one

register(
    "python-fu-pixel_skew",
    N_("Performs a pixel perfect skew"),
    "Performs a pixel perfect skew",
    "Draco18s",
    "Draco18s",
    "2024",
    N_("_Pixel Skew"),
    "RGB*, GRAY*",
    [
        (PF_IMAGE, "image",       "Input image", None),
        (PF_DRAWABLE, "drawable", "Input drawable", None),
        (PF_ADJUSTMENT, "skew",    _("Skew angle"),    0, (-180, 180, 1)),
    ],
    [],
    pixel_skew,
    menu="<Image>/Filters/Distorts",
    domain=("gimp20-python", gimp.locale_directory)
    )

main()