combine_svg.py

"""
based on https://neuroscience.telenczuk.pl/?p=331
"""

import svgutils.transform as sg


class Svg(object):
    "svg files with a data object (the svg), width, height and coordinates"

    def __init__(self, data, dim, coords):
        self.data = data
        self.width = dim[0]
        self.height = dim[1]
        self.x = coords[0]
        self.y = coords[1]

    def scale_width_to_reference(self, reference_width):
        """Proportionally scale the image to a given width."""
        scalings_factor = reference_width / self.width
        self.data.moveto(0, 0, scale=scalings_factor)
        self.width = self.width * scalings_factor
        self.height = self.height * scalings_factor

    def scale_by_factor(self, scalings_factor):
        """Proportionally scale image by a scaling factor."""
        self.data.moveto(0, 0, scale=scalings_factor)
        self.width = self.width * scalings_factor
        self.height = self.height * scalings_factor

    def move(self, x, y):
        """Move the coordinates of an image."""
        self.data.moveto(x, y)
        self.x = x
        self.y = y


def get_size(svg_file):
    """Naively parse the svg text file to get the width and height."""
    with open(svg_file) as svg:
        for line in svg:
            if line.startswith('<svg'):
                paramdict = {e.split('="')[0]: e.split('="')[1] for e in line[5:-2].split('" ')}
                break
    return int(paramdict["width"].replace('pt', '')), int(paramdict["height"].replace('pt', ''))


def rescale(svgs):
    """Change the dimensions of the images to the desired combinations."""
    svgs['B'].scale_width_to_reference(svgs['A'].width)
    svgs['C'].scale_width_to_reference(svgs['A'].width)
    svgs['D'].scale_width_to_reference(svgs['A'].width)
    assert svgs['A'].width == svgs['B'].width == svgs['C'].width == svgs['D'].width

    svgs['E'].scale_width_to_reference(svgs['F'].width)
    assert svgs['E'].width == svgs['F'].width

    left_height = sum([svgs[i].height for i in ['A', 'B', 'C', 'D']])
    right_height = sum([svgs[i].height for i in ['E', 'F', ]])
    scalings_factor = right_height / left_height
    svgs['A'].scale_by_factor(scalings_factor)
    svgs['B'].scale_by_factor(scalings_factor)
    svgs['C'].scale_by_factor(scalings_factor)
    svgs['D'].scale_by_factor(scalings_factor)
    assert sum([svgs[i].height for i in ['A', 'B', 'C', 'D']]
               ) == sum([svgs[i].height for i in ['E', 'F', ]])


def change_positions(svgs):
    """Move the images to the desired positions."""
    svgs['B'].move(0, svgs['A'].height)
    svgs['C'].move(0, svgs['A'].height + svgs['B'].height)
    svgs['D'].move(0, svgs['A'].height + svgs['B'].height + svgs['C'].height)
    svgs['E'].move(svgs['A'].width, 0)
    svgs['F'].move(svgs['A'].width, svgs['E'].height)


def letter_annotations(svgs):
    """Add letters based on the location of the images."""
    return [sg.TextElement(value.x + 10, value.y + 15, key, size=15, weight="bold")
            for key, value in svgs.items()]


def files_to_svg_dict(files):
    """Convert a list of images to a dictionary.

    Mapping the image basename to the Svg class instance,
    setting the dimensions based on sizes and coordinates (0,0) by default
    """
    return {
        s.split('.')[0]: Svg(
            data=sg.fromfile(s).getroot(),
            dim=get_size(s),
            coords=(0, 0))
        for s in files}


def main():
    svgs = files_to_svg_dict(["A.svg", "B.svg", "C.svg", "D.svg", "E.svg", "F.svg"])
    rescale(svgs)
    change_positions(svgs)
    full_width = sum([svgs[i].width for i in ['A', 'E']])
    full_height = sum([svgs[i].height for i in ['A', 'B', 'C', 'D']])
    fig = sg.SVGFigure(full_width, full_height)
    text = letter_annotations(svgs)
    fig.append([s.data for s in svgs.values()])
    fig.append(text)
    fig.save("combined.svg")


if __name__ == '__main__':
    main()