image.py

# Copyright 2014 Christoph Reiter
#
# 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 2 of the License, or
# (at your option) any later version.

"""Some helper function for loading and converting image data."""

import math
from typing import Optional

from gi.repository import GdkPixbuf, Gtk, Gdk, GLib
import cairo


def get_surface_for_pixbuf(widget: Gtk.Widget, pixbuf: Optional[GdkPixbuf.Pixbuf])\
        -> Optional[cairo.Surface]:
    """:returns: a cairo surface, if possible"""
    if not pixbuf:
        return None
    scale_factor = widget.get_scale_factor()
    return Gdk.cairo_surface_create_from_pixbuf(
            pixbuf, scale_factor, widget.get_window())


def get_surface_extents(surface):
    """Gives (x, y, width, height) for a surface, scale independent"""

    ctx = cairo.Context(surface)
    x1, y1, x2, y2 = ctx.clip_extents()
    x1 = int(math.floor(x1))
    y1 = int(math.floor(y1))
    x2 = int(math.ceil(x2))
    y2 = int(math.ceil(y2))
    x2 -= x1
    y2 -= y1

    return (x1, y1, x2, y2)


def get_border_radius(_widgets=[]):
    """Returns the border radius commonly used in the current theme.
    If there are no rounded corners 0 will be returned.
    """

    if not _widgets:
        b = Gtk.Button()
        b.show()
        e = Gtk.Entry()
        e.show()
        _widgets += [b, e]

    radii = []
    for widget in _widgets:
        style_context = widget.get_style_context()
        radii.append(style_context.get_property(
            Gtk.STYLE_PROPERTY_BORDER_RADIUS, style_context.get_state()))
    radius = max(radii)

    # Doesn't work on the default Ubuntu theme.
    # Not sure why, so fix manually for now
    theme_name = Gtk.Settings.get_default().props.gtk_theme_name
    if theme_name in ("Ambiance", "Radiance"):
        radius = int(radius / 1.5)

    return radius


def add_border(pixbuf, color, width=1, radius=0):
    """Add a border to the pixbuf and round of the edges.
    color is a Gdk.RGBA
    The resulting pixbuf will be width * 2px higher and wider.

    Can not fail.
    """

    w, h = pixbuf.get_width(), pixbuf.get_height()
    w += width * 2
    h += width * 2
    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, w, h)
    ctx = cairo.Context(surface)

    pi = math.pi
    r = min(radius, min(w, h) / 2)
    ctx.new_path()
    ctx.arc(w - r, r, r, -pi / 2, 0)
    ctx.arc(w - r, h - r, r, 0, pi / 2)
    ctx.arc(r, h - r, r, pi / 2, pi)
    ctx.arc(r, r, r, pi, pi * 3 / 2)
    ctx.close_path()

    Gdk.cairo_set_source_pixbuf(ctx, pixbuf, width, width)
    ctx.clip_preserve()
    ctx.paint()

    ctx.set_source_rgba(color.red, color.green, color.blue, color.alpha)
    ctx.set_line_width(width * 2)
    ctx.stroke()

    return Gdk.pixbuf_get_from_surface(surface, 0, 0, w, h)


def add_border_widget(pixbuf, widget):
    """Like add_border() but uses the widget to get a border color and a
    border width.
    """

    context = widget.get_style_context()
    color = context.get_color(context.get_state())
    color.alpha *= 0.1
    scale_factor = widget.get_scale_factor()
    border_radius = get_border_radius() * scale_factor

    return add_border(pixbuf, color, width=scale_factor, radius=border_radius)


def scale(pixbuf, boundary, scale_up=True, force_copy=False):
    """Scale a pixbuf so it fits into the boundary.
    (preserves image aspect ratio)

    If `scale_up` is True, the resulting pixbuf can be larger than
    the original one.

    If `force_copy` is False the resulting pixbuf might be the passed one.

    Can not fail.
    """

    size = pixbuf.get_width(), pixbuf.get_height()

    scale_w, scale_h = calc_scale_size(boundary, size, scale_up)

    if (scale_w, scale_h) == size:
        if force_copy:
            return pixbuf.copy()
        return pixbuf

    return pixbuf.scale_simple(scale_w, scale_h, GdkPixbuf.InterpType.BILINEAR)


def calc_scale_size(boundary, size, scale_up=True):
    """Returns the biggest possible size to fit into the boundary,
    respecting the aspect ratio.

    If `scale_up` is True the result can be larger than size.

    All sizes have to be > 0.
    """

    bwidth, bheight = boundary
    iwidth, iheight = size

    if bwidth <= 0 or bheight <= 0 or iwidth <= 0 or iheight <= 0:
        raise ValueError

    scale_w, scale_h = iwidth, iheight

    if iwidth > bwidth or iheight > bheight or scale_up:
        bratio = float(bwidth) / bheight
        iratio = float(iwidth) / iheight

        if iratio > bratio:
            scale_w = bwidth
            scale_h = int(bwidth / iratio)
        else:
            scale_w = int(bheight * iratio)
            scale_h = bheight

    return scale_w, scale_h


def pixbuf_from_file(fileobj, boundary, scale_factor=1):
    """Returns a pixbuf with the maximum size defined by boundary.

    Can raise GLib.GError and return None
    """

    try:
        pixbuf = GdkPixbuf.Pixbuf.new_from_file(fileobj.name)
    except GLib.GError:
        try:
            loader = GdkPixbuf.PixbufLoader()
            loader.write(fileobj.read())
            loader.close()
            fileobj.seek(0, 0)
            pixbuf = loader.get_pixbuf()
        except EnvironmentError:
            return

    w, h = boundary
    w *= scale_factor
    h *= scale_factor

    return scale(pixbuf, (w, h), scale_up=True)