imageview.py

# Copyright (C) 2008, One Laptop per Child
# Author: Sayamindu Dasgupta <sayamindu@laptop.org>
#
# 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.
#
# 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.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
#
# From ImageViewer Activity - file ImageView.py

import cairo
import math

from gi.repository import GLib
from gi.repository import Gtk
from gi.repository import Gdk
from gi.repository import GdkPixbuf
from gi.repository import GObject
from gi.repository import Gio

ZOOM_STEP = 0.05
ZOOM_MAX = 10
ZOOM_MIN = 0.05


def pixbuf_from_data(data):
    stream = Gio.MemoryInputStream.new_from_data(data, None)
    pixbuf = GdkPixbuf.Pixbuf.new_from_stream(stream, None)
    return pixbuf


def _surface_from_data(data, ctx):
    pixbuf = pixbuf_from_data(data)
    surface = ctx.get_target().create_similar(
        cairo.CONTENT_COLOR_ALPHA, pixbuf.get_width(),
        pixbuf.get_height())

    ctx_surface = cairo.Context(surface)
    Gdk.cairo_set_source_pixbuf(ctx_surface, pixbuf, 0, 0)
    ctx_surface.paint()
    return surface


def _rotate_surface(surface, direction):
    ctx = cairo.Context(surface)
    new_surface = ctx.get_target().create_similar(
        cairo.CONTENT_COLOR_ALPHA, surface.get_height(),
        surface.get_width())

    ctx_surface = cairo.Context(new_surface)

    if direction == 1:
        ctx_surface.translate(surface.get_height(), 0)
    else:
        ctx_surface.translate(0, surface.get_width())

    ctx_surface.rotate(math.pi / 2 * direction)

    ctx_surface.set_source_surface(surface, 0, 0)
    ctx_surface.paint()

    return new_surface


def _flip_surface(surface):
    ctx = cairo.Context(surface)
    new_surface = ctx.get_target().create_similar(
        cairo.CONTENT_COLOR_ALPHA, surface.get_width(),
        surface.get_height())

    ctx_surface = cairo.Context(new_surface)
    ctx_surface.rotate(math.pi)
    ctx_surface.translate(-surface.get_width(), -surface.get_height())

    ctx_surface.set_source_surface(surface, 0, 0)
    ctx_surface.paint()

    return new_surface


class ImageViewer(Gtk.DrawingArea, Gtk.Scrollable):
    __gtype_name__ = 'ImageViewer'

    __gproperties__ = {
        "hscroll-policy": (Gtk.ScrollablePolicy, "hscroll-policy",
                           "hscroll-policy", Gtk.ScrollablePolicy.MINIMUM,
                           GObject.ParamFlags.READWRITE),
        "hadjustment": (Gtk.Adjustment, "hadjustment", "hadjustment",
                        GObject.ParamFlags.READWRITE),
        "vscroll-policy": (Gtk.ScrollablePolicy, "hscroll-policy",
                           "hscroll-policy", Gtk.ScrollablePolicy.MINIMUM,
                           GObject.ParamFlags.READWRITE),
        "vadjustment": (Gtk.Adjustment, "hadjustment", "hadjustment",
                        GObject.ParamFlags.READWRITE),
    }

    __gsignals__ = {
        'setup-new-surface': (GObject.SignalFlags.RUN_FIRST, GObject.TYPE_NONE,
                              ([])),
    }

    def __init__(self):
        Gtk.DrawingArea.__init__(self)

        self._data = None
        self._data_changed = False
        self._surface = None
        self._zoom = None
        self._target_point = None
        self._anchor_point = None

        self._in_dragtouch = False
        self._in_zoomtouch = False
        self._zoomtouch_scale = 1

        self._in_scrolling = False
        self._scrolling_hid = None
        self._hadj = None
        self._vadj = None
        self._hadj_value_changed_hid = None
        self._vadj_value_changed_hid = None

        self.connect('draw', self.__draw_cb)

    def set_data(self, data):
        self._data = data
        self._data_changed = True
        self.queue_draw()

    def do_get_property(self, prop):
        # We don't use the getter but GTK wants it defined as we are
        # implementing Gtk.Scrollable interface.
        pass

    def do_set_property(self, prop, value):
        # The scrolled window will give us the adjustments.  Make a
        # reference to them and also connect to their value-changed
        # signal.
        if prop.name == 'hadjustment':
            if value is not None:
                hadj = value
                self._hadj_value_changed_hid = \
                    hadj.connect('value-changed', self.__hadj_value_changed_cb)
                self._hadj = hadj

        elif prop.name == 'vadjustment':
            if value is not None:
                vadj = value
                self._vadj_value_changed_hid = \
                    vadj.connect('value-changed', self.__vadj_value_changed_cb)
                self._vadj = vadj

    def update_adjustments(self):
        alloc = self.get_allocation()
        scaled_width = self._surface.get_width() * self._zoom
        scaled_height = self._surface.get_height() * self._zoom

        page_size_x = alloc.width * 1.0 / scaled_width
        self._hadj.set_lower(0)
        self._hadj.set_page_size(page_size_x)
        self._hadj.set_upper(1.0)
        self._hadj.set_step_increment(0.1)
        self._hadj.set_page_increment(0.5)

        page_size_y = alloc.height * 1.0 / scaled_height
        self._vadj.set_lower(0)
        self._vadj.set_page_size(page_size_y)
        self._vadj.set_upper(1.0)
        self._vadj.set_step_increment(0.1)
        self._vadj.set_page_increment(0.5)

        anchor_scaled = (self._anchor_point[0] * self._zoom,
                         self._anchor_point[1] * self._zoom)

        # This vector is the top left coordinate of the scaled image.
        scaled_image_topleft = (self._target_point[0] - anchor_scaled[0],
                                self._target_point[1] - anchor_scaled[1])

        max_topleft = (scaled_width - alloc.width,
                       scaled_height - alloc.height)

        max_value = (1.0 - page_size_x,
                     1.0 - page_size_y)

        # This two linear functions map the topleft corner of the
        # image to the value each adjustment.

        if max_topleft[0] != 0:
            self._hadj.disconnect(self._hadj_value_changed_hid)
            self._hadj.set_value(-1 * max_value[0] *
                                 scaled_image_topleft[0] / max_topleft[0])
            self._hadj_value_changed_hid = \
                self._hadj.connect('value-changed',
                                   self.__hadj_value_changed_cb)

        if max_topleft[1] != 0:
            self._vadj.disconnect(self._vadj_value_changed_hid)
            self._vadj.set_value(-1 * max_value[1] *
                                 scaled_image_topleft[1] / max_topleft[1])
            self._vadj_value_changed_hid = \
                self._vadj.connect('value-changed',
                                   self.__vadj_value_changed_cb)

    def _stop_scrolling(self):
        self._in_scrolling = False
        self.queue_draw()
        return False

    def _start_scrolling(self):
        if not self._in_scrolling:
            self._in_scrolling = True

        # Add or update a timer after which the in_scrolling flag will
        # be set to False.  This is to perform a faster drawing while
        # scrolling.
        if self._scrolling_hid is not None:
            GLib.source_remove(self._scrolling_hid)
        self._scrolling_hid = GLib.timeout_add(200,
                                               self._stop_scrolling)

    def __hadj_value_changed_cb(self, adj):
        alloc = self.get_allocation()
        scaled_width = self._surface.get_width() * self._zoom
        anchor_scaled_x = self._anchor_point[0] * self._zoom
        scaled_image_left = self._target_point[0] - anchor_scaled_x

        max_left = scaled_width - alloc.width
        max_value = 1.0 - adj.get_page_size()
        new_left = -1 * max_left * adj.get_value() / max_value

        delta_x = scaled_image_left - new_left
        self._anchor_point = (self._anchor_point[0] + delta_x,
                              self._anchor_point[1])

        self._start_scrolling()
        self.queue_draw()

    def __vadj_value_changed_cb(self, adj):
        alloc = self.get_allocation()
        scaled_height = self._surface.get_height() * self._zoom
        anchor_scaled_y = self._anchor_point[1] * self._zoom
        scaled_image_top = self._target_point[1] - anchor_scaled_y

        max_top = scaled_height - alloc.height
        max_value = 1.0 - adj.get_page_size()
        new_top = -1 * max_top * adj.get_value() / max_value

        delta_y = scaled_image_top - new_top
        self._anchor_point = (self._anchor_point[0],
                              self._anchor_point[1] + delta_y)

        self._start_scrolling()
        self.queue_draw()

    def _center_target_point(self):
        alloc = self.get_allocation()
        self._target_point = (alloc.width / 2, alloc.height / 2)

    def _center_anchor_point(self):
        self._anchor_point = (self._surface.get_width() / 2,
                              self._surface.get_height() / 2)

    def _center_if_small(self):
        # If at the current size the image surface is smaller than the
        # available space, center it on the canvas.

        alloc = self.get_allocation()

        scaled_width = self._surface.get_width() * self._zoom
        scaled_height = self._surface.get_height() * self._zoom

        if alloc.width >= scaled_width and alloc.height >= scaled_height:
            self._center_target_point()
            self._center_anchor_point()
            self.queue_draw()

    def set_zoom(self, zoom):
        if zoom < ZOOM_MIN or zoom > ZOOM_MAX:
            return
        self._zoom = zoom
        self.queue_draw()

    def get_zoom(self):
        return self._zoom

    def can_zoom_in(self):
        return self._zoom + ZOOM_STEP < ZOOM_MAX
        self.update_adjustments()

    def can_zoom_out(self):
        return self._zoom - ZOOM_STEP > ZOOM_MIN
        self.update_adjustments()

    def zoom_in(self):
        if not self.can_zoom_in():
            return
        self._zoom += ZOOM_STEP
        self.update_adjustments()
        self.queue_draw()

    def zoom_out(self):
        if not self.can_zoom_out():
            return
        self._zoom -= ZOOM_MIN

        self._center_if_small()
        self.update_adjustments()
        self.queue_draw()

    def zoom_to_fit(self):
        # This tries to figure out a best fit model
        # We show it in a fit to screen way

        alloc = self.get_allocation()

        surface_width = self._surface.get_width()
        surface_height = self._surface.get_height()

        self._zoom = min(alloc.width * 1.0 / surface_width,
                         alloc.height * 1.0 / surface_height)

        self._center_target_point()
        self._center_anchor_point()
        self.update_adjustments()
        self.queue_draw()

    def zoom_to_width(self):
        alloc = self.get_allocation()
        surface_width = self._surface.get_width()
        self._zoom = alloc.width * 1.0 / surface_width

        self._center_target_point()
        self._center_anchor_point()
        self.update_adjustments()
        self.queue_draw()

    def zoom_original(self):
        self._zoom = 1
        self._center_if_small()
        self.update_adjustments()
        self.queue_draw()

    def _move_anchor_to_target(self, prev_target_point):
        # Calculate the new anchor point, move it from the previous
        # target to the new one.

        prev_anchor_scaled = (self._anchor_point[0] * self._zoom,
                              self._anchor_point[1] * self._zoom)

        # This vector is the top left coordinate of the scaled image.
        scaled_image_topleft = (prev_target_point[0] - prev_anchor_scaled[0],
                                prev_target_point[1] - prev_anchor_scaled[1])

        anchor_scaled = (self._target_point[0] - scaled_image_topleft[0],
                         self._target_point[1] - scaled_image_topleft[1])

        self._anchor_point = (int(anchor_scaled[0] * 1.0 / self._zoom),
                              int(anchor_scaled[1] * 1.0 / self._zoom))

    def start_dragtouch(self, coords):
        self._in_dragtouch = True

        prev_target_point = self._target_point

        # Set target point to the relative coordinates of this view.
        self._target_point = (coords[1], coords[2])

        self._move_anchor_to_target(prev_target_point)
        self.queue_draw()

    def update_dragtouch(self, coords):
        # Drag touch will be replaced by zoom touch if another finger
        # is placed over the display.  When the user finishes zoom
        # touch, it will probably remove one finger after the other,
        # and this method will be called.  In that probable case, we
        # need to start drag touch again.
        if not self._in_dragtouch:
            self.start_dragtouch(coords)
            return

        self._target_point = (coords[1], coords[2])
        self.update_adjustments()
        self.queue_draw()

    def finish_dragtouch(self, coords):
        self._in_dragtouch = False
        self._center_if_small()
        self.update_adjustments()

    def start_zoomtouch(self, center):
        self._in_zoomtouch = True
        self._zoomtouch_scale = 1

        # Zoom touch replaces drag touch.
        self._in_dragtouch = False

        prev_target_point = self._target_point

        # Set target point to the relative coordinates of this view.
        alloc = self.get_allocation()
        self._target_point = (center[1] - alloc.x, center[2] - alloc.y)

        self._move_anchor_to_target(prev_target_point)
        self.queue_draw()

    def update_zoomtouch(self, center, scale):
        self._zoomtouch_scale = scale

        # Set target point to the relative coordinates of this view.
        alloc = self.get_allocation()
        self._target_point = (center[1] - alloc.x, center[2] - alloc.y)

        self.queue_draw()

    def finish_zoomtouch(self):
        self._in_zoomtouch = False

        # Apply zoom
        self._zoom = self._zoom * self._zoomtouch_scale
        self._zoomtouch_scale = 1

        # Restrict zoom values
        if self._zoom < ZOOM_MIN:
            self._zoom = ZOOM_MIN
        elif self._zoom > ZOOM_MAX:
            self._zoom = ZOOM_MAX

        self._center_if_small()
        self.update_adjustments()
        self.queue_draw()

    def set_rotate(self, rotate):
        if rotate == 0:
            return
        elif rotate in [1, -3]:
            self._surface = _rotate_surface(self._surface, 1)
        elif rotate in [-1, 3]:
            self._surface = _rotate_surface(self._surface, -1)
        else:
            self._surface = _flip_surface(self._surface)

        if rotate > 0:
            for i in range(rotate):
                self._anchor_point = (
                    self._surface.get_width() - self._anchor_point[1],
                    self._anchor_point[0])

        if rotate < 0:
            for i in range(-rotate):
                self._anchor_point = (
                    self._anchor_point[1],
                    self._surface.get_height() - self._anchor_point[0])

        self.update_adjustments()
        self.queue_draw()

    def rotate_anticlockwise(self):
        self._surface = _rotate_surface(self._surface, -1)

        # Recalculate the anchor point to make it relative to the new
        # top left corner.
        self._anchor_point = (
            self._anchor_point[1],
            self._surface.get_height() - self._anchor_point[0])

        self.update_adjustments()
        self.queue_draw()

    def rotate_clockwise(self):
        self._surface = _rotate_surface(self._surface, 1)

        # Recalculate the anchor point to make it relative to the new
        # top left corner.
        self._anchor_point = (
            self._surface.get_width() - self._anchor_point[1],
            self._anchor_point[0])

        self.update_adjustments()
        self.queue_draw()

    def __draw_cb(self, widget, ctx):

        # If the image surface is not set, it reads it from the data  If the
        # data is not set yet, it just returns.
        if self._surface is None or self._data_changed:
            if self._data is None:
                return
            self._surface = _surface_from_data(self._data, ctx)
            self._data_changed = False
            self.emit('setup-new-surface')

        if self._zoom is None:
            self.zoom_to_width()

        # If no target point was set via pinch-to-zoom, default to the
        # center of the screen.
        if self._target_point is None:
            self._center_target_point()

        # If no anchor point was set via pinch-to-zoom, default to the
        # center of the surface.
        if self._anchor_point is None:
            self._center_anchor_point()
            self.update_adjustments()

        ctx.translate(*self._target_point)
        zoom_absolute = self._zoom * self._zoomtouch_scale
        ctx.scale(zoom_absolute, zoom_absolute)

        ctx.translate(self._anchor_point[0] * -1, self._anchor_point[1] * -1)

        ctx.set_source_surface(self._surface, 0, 0)

        # Perform faster draw if the view is zooming or scrolling via
        # mouse or touch.
        if self._in_zoomtouch or self._in_dragtouch or self._in_scrolling:
            ctx.get_source().set_filter(cairo.FILTER_NEAREST)

        ctx.paint()