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Touch Tracer Line Drawing Demonstration

pic26

This demonstrates tracking each touch registered to a device. You should see a basic background image. When you press and hold the mouse, you should see cross-hairs with the coordinates written next to them. As you drag, it leaves a trail. Additional information, like pressure, will be shown if they are in your device’s touch.profile.

Note

A function calculate_points handling the points which will be drawn has by default implemented a delay of 5 steps. To get more precise visual results lower the value of the optional keyword argument steps.

This program specifies an icon, the file icon.png, in its App subclass. It also uses the particle.png file as the source for drawing the trails which are white on transparent. The file touchtracer.kv describes the application.

The file android.txt is used to package the application for use with the Kivy Launcher Android application. For Android devices, you can copy/paste this directory into /sdcard/kivy/touchtracer on your Android device.

File demo/touchtracer/main.py

'''
Touch Tracer Line Drawing Demonstration
=======================================

This demonstrates tracking each touch registered to a device. You should
see a basic background image. When you press and hold the mouse, you
should see cross-hairs with the coordinates written next to them. As
you drag, it leaves a trail. Additional information, like pressure,
will be shown if they are in your device's touch.profile.

.. note::

   A function `calculate_points` handling the points which will be drawn
   has by default implemented a delay of 5 steps. To get more precise visual
   results lower the value of the optional keyword argument `steps`.

This program specifies an icon, the file icon.png, in its App subclass.
It also uses the particle.png file as the source for drawing the trails which
are white on transparent. The file touchtracer.kv describes the application.

The file android.txt is used to package the application for use with the
Kivy Launcher Android application. For Android devices, you can
copy/paste this directory into /sdcard/kivy/touchtracer on your Android device.

'''
__version__ = '1.0'

import kivy
kivy.require('1.0.6')

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.label import Label
from kivy.graphics import Color, Rectangle, Point, GraphicException
from random import random
from math import sqrt


def calculate_points(x1, y1, x2, y2, steps=5):
    dx = x2 - x1
    dy = y2 - y1
    dist = sqrt(dx * dx + dy * dy)
    if dist < steps:
        return
    o = []
    m = dist / steps
    for i in range(1, int(m)):
        mi = i / m
        lastx = x1 + dx * mi
        lasty = y1 + dy * mi
        o.extend([lastx, lasty])
    return o


class Touchtracer(FloatLayout):

    def on_touch_down(self, touch):
        win = self.get_parent_window()
        ud = touch.ud
        ud['group'] = g = str(touch.uid)
        pointsize = 5
        if 'pressure' in touch.profile:
            ud['pressure'] = touch.pressure
            pointsize = (touch.pressure * 100000) ** 2
        ud['color'] = random()

        with self.canvas:
            Color(ud['color'], 1, 1, mode='hsv', group=g)
            ud['lines'] = [
                Rectangle(pos=(touch.x, 0), size=(1, win.height), group=g),
                Rectangle(pos=(0, touch.y), size=(win.width, 1), group=g),
                Point(points=(touch.x, touch.y), source='particle.png',
                      pointsize=pointsize, group=g)]

        ud['label'] = Label(size_hint=(None, None))
        self.update_touch_label(ud['label'], touch)
        self.add_widget(ud['label'])
        touch.grab(self)
        return True

    def on_touch_move(self, touch):
        if touch.grab_current is not self:
            return
        ud = touch.ud
        ud['lines'][0].pos = touch.x, 0
        ud['lines'][1].pos = 0, touch.y

        index = -1

        while True:
            try:
                points = ud['lines'][index].points
                oldx, oldy = points[-2], points[-1]
                break
            except:
                index -= 1

        points = calculate_points(oldx, oldy, touch.x, touch.y)

        # if pressure changed create a new point instruction
        if 'pressure' in ud:
            if not .95 < (touch.pressure / ud['pressure']) < 1.05:
                g = ud['group']
                pointsize = (touch.pressure * 100000) ** 2
                with self.canvas:
                    Color(ud['color'], 1, 1, mode='hsv', group=g)
                    ud['lines'].append(
                        Point(points=(), source='particle.png',
                              pointsize=pointsize, group=g))

        if points:
            try:
                lp = ud['lines'][-1].add_point
                for idx in range(0, len(points), 2):
                    lp(points[idx], points[idx + 1])
            except GraphicException:
                pass

        ud['label'].pos = touch.pos
        import time
        t = int(time.time())
        if t not in ud:
            ud[t] = 1
        else:
            ud[t] += 1
        self.update_touch_label(ud['label'], touch)

    def on_touch_up(self, touch):
        if touch.grab_current is not self:
            return
        touch.ungrab(self)
        ud = touch.ud
        self.canvas.remove_group(ud['group'])
        self.remove_widget(ud['label'])

    def update_touch_label(self, label, touch):
        label.text = 'ID: %s\nPos: (%d, %d)\nClass: %s' % (
            touch.id, touch.x, touch.y, touch.__class__.__name__)
        label.texture_update()
        label.pos = touch.pos
        label.size = label.texture_size[0] + 20, label.texture_size[1] + 20


class TouchtracerApp(App):
    title = 'Touchtracer'
    icon = 'icon.png'

    def build(self):
        return Touchtracer()

    def on_pause(self):
        return True


if __name__ == '__main__':
    TouchtracerApp().run()

Image demo/touchtracer/icon.png

../_images/icon.png

File demo/touchtracer/touchtracer.kv

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#:kivy 1.0
#:import kivy kivy

<Touchtracer>:
    canvas:
        Color:
            rgb: 1, 1, 1
        Rectangle:
            source: 'data/images/background.jpg'
            size: self.size

    BoxLayout:
        padding: '10dp'
        spacing: '10dp'
        size_hint: 1, None
        pos_hint: {'top': 1}
        height: '44dp'
        Image:
            size_hint: None, None
            size: '24dp', '24dp'
            source: 'data/logo/kivy-icon-64.png'
            mipmap: True
        Label:
            height: '24dp'
            text_size: self.width, None
            color: (1, 1, 1, .8)
            text: 'Kivy %s - Touchtracer' % kivy.__version__
            valign: 'middle'

File demo/touchtracer/android.txt

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title=Touchtracer
author=Kivy team
orientation=landscape