Resize rectangle

[VDK]

Hi,

I'm working on selecting parts of an image by drawing a rectangle. I want to use the on_touch_down and the on_touch_move events. I took the Simple paint app from the documentation as a starting point. I thought to use on_touch_down to draw a small rectangle; on_touch_move then increases the initial size and should draw a new rectangle with the new size, using the same x, y positions as the initial rectangle. What I've tried so far is this piece of code (it is not a nice piece of code at the moment):

from kivy.app import App

from kivy.uix.widget import Widget

from kivy.graphics import Color, Ellipse, Line, Rectangle

class MyPaintWidget(Widget):

    def on_touch_down(self, touch):

        with self.canvas:

            Color(1, 1, 0)

            self.d = 30.

            self.dd = self.d

            self.xpos = touch.x

            self.ypos = touch.y

            #self.rect = Rectangle(pos=(touch.x - d/2, touch.y - d/2), size=(self.width, self.height))

            Rectangle(pos=(touch.x - self.d / 2, touch.y - self.d / 2), size=(self.d, self.d))

            #touch.ud['line'] = Line(points=(touch.x, touch.y))

    def on_touch_move(self, touch):

    self.dd += 10.

    Rectangle(pos=(self.xpos - self.d / 2, self.ypos - self.d / 2), size=(self.dd, self.dd))

    #touch.ud['line'].points += [touch.x, touch.y]        

class MyPaintApp(App):

    def build(self):

        return MyPaintWidget()

if __name__ == '__main__':

    MyPaintApp().run()

This does not do what I want. I wonder if it is possible to resize a rectangle. Any ideas?

Thanks,

Peter

[ZenCODE]

Yeah, the problem is that you are creating a new rectangle each time. This should help you get started, but not sure what you are trying to do with the sizing? :-)

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics import Color, Ellipse, Line, Rectangle


class MyPaintWidget(Widget):

    def on_touch_down(self, touch):
        with self.canvas:
            Color(1, 1, 0)
            self.d = 30.
            self.dd = self.d
            self.xpos = touch.x
            self.ypos = touch.

y
            self.rect = Rectangle(

                pos=(touch.x - self.d / 2, touch.y - self.d / 2),
                size=(self.d, self.d))

    def on_touch_move(self, touch):
        self.dd += 10.
        # self.rect.pos = (self.xpos - self.d / 2, self.ypos - self.d / 2)
        self.rect.pos = touch.pos
        self.rect.size = (self.dd, self.dd)

[VDK]

Hi ZenCODE,

This was very helpful, thanks. What I try to achieve is to extract part of an image. The rectangle marks the area to be extracted.

Peter

[VDK]

I've got it working the way I had in mind. See the code below.

Peter

import kivy

kivy.require('1.0.6')

from kivy.app import App

from kivy.uix.widget import Widget

from kivy.graphics import Color, Ellipse, Line, Rectangle

from kivy.graphics.instructions import InstructionGroup

class MyPaintWidget(Widget):

def on_touch_down(self, touch):

with self.canvas:

Color(1, 1, 0)

self.w = 1.

self.h = 1.

# Keep starting position and initialize variables to store

# the previous x and y position

self.start_x = self.pr_x = touch.x

self.start_y = self.pr_y = touch.y

         

self.rect = Rectangle(pos=(touch.x, touch.y), size=(self.w, self.h))

def on_touch_move(self, touch):

self.calculate_size(touch)

self.rect.pos = (self.start_x, self.start_y)

self.rect.size = (self.w, self.h)

def calculate_size(self, touch):

if touch.x > self.pr_x:

self.w += touch.x - self.pr_x

self.pr_x = touch.x

if touch.y > self.pr_y:

self.h += touch.y - self.pr_y

self.pr_y = touch.y

if touch.x < self.pr_x:

self.w -= self.pr_x - touch.x 

self.pr_x = touch.x

if touch.y < self.pr_y:

self.h -= self.pr_y - touch.y 

self.pr_y = touch.y

class MyPaintApp(App):

    def build(self):

        return MyPaintWidget()

if __name__ == '__main__':

    MyPaintApp().run() 

[VDK]

I also made a version that uses Line to create a resizable rectangle, see code below.

Peter

import kivy

kivy.require('1.0.6')

from kivy.app import App

from kivy.uix.widget import Widget

from kivy.graphics import Color, Ellipse, Line, Rectangle

from kivy.graphics.instructions import InstructionGroup

class MyPaintWidget(Widget):

def on_touch_down(self, touch):

with self.canvas:

Color(1, 1, 0)

# Keep starting position and initialize variables to store

# the previous x and y position

self.bl_x = touch.x # bottom left

self.bl_y = touch.y

self.br_x = 0 # bottom right

self.br_y = 0

self.ur_x = 0 # upper right

self.ur_y = 0

self.ul_x = 0 # upper left

self.ul_y = 0

         

self.line = Line(points=([self.bl_x, self.bl_y]), width=1)

def on_touch_move(self, touch):

self.calculate_points(touch)

self.line.points = [self.bl_x, self.bl_y, self.br_x, self.br_y,

self.ur_x, self.ur_y,self.ul_x, self.ul_y,

self.bl_x, self.bl_y]

def calculate_points(self, touch):

self.ur_x = touch.x

self.ur_y = touch.y

self.br_x = self.ur_x

self.br_y = self.bl_y

self.ul_x = self.bl_x

self.ul_y = self.ur_y

class MyPaintApp(App):

    def build(self):

        return MyPaintWidget()

if __name__ == '__main__':

    MyPaintApp().run()

On Monday, July 6, 2015 at 9:25:38 PM UTC+2, VDK wrote:

I've got it working the way I had in mind. See the code below.

Peter

(text deleted)