Section 12.5. PyDraw: Painting and Moving Graphics


12.5. PyDraw: Painting and Moving Graphics

Chapter 10 introduced simple Tkinter animation techniques (see the tour's canvasDraw variants). The PyDraw program listed here builds upon those ideas to implement a more feature-rich painting program in Python. It adds new trails and scribble drawing modes, object and background color fills, embedded photos, and more. In addition, it implements object movement and animation techniquesdrawn objects may be moved around the canvas by clicking and dragging, and any drawn object can be gradually moved across the screen to a target location clicked with the mouse.

12.5.1. Running PyDraw

PyDraw is essentially a Tkinter canvas with lots of keyboard and mouse event bindings to allow users to perform common drawing operations. This isn't a professional-grade paint program by any definition, but it's fun to play with. In fact, you really shouldit is impossible to capture things such as object motion in the medium afforded by this book. Start PyDraw from the launcher bars (or run the file movingpics.py from Example 12-8 directly). Press the ? key to view a help message giving available commands (or read the help string in the code listings).

Figure 12-13 shows PyDraw after a few objects have been drawn on the canvas. To move any object shown here, either click it with the middle mouse button and drag to move it with the mouse cursor, or middle-click the object, and then right-click in the spot you want it to move toward. In the latter case, PyDraw performs an animated (gradual) movement of the object to the target spot. Try this on the picture of Python creator Guido van Rossum, shown near the top of the figure, to start the famous "Moving Guido Demo" (yes, he has a sense of humor too).

Figure 12-13. PyDraw with draw objects ready to be moved


Press "p" to insert photos, and use left-button drags to draw shapes. (Note to Windows users: middle-click is usually both mouse buttons at once, but you may need to configure this in your control panel.) In addition to mouse events, there are 17 key-press commands for tailoring sketches that I won't cover here. It takes a while to get the hang of what all the keyboard and mouse commands do; but once you've mastered the bindings, you too can begin generating senseless electronic artwork such as that in Figure 12-14.

Figure 12-14. PyDraw after substantial play


12.5.2. PyDraw Source Code

Like PyEdit, PyDraw lives in a single file. Two extensions that customize motion implementations are listed following the main module shown in Example 12-8.

Example 12-8. PP3E\Gui\MovingPics\movingpics.py

 ############################################################################## # PyDraw: simple canvas paint program and object mover/animator # uses time.sleep loops to implement object move loops, such that only # one move can be in progress at once; this is smooth and fast, but see # the widget.after and thread-based subclasses here for other techniques; ############################################################################## helpstr = """--PyDraw version 1.0-- Mouse commands:   Left        = Set target spot   Left+Move   = Draw new object   Double Left = Clear all objects   Right       = Move current object   Middle      = Select closest object   Middle+Move = Drag current object Keyboard commands:   w=Pick border width  c=Pick color   u=Pick move unit     s=Pick move delay   o=Draw ovals         r=Draw rectangles   l=Draw lines         a=Draw arcs   d=Delete object      1=Raise object   2=Lower object       f=Fill object   b=Fill background    p=Add photo   z=Save postscript    x=Pick pen modes   ?=Help               other=clear text """ import time, sys from Tkinter import * from tkFileDialog import * from tkMessageBox import * PicDir = '../gifs' if sys.platform[:3] == 'win':     HelpFont = ('courier', 9, 'normal') else:     HelpFont = ('courier', 12, 'normal') pickDelays = [0.01, 0.025, 0.05, 0.10, 0.25, 0.0, 0.001, 0.005] pickUnits  = [1, 2, 4, 6, 8, 10, 12] pickWidths = [1, 2, 5, 10, 20] pickFills  = [None,'white','blue','red','black','yellow','green','purple'] pickPens   = ['elastic', 'scribble', 'trails'] class MovingPics:     def _ _init_ _(self, parent=None):         canvas = Canvas(parent, width=500, height=500, bg= 'white')         canvas.pack(expand=YES, fill=BOTH)         canvas.bind('<ButtonPress-1>',  self.onStart)         canvas.bind('<B1-Motion>',      self.onGrow)         canvas.bind('<Double-1>',       self.onClear)         canvas.bind('<ButtonPress-3>',  self.onMove)         canvas.bind('<Button-2>',       self.onSelect)         canvas.bind('<B2-Motion>',      self.onDrag)         parent.bind('<KeyPress>',       self.onOptions)         self.createMethod = Canvas.create_oval         self.canvas = canvas         self.moving = []         self.images = []         self.object = None         self.where  = None         self.scribbleMode = 0         parent.title('PyDraw - Moving Pictures 1.0')         parent.protocol('WM_DELETE_WINDOW', self.onQuit)         self.realquit = parent.quit         self.textInfo = self.canvas.create_text(                                  5, 5, anchor=NW,                                  font=HelpFont,                                  text='Press ? for help')     def onStart(self, event):         self.where  = event         self.object = None     def onGrow(self, event):         canvas = event.widget         if self.object and pickPens[0] == 'elastic':             canvas.delete(self.object)         self.object = self.createMethod(canvas,                                 self.where.x, self.where.y,    # start                                 event.x, event.y,              # stop                                 fill=pickFills[0], width=pickWidths[0])         if pickPens[0] == 'scribble':             self.where = event  # from here next time     def onClear(self, event):         if self.moving: return       # ok if moving but confusing         event.widget.delete('all')   # use all tag         self.images = []         self.textInfo = self.canvas.create_text(                                  5, 5, anchor=NW,                                  font=HelpFont,                                  text='Press ? for help')     def plotMoves(self, event):         diffX  = event.x - self.where.x              # plan animated moves         diffY  = event.y - self.where.y              # horizontal then vertical         reptX  = abs(diffX) / pickUnits[0]           # incr per move, number moves         reptY  = abs(diffY) / pickUnits[0]           # from last to event click         incrX  = pickUnits[0] * ((diffX > 0) or -1)         incrY  = pickUnits[0] * ((diffY > 0) or -1)         return incrX, reptX, incrY, reptY     def onMove(self, event):         traceEvent('onMove', event, 0)               # move current object to click         object = self.object                         # ignore some ops during mv         if object and object not in self.moving:             msecs  = int(pickDelays[0] * 1000)             parms  = 'Delay=%d msec, Units=%d' % (msecs, pickUnits[0])             self.setTextInfo(parms)             self.moving.append(object)             canvas = event.widget             incrX, reptX, incrY, reptY = self.plotMoves(event)             for i in range(reptX):                 canvas.move(object, incrX, 0)                 canvas.update( )                 time.sleep(pickDelays[0])             for i in range(reptY):                 canvas.move(object, 0, incrY)                 canvas.update( )                      # update runs other ops                 time.sleep(pickDelays[0])             # sleep until next move             self.moving.remove(object)             if self.object == object: self.where  = event     def onSelect(self, event):         self.where  = event         self.object = self.canvas.find_closest(event.x, event.y)[0]   # tuple     def onDrag(self, event):         diffX = event.x - self.where.x                # OK if object in moving         diffY = event.y - self.where.y                # throws it off course         self.canvas.move(self.object, diffX, diffY)         self.where = event     def onOptions(self, event):         keymap = {             'w': lambda self: self.changeOption(pickWidths, 'Pen Width'),             'c': lambda self: self.changeOption(pickFills,  'Color'),             'u': lambda self: self.changeOption(pickUnits,  'Move Unit'),             's': lambda self: self.changeOption(pickDelays, 'Move Delay'),             'x': lambda self: self.changeOption(pickPens,   'Pen Mode'),             'o': lambda self: self.changeDraw(Canvas.create_oval,      'Oval'),             'r': lambda self: self.changeDraw(Canvas.create_rectangle, 'Rect'),             'l': lambda self: self.changeDraw(Canvas.create_line,      'Line'),             'a': lambda self: self.changeDraw(Canvas.create_arc,       'Arc'),             'd': MovingPics.deleteObject,             '1': MovingPics.raiseObject,             '2': MovingPics.lowerObject,        # if only 1 call pattern             'f': MovingPics.fillObject,         # use unbound method objects             'b': MovingPics.fillBackground,     # else lambda passed self             'p': MovingPics.addPhotoItem,             'z': MovingPics.savePostscript,             '?': MovingPics.help}         try:             keymap[event.char](self)         except KeyError:             self.setTextInfo('Press ? for help')     def changeDraw(self, method, name):         self.createMethod = method              # unbound Canvas method         self.setTextInfo('Draw Object=' + name)     def changeOption(self, list, name):         list.append(list[0])         del list[0]         self.setTextInfo('%s=%s' % (name, list[0]))     def deleteObject(self):         if self.object != self.textInfo:        # ok if object in moving             self.canvas.delete(self.object)     # erases but move goes on             self.object = None     def raiseObject(self):         if self.object:                         # ok if moving             self.canvas.tkraise(self.object)    # raises while moving     def lowerObject(self):         if self.object:             self.canvas.lower(self.object)     def fillObject(self):         if self.object:             type = self.canvas.type(self.object)             if type == 'image':                 pass             elif type == 'text':                 self.canvas.itemconfig(self.object, fill=pickFills[0])             else:                 self.canvas.itemconfig(self.object,                                fill=pickFills[0], width=pickWidths[0])     def fillBackground(self):         self.canvas.config(bg=pickFills[0])     def addPhotoItem(self):         if not self.where: return         filetypes=[('Gif files', '.gif'), ('All files', '*')]         file = askopenfilename(initialdir=PicDir, filetypes=filetypes)         if file:             image = PhotoImage(file=file)                     # load image             self.images.append(image)                         # keep reference             self.object = self.canvas.create_image(           # add to canvas                                  self.where.x, self.where.y,  # at last spot                                  image=image, anchor=NW)     def savePostscript(self):         file = asksaveasfilename( )         if file:             self.canvas.postscript(file=file)  # save canvas to file     def help(self):         self.setTextInfo(helpstr)         #showinfo('PyDraw', helpstr)     def setTextInfo(self, text):         self.canvas.dchars(self.textInfo, 0, END)         self.canvas.insert(self.textInfo, 0, text)         self.canvas.tkraise(self.textInfo)     def onQuit(self):         if self.moving:             self.setTextInfo("Can't quit while move in progress")         else:             self.realquit( )  # std wm delete: err msg if move in progress def traceEvent(label, event, fullTrace=1):     print label     if fullTrace:         for key in dir(event): print key, '=>', getattr(event, key) if _ _name_ _ == '_ _main_ _':     from sys import argv                        # when this file is executed     if len(argv) == 2: PicDir = argv[1]         # '..' fails if run elsewhere     root = Tk( )                                # make, run a MovingPics object     MovingPics(root)     root.mainloop( ) 

Just as in Chapter 10's canvasDraw examples, we can add support for moving more than one object at the same time with either after scheduled callback events or threads. Example 12-9 shows a MovingPics subclass that codes the necessary customizations to do parallel moves with after events. Run this file directly to see the difference; I could try to capture the notion of multiple objects in motion with a screenshot, but I would almost certainly fail.

Example 12-9. PP3E\Gui\MovingPics\movingpics_after.py

 ############################################################################## # PyDraw-after: simple canvas paint program and object mover/animator # use widget.after scheduled events to implement object move loops, such # that more than one can be in motion at once without having to use threads; # this does moves in parallel, but seems to be slower than time.sleep version; # see also canvasDraw in Tour: builds and passes the incX/incY list at once: # here, would be allmoves = ([(incrX, 0)] * reptX) + ([(0, incrY)] * reptY) ############################################################################## from movingpics import * class MovingPicsAfter(MovingPics):     def doMoves(self, delay, objectId, incrX, reptX, incrY, reptY):         if reptX:             self.canvas.move(objectId, incrX, 0)             reptX -= 1         else:             self.canvas.move(objectId, 0, incrY)             reptY -= 1         if not (reptX or reptY):             self.moving.remove(objectId)         else:             self.canvas.after(delay,                 self.doMoves, delay, objectId, incrX, reptX, incrY, reptY)     def onMove(self, event):         traceEvent('onMove', event, 0)         object = self.object                      # move cur obj to click spot         if object:             msecs  = int(pickDelays[0] * 1000)             parms  = 'Delay=%d msec, Units=%d' % (msecs, pickUnits[0])             self.setTextInfo(parms)             self.moving.append(object)             incrX, reptX, incrY, reptY = self.plotMoves(event)             self.doMoves(msecs, object, incrX, reptX, incrY, reptY)             self.where = event if _ _name_ _ == '_ _main_ _':     from sys import argv                          # when this file is executed     if len(argv) == 2:         import movingpics                         # not this module's global         movingpics.PicDir = argv[1]               # and from* doesn't link names     root = Tk( )     MovingPicsAfter(root)     root.mainloop( ) 

Now, while one or more moves are in progress, you can start another by middle-clicking on another object and right-clicking on the spot to which you want it to move. It starts its journey immediately, even if other objects are in motion. Each object's scheduled after events are added to the same event loop queue and dispatched by Tkinter as soon as possible after a timer expiration. If you run this subclass module directly, you'll probably notice that movement isn't quite as fast or as smooth as in the original, but multiple moves can overlap in time.

Example 12-10 shows how to achieve such parallelism with threads. This process works, but as we learned in Chapters 10 and 11, updating GUIs in spawned threads is generally a dangerous affair. On my machine, the movement that this script implements with threads is a bit jerkier than the original versiona reflection of the overhead incurred for switching the interpreter (and CPU) between multiple threads.

Example 12-10. PP3E\Gui\MovingPics\movingpics_threads.py

 ################################################################### # use threads to move objects; seems to work on Windows provided # that canvas.update( ) not called by threads(else exits with fatal # errors, some objs start moving immediately after drawn, etc.); # at least some canvas method calls must be thread safe in Tkinter; # this is less smooth than time.sleep, and is dangerous in general: # threads are best coded to update global vars, not change GUI; ################################################################### import thread, time, sys, random from Tkinter import Tk, mainloop from movingpics import MovingPics, pickUnits, pickDelays class MovingPicsThreaded(MovingPics):     def _ _init_ _(self, parent=None):         MovingPics._ _init_ _(self, parent)         self.mutex = thread.allocate_lock( )         import sys         #sys.setcheckinterval(0) # switch after each vm op- doesn't help     def onMove(self, event):         object = self.object         if object and object not in self.moving:             msecs  = int(pickDelays[0] * 1000)             parms  = 'Delay=%d msec, Units=%d' % (msecs, pickUnits[0])             self.setTextInfo(parms)             #self.mutex.acquire( )             self.moving.append(object)             #self.mutex.release( )             thread.start_new_thread(self.doMove, (object, event))     def doMove(self, object, event):         canvas = event.widget         incrX, reptX, incrY, reptY = self.plotMoves(event)         for i in range(reptX):             canvas.move(object, incrX, 0)             # canvas.update( )             time.sleep(pickDelays[0])         # this can change         for i in range(reptY):             canvas.move(object, 0, incrY)             # canvas.update( )                 # update runs other ops             time.sleep(pickDelays[0])           # sleep until next move         #self.mutex.acquire( )         self.moving.remove(object)         if self.object == object: self.where  = event         #self.mutex.release( ) if _ _name_ _ == '_ _main_ _':     root = Tk( )     MovingPicsThreaded(root)     mainloop( ) 




Programming Python
Programming Python
ISBN: 0596009259
EAN: 2147483647
Year: 2004
Pages: 270
Authors: Mark Lutz

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