Join Club ShowMeDo to Learn Python!

This series is a part of Club ShowMeDo. Click to learn why you should join our club with a simple monthly subscription.

  • We teach Python and all the cool modules
  • Topics include beginner Python, GUIs, Web and Desktop Apps
  • Long, specially crafted video tutorials just for you
  • Club video tutorials extend our normal Free content
  • Save your time - we've done the research for you
  • Keep your skills up-to-date
  • Learn at your own pace, everything you need is shown to you
  • Over 12 hours of archived material are waiting for you in the club

Name: [002] Ian Ozsvald
Member: 106 months
Authored: 181 videos
Description: I am the co-founder of ShowMeDo (see http://showmedo.com/about), author of `The Screencasting Handbook <http://thescreencastinghandbook.com>`_ and the founder of the professional screencast production company `ProCasts <http://procasts.co.uk>`_: .. image:: http://procasts.co.uk/media/procasts_sma ...

Worked Solution - adding a Mirror function to the Image Viewer [ID:550] (10/14)

in series: Build a wxPython Image Viewer

(Showmedo is undergoing major changes. To report any problems viewing the videos please email us and include browser and OS specifics. Cheers - Kyran.)

First of all we uncomment the Mirror menu code and run the application without defining the OnMirrorImage function - we get an AttributeError exception on the Frame.

Next we create an empty OnMirrorImage function and Enable the menu item in OnOpen after the wx.ID_OK.

Next we use the image's Mirror() function, our ShowBitmap() and the Frame's Refresh() to correctly flip the image.

import os
import wx

MAIN_WINDOW_DEFAULT_SIZE = (300,200)

class Frame(wx.Frame):
    
    def __init__(self, parent, id, title):
        style=wx.DEFAULT_FRAME_STYLE ^ (wx.RESIZE_BORDER) # XOR to remove the resizeable border        
        wx.Frame.__init__(self, parent, id, title=title, size=MAIN_WINDOW_DEFAULT_SIZE, style=style)
        self.Center() # open in the centre of the screen
        self.panel = wx.Panel(self)
        self.panel.SetBackgroundColour('White') # make the background of the window white

        self.CreateMenuBar()
        
        # create a StatusBar and give it 2 columns
        self.statusBar = self.CreateStatusBar()
        self.statusBar.SetFieldsCount(2)
        self.statusBar.SetStatusText('No image specified', 1)
        
        self.bitmap = None # set to None as we refer to it in ShowBitmap before we instantiate it
        
    def CreateMenuBar(self):
        "Create a menu bar with Open, Exit items"
        menuBar = wx.MenuBar()
        # Tell our Frame about this MenuBar
        self.SetMenuBar(menuBar)
        menuFile = wx.Menu()
        menuBar.Append(menuFile, '&File')
        # NOTE on wx ids - they're used everywhere, we don't care about them
        # Used to handle events and other things
        # An id can be -1 or wx.ID_ANY, wx.NewId(), your own id
        # Get the id using object.GetId()
        fileOpenMenuItem = menuFile.Append(-1, '&Open Image', 'Open a picture')
        #print "fileOpenMenuItem.GetId()", fileOpenMenuItem.GetId()
        self.Bind(wx.EVT_MENU, self.OnOpen, fileOpenMenuItem)

        # add a 'mirror' option, disable it for now
        # we add mirrorMenuItem to self so that we can reference it later
        self.mirrorMenuItem = menuFile.Append(-1, '&Mirror Image', 'Mirror the image horizontally')
        self.mirrorMenuItem.Enable(False) # we can't mirror an image until we've loaded one in, so start with 'mirror' disabled
        self.Bind(wx.EVT_MENU, self.OnMirrorImage, self.mirrorMenuItem)
        
        # create a menu item for Exit and bind it to the OnExit function       
        exitMenuItem = menuFile.Append(-1, 'E&xit', 'Exit the viewer')        
        self.Bind(wx.EVT_MENU, self.OnExit, exitMenuItem)
        
        # add a Help menu with an About item
        #menuHelp = wx.Menu()
        #menuBar.Append(menuHelp, '&Help')
        #helpMenuItem = menuHelp.Append(-1, '&About', 'About screen')
        #self.Bind(wx.EVT_MENU, self.OnAbout, helpMenuItem)

    def OnMirrorImage(self, event):
        # ask the Image to mirror itself on the x-axis
        self.image = self.image.Mirror()
        # whilst we mirror it and show it, we haven't yet forced a repaint so we won't see it unless we hide the window
        self.ShowBitmap()
        # now we can ask for a refresh which repaints the image
        self.Refresh()

    def OnOpen(self, event):
        "Open an image file, set title if successful"
        # Create a file-open dialog in the current directory
        
        filters = 'Image files (*.gif;*.png;*.jpg)|*.gif;*.png;*.jpg'
        dlg = wx.FileDialog(self, message="Open an Image...", defaultDir=os.getcwd(), 
                            defaultFile="", wildcard=filters, style=wx.OPEN)
        
        # Call the dialog as a model-dialog so we're required to choose Ok or Cancel
        if dlg.ShowModal() == wx.ID_OK:
            # User has selected something, get the path, set the window's title to the path
            filename = dlg.GetPath()
            self.SetTitle(filename)
            wx.BeginBusyCursor()            
            # load the image from the filename
            self.image = wx.Image(filename, wx.BITMAP_TYPE_ANY, -1) # auto-detect file type        
            # set the StatusBar to show the image's size
            self.statusBar.SetStatusText('Size = %s' % (str(self.image.GetSize())) , 1)
            # display the image inside the panel
            self.ShowBitmap()
            # enable the 'Mirror' menu item, it only makes sense to enable it when we've loaded
            # an image as before there would be no image to mirror
            self.mirrorMenuItem.Enable(True)
            wx.EndBusyCursor()
                        
        dlg.Destroy() # we don't need the dialog any more so we ask it to clean-up

    def ShowBitmap(self):
        if self.bitmap is not None:
            self.bitmap.Destroy()
        
        # Convert to Bitmap for wxPython to draw it to screen
        self.bitmap = wx.StaticBitmap(self.panel, -1, wx.BitmapFromImage(self.image))       
        # Make the application's window as large as the image
        self.SetClientSize(self.bitmap.GetSize())
        self.Center() # open in the centre of the screen
        
    def OnExit(self, event):
        "Close the application by Destroying the object"
        self.Destroy() 
        
    
class App(wx.App):
    
    def OnInit(self):
        self.frame = Frame(parent=None, id=-1, title='Image Viewer')
        self.frame.Show()
        self.SetTopWindow(self.frame)
        return True
    
if __name__ == "__main__":       
    # make an App object, set stdout to the console so we can see errors
    app = App(redirect=False)
        
    app.MainLoop()

Got any questions?

Get answers in the ShowMeDo Learners Google Group.

Video statistics:

  • Video's rank shown in the most popular listing
  • Video plays: 79 (since July 30th)
  • Plays in last week: 0
  • Published: 79 months ago

Thank-yous, questions and comments

If this video tutorial was helpful please take some time to say thank-you to the authors for their hard work. Feel free to ask questions. Let the author know why their video tutorial was useful - what are you learning about? Did the video tutorial save you time? Would you like to see more?

You may also want to see our ShowMeDo Google Group to speak to our active users and authors.

Your email address will not be published.

Show some quick comments >>








All comments excluding tick-boxed quick-comments

Just right.

Thanks,

Mark


You certainly got my attention with the "big exercise". I found it rather amusing.


I thought the exercise was fine/solvable and the links to the wxPython documentation was clue enough. I've liked the videos so far.

I do think it's a shame that the previous versions of the code contains the commented "Mirror image" menu item. It would add to the exercise if the user should copy/paste the "Open Image" item and so on...

On Debian Linux (Python 2.5.4/ wx 2.6.3) refreshing the mirrored image isn't a problem.


The instructions were clear enough for me to do this without help.

However, I did not need to use self.Refresh().

However #2, I wonder why you have put self.Refresh() into OnMirrorImage() and not ShowBitmap(), as it's obviously ShowBitmap() that is functioning incorrectly?


I am enjoying the series but as a newbie I found the exercise too challenging at first so I had to watch the beginning of this video to be able to solve it. I got confused with 'self' and kept getting errors saying the frame not being able to mirror. As soon as I saw "self.image = self.image.Mirror()" on this video I was able to stop and solve the exercise.


I did have some successes with this which are worth mentioning. I did figure out how to set up the OnMirrorImage function straight away; but couldn't find the right lines of code to make the image actually mirror until after watching this episode. I also figured out how to mirror the image vertically; using boolean logic if Mirror( horizontal=True), then Mirror(False) will mirror the image vertically :-)

As in: ( self.image = self.image.Mirror(False) )


Review of Worked Solution - adding a Mirror function to the Image Viewer

This was a good exercise and I had fun doing

it.

I did attempt to solve the problem myself; however, I couldn't find the documentation for the solution on the wxpython.org/ wxwidgets.org websites or any other site. I do not know if I was looking in the wrong place or there is a lack of this kind of documentation.

In fact, looking at the documentation at wxpython.org is totally confusing.

Which did not suprise me, as most free documentation on websites is typically much more difficult to interpret than a textbook.

I did find the book "WxPython in Action" on the wxpython.org website. That looks to be a very good reference manual, I'll have to get that one.

Perhaps that would make a good ShowMeDo video; on how to use the wxpython.org documentation to solve these types of problems or whether there is a better source elsewhere on the net?

On a side note; I find sample code to be a good reference when solving problems such as this.WxPython comes with a great deal of different sample source projects, which helps.

So I did have to cheat and watch the next video for the answer. Searching the web, trying to find documentation to get your code to work reminds me of how much time ShowMeDo saves me :-)


I'm running under Ubuntu 8.04, Gnome. When I comment out:

#self.Refresh()

I don't see any redraw problem. When I mirror the picture looks the same. This might be a linux thing. Great video. Keep it up!


Video published, thanks for contributing to ShowMeDo


Showmedo is a peer-produced video-tutorials and screencasts site for free and open-source software (FOSS)- with the exception of some club videos, the large majority are free to watch and download.

how to help » about » faq »

Educating the Open-source Community With Showmedo

Although as important as the software it supports, education and documentation are relatively neglected in the Open-source world. Coders love to code, and explaining how best to use or improve the software tends to be deferred or even sidelined.

At Showmedo we believe the community can play a vital role here and also say thanks for the tools and software that make our lives easier. If you have a piece of software you love or a programming langugage you are enthusiastic about, why not make a screencast showing others how to use it? All the stuff you wish you'd been told, the tips, tricks, insights that would have saved you time and frustration.

Screencasting is easier than you think, and we're happy to help you. You can emailus for advice or just use some of the how-to screencasts on the site. This screencasting learning-pathis a good place to start.

Kudos and Thanks for Ian

Content

Feedback

Showmedo's development is fairly rapid and bugs will inevitably creep in. If you have any problems please drop us a line using the contact address below. Likewise, any suggestions for improvements to the site are gratefully received.

feedback@showmedo.com