Vertical offset when displaying an image with wxPython

Question

Here is how we can display an image in a wxPython frame.

import wx

class Viewer(wx.App):
    def __init__(self, redirect=False, filename=None):
        wx.App.__init__(self, redirect, filename)
        self.frame = wx.Frame(None, title='Viewer')
        self.panel = wx.Panel(self.frame)
        self.imageCtrl = wx.StaticBitmap(self.panel, wx.ID_ANY, wx.BitmapFromImage(wx.EmptyImage(800,600)))
        self.mainSizer = wx.BoxSizer(wx.VERTICAL)
        self.mainSizer.Add(self.imageCtrl, 0, wx.ALL, 5)
        self.onView('0.png')
        self.panel.Layout()        
        self.frame.Show()

    def onView(self, filename):
        img = wx.Image(filename, wx.BITMAP_TYPE_ANY)
        self.imageCtrl.SetBitmap(wx.BitmapFromImage(img))
        self.panel.Refresh()
        self.mainSizer.Fit(self.frame)
        
Viewer().MainLoop()

If the test image has large dimensions, e.g. 912 x 3616 (here is the 0.png I used), I would like to set a vertical offset, i.e. the upper corner of the frame should not be (0,0) of the image but (0,500) i.e. a 500px vertical offset.

How to set a vertical offset to an image with wxPython?

Answer 1

If you really want to truncate the image, the most straightforward thing is to just do it, i.e. create a new image using wxImage::GetSubImage() with the region starting at (0, 500).

More usually, you would use a scrolled window and then you could scroll it by 500 vertically initially, but still allow the user to scroll back to the origin.

It is also possible to use scroll window without scrollbars, but this seems rather pointless.