The personal website of Scott W Harden

Coder's Block

I like the idea of writing a set of tools for scientific frequency analysis (more than just turning audio into images), and I keep starting over re-coding things from scratch. I develop too much, too quickly, and half way in I get overwhelmed and mentally blocked. I do it to myself. I’ve taken about a week off and will continue to take a few more days off to reset my mind. I’m trying to improve my coding by reading books (e-books) about advanced Python programming. Perhaps when it’s time to return, I’ll write gorgeous and functional code. I always seem to have one or the other, but never both [sigh]

The photo above is the signal of my (AJ4VD) little homemade transmitter in Gainesville, Florida, USA (using a 20-ft piece of wire inside my apartment as an antenna) detected by ON5EX in Belgium. It makes me happy. It reminds me that some of the projects I work on succeed, which gives me motivation to continue pursuing the ones which currently challenge me.

Getting GTK, Glade, and Python to Work in Windows

These screenshots show me running the Py2EXE-compiled script I wrote last weekend on a Windows 7 machine. Additionally there is a screenshot of the “Add/Remove Programs” window demonstrating which versions of which libraries were required.

Python Script with GTK GUI Compiled with Py2EXE

This is a total hack, but it works. I spent all night jumping through hoops to get this thing to run on Windows. The problem is that I designed my previous UI in a version of GLADE which is newer than that supported by Windows. It looks like it’s not backward-compatible, so I have to re-design the GUI from scratch using an earlier version of GLADE. I’ll probably stick to GTK version 2.12 and Python version 2.6 because they play nicely on Windows. It’s a quick and dirty script, but I was able to make the following run on Windows as a single EXE file!

Scott from the future (10 years later): Where’s the source code for this? Weird post.

Spectrograph UI Made with Glade

While continuing to investigate my options for the new version of QRSS VD, I re-visited Glade, the GTK GUI designer. In short, it lets you draw widgets (combo boxes, scrollbars, labels, images, buttons, etc) onto windows and then makes it easy to add code to the GUI. I *hated* the old QRSS VD development because of the ridiculously large amount of time I had to spend coding the UI. Hopefully by migrating from TKinter to GTK - while it opens a whole new can of worms - will let me add functionality rapidly without hesitation.

Here’s a quick screenshot of my running this new version of the software with a GUI I made in less than an hour. The bars for brightness and contrast can be adjusted which modify the spectrograph in real time. The audio is whatever is playing in Pandora. I like the “fantastic plastic machine” radio station!

Fast TK Pixelmap generation from 2D Numpy Arrays in Python

I had TKinter all wrong! While my initial tests with PyGame’s rapid ability to render Numpy arrays in the form of pixel maps proved impressive, it was only because I was comparing it to poor TK code. I don’t know what I was doing wrong, but when I decided to give TKinter one more shot I was blown away – it’s as smooth or smoother as PyGame. Forget PyGame! I’m rendering everything in raw TK from now on. This utilizes the Python Imaging Library (PIL) so it’s EXTREMELY flexible (supports fancy operations, alpha channels, etc).

The screenshot shows me running the script (below) generating random noise and “scrolling” it horizontally (like my spectrograph software does) at a fast rate smoothly (almost 90 FPS!). Basically, it launches a window, creates a canvas widget (which I’m told is faster to update than a label and reduces flickering that’s often associated with rapid redraws because it uses double-buffering). Also, it uses threading to handle the calculations/redraws without lagging the GUI. The code speaks for itself.

import Tkinter
from PIL import Image, ImageTk
import numpy
import time

class mainWindow():
    times = 1
    timestart = time.clock()
    data = numpy.array(numpy.random.random((400, 500))*100, dtype=int)

    def __init__(self):
        self.root = Tkinter.Tk()
        self.frame = Tkinter.Frame(self.root, width=500, height=400)
        self.canvas = Tkinter.Canvas(self.frame, width=500, height=400)
        self.canvas.place(x=-2, y=-2)
        self.root.after(0, self.start)  # INCREASE THE 0 TO SLOW IT DOWN

    def start(self):
        global data
        self.im = Image.fromstring('L', (self.data.shape[1],
                                         self.data.shape[0]), self.data.astype('b').tostring())
        self.photo = ImageTk.PhotoImage(image=self.im)
        self.canvas.create_image(0, 0, image=self.photo, anchor=Tkinter.NW)
        self.times += 1
        if self.times % 33 == 0:
            print "%.02f FPS" % (self.times/(time.clock()-self.timestart))
        self.root.after(10, self.start)
        self.data = numpy.roll(self.data, -1, 1)

if __name__ == '__main__':
    x = mainWindow()