Book Image

Python 2.6 Graphics Cookbook

By : Michael J Ohlson
Book Image

Python 2.6 Graphics Cookbook

By: Michael J Ohlson

Overview of this book

Python is a great object-oriented and interactive programming language that lets you develop graphics, both static and animated, using built-in vector graphics functions that are provided with Python. Python 2.6 Graphics Cookbook is a collection of straightforward recipes and illustrative screenshots for creating and animating graphic objects using the Python language. This book makes the process of developing graphics interesting and entertaining by working in a graphic workspace without the burden of mastering complicated language definitions and opaque examples. If you choose to work through all the recipes from the beginning, you will learn to install Python and create basic programs for making lines and shapes using the built-in Tkinter module. The confusing topic of color manipulation is explored in detail using existing Python tools as well as some new tools in the recipes. Next you will learn to manipulate font size, color, and placement of text as placing text exactly where you want on a screen can be tricky because font height, inter-character spacing, and text window dimensions all interfere with each other. Then you will learn how to animate graphics, for example having more than one independent graphic object co-exist and interact using various Python methods. You will also learn how you can work with raster images, such as converting their formats using the Python Imaging Library. Next you will learn how you can combine vector images with raster images so that you can animate the raster images with ease. You will also walk through a set of recipes with the help of which you can handle and manipulate blocks of raw data that may be hundreds of megabytes in size using datastreams, files, and hard drives. You will also learn how you can use Inkscape to dismantle existing images and use parts of them for your own graphics and Python programs. At the end of the book you will learn how you can create GUIs for different purposes.

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Python 2.6 Graphics Cookbook
Michael J Ohlson
Nov, 2010 | 260 pages
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Table of Contents (18 chapters)
Python 2.6 Graphics Cookbook
Python 2.6 Graphics Cookbook
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
Preface
Preface
Free Chapter
1
Start your Engines
Start your Engines
Introduction
Running a shortest Python program
Ensuring that the Python modules are present
A basic Tkinter program
Make a compiled executable under Windows and Linux
2
Drawing Fundamental Shapes
Drawing Fundamental Shapes
Introduction
A straight line and the coordinate system
Draw a dashed line
Lines of varying styles with arrows and endcaps
A two segment line with a sharp bend
A line with a curved bend
Drawing intricate shapes – the curly vine
Draw a rectangle
Draw overlapping rectangles
Draw concentric squares
A circle from an oval
A circle from an arc
Three arc ellipses
Polygons
A star polygon
Cloning and resizing stars
3
Handling Text
Handling Text
Introduction
Simple text
Text font type, size, and color
Alignment of text – left and right justify
All the fonts available on your computer
4
Animation Principles
Animation Principles
Introduction
Static shifting of a ball
Time-controlled shifting of a ball
Complete animation using draw-move-pause-erase cycles
More than one moving object
A ball that bounces
Bouncing in a gravity field
Precise collisions using floating point numbers
Trajectory tracing and ball-to-ball collisions
Rotating line
Trajectory tracing on multiple line rotations
A rose for you
5
The Magic of Color
The Magic of Color
Introduction
A limited palette of named colors
Nine ways of specifying color
A red beachball of varying hue
A red color wedge of graded hue
Newton's grand wheel of color mixing
The numerical color mixing matching palette
The animated graded color wheel
Tkinter's own color picker-mixer
6
Working with Pictures
Working with Pictures
Opening an image file and discovering its attributes
Open, view, and save an image in a different file format
Image format conversion for JPEG, PNG, TIFF, GIF, BMP
Image rotation in the plane of the image
Image size alteration
Correct proportion image resizing
Separating one color band in an image
Red, green, and blue color alteration in images
Slider controlled color manipulation
Combining images by blending
Blending images by varying percentages
Make a composite image using a mask image
Offset (roll) image horizontally and vertically
Flip horizontally, vertically, and rotate
Filter effects: blur, sharpen, contrast, and so on
7
Combining Raster and Vector Pictures
Combining Raster and Vector Pictures
Simple animation of a GIF beach ball
The vector walking creature
Bird with shoes walking in the Karroo
Making GIF images with transparent backgrounds using GIMP
Diplomat walking at the palace
Spider in the forest
Moving band of images
Continuous band of images
Endless background
8
Data In and Data Out
Data In and Data Out
Introduction
Creation of a new file on a hard drive
Writing data to a newly-created file
Writing data to multiple files
Adding data to existing files
Saving a Tkinter-drawing shape to disk
Retrieving Python data from disk storage
Simple mouse input
Storing and retrieving a mouse-drawn shape
A mouse-line editor
All possible mouse actions
9
Exchanging Inkscape SVG Drawings with Tkinter Shapes
Exchanging Inkscape SVG Drawings with Tkinter Shapes
Introduction
The structure of an SVG drawing
Tracing the shape of an image in Inkscape
Converting an SVG path into a Tkinter Line
10
GUI Construction: Part 1
GUI Construction: Part 1
Introduction
Widget configuration – a label
Button focus
The simplest push button with validation
A data entry box
Colored button causing a message pop-up
Complex interaction between buttons
Images on buttons and button packing
Grid Geometry Manager and button arrays
Drop-down menus to select from a list
Listbox variable selection
Text in a window
11
GUI Construction: Part 2
GUI Construction: Part 2
Introduction
The Grid Layout Geometry Manager
The Pack Geometry Manager
Radiobuttons to select one from many
Checkbuttons (Tickboxes) to select some of many
Key-stroke event handling
Scrollbar
Custom DIY controller widgets
Organizing widgets inside frames
Quick tips for running Python programs in Microsoft Windows
Quick tips for running Python programs in Microsoft Windows
Running Python programs in Microsoft Windows
Where will we find the windows installer?
Do we have to use Python version 2.7?
Why do we get "python is not recognized…"?
Index
Index

Running a shortest Python program

We need a one line Python program that will prove that the Python interpreter is installed and working on our computer platform.

How to do it...

  1. Create a folder (directory) called something like construction_work or constr for short. You will place all your Python programs inside this directory. In a text editor such as gedit on Linux or notepad on Windows. If we are working in Windows, there is a nice editor called "Context" that can be downloaded for free from http://www.contexteditor.org/ Context, that is sensitive to Python syntax and has a search-and-replace function that is useful.

  2. Type the following line:

    Print 'My wereld is "my world" in Dutch'

  3. Save this as a file named simple_1.py, inside the directory called constr.

  4. Open up an X terminal or a DOS window if you are using MS Windows.

  5. Change directory into constr - where simple_1.py is located.

  6. Type python simple_1.py and your program will execute. The result should look like the following screenshot:

  7. This proves that your Python interpreter works, your editor works, and that you understand all that is needed to run all the programs in this book. Congratulations.

    """
Program name: simplest_1.py
Objective: Print text to the screen.

Keywords: text, simplest
=========================
Printed "mywereld" on terminal.
Author:          Mike Ohlson de Fine

"""
Print 'mywereld is "my world" in Dutch'

How it works...

Any instructions you type into a Linux X terminal or DOS terminal in MS Windows are treated as operating system commands. By starting these commands from within the same directory where your Python program is stored you do not have to tell the Python and operating system where to search for your code. You could store the code in another directory but you would then need to precede the program name with the path.

There's more...

Try the longer version of the same basic print instructions shown in the following program.

All the text between the """ (triple quotation marks) is purely for the sake of good documentation and record keeping. It is for the use of programmers, and that includes you. Alas, the human memory is imperfect. Bitter experience will persuade you that it is wise to provide fairly complete information as a header in your programs as well as comments inside the program.

However, in the interest of saving space and avoiding distractions, these header comments have been left out in the rest of this book.

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