Book Image

Tcl/Tk 8.5 Programming Cookbook

Book Image

Tcl/Tk 8.5 Programming Cookbook

Overview of this book

With Tcl/Tk, you can create full-featured cross-platform applications in a simple and easy-to-understand way without any expensive development package; the only tools required are a simple text editor and your imagination. This practical cookbook will help you to efficiently interact with editors, debuggers, and shell type interactive programs using Tcl/Tk 8. This cookbook will comprehensively guide you through practical implementation of Tcl/Tk 8.5 commands and tools. This book will take you through all the steps needed to become a productive programmer in Tcl/Tk 8. Right from guiding you through the basics to creating a stand-alone application, it provides complete explanation of all the steps along with handy tips and tricks. The book begins with an introduction to the Tcl shell, syntax, variables, and programming best practices in the language. It then explores procedures and the flow of events with control constructs followed by advanced error trapping and recovery. From Chapter 4, a detailed study of string expressions and handling enables you to handle various string functions and use lists to expand the string functionality. The book then discusses in-depth the Tcl Dictionary and how to utilize it to store and retrieve data. File operations and Tk GUI handling are covered extensively along with a developing a real-world address book application to practice the concepts learned.
Table of Contents (20 chapters)
Tcl/Tk 8.5 Programming Cookbook
Credits
About the Author
Acknowledgment
About the Reviewers
www.PacktPub.com
Preface

Creating an image


Before you can display a graphic in Tk, you must first create a Tk image. To accomplish this, Tk provides the image command. This command allows you to create, delete, and query the keywords for any of the supported image types. The built-in image types are bitmap (two color graphics) and photo. The photo types as shipped in the base distribution are PPM/PGM and GIF.

Based on the keyword used the image command takes several syntactic forms. The syntax and keywords are as follows:

image keyword path

Keyword

Interpretation

create

Creates an image and a command with the same name.

delete

Deletes the named image.

height

Returns a decimal string containing the height of the image in pixels.

inuse

Returns a Boolean value indicating if the named image provided is currently in use.

names

Returns a list containing the names of all created images.

type

Returns the type of image as referenced by name.

types

Returns a lost containing all valid image types...