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CSC 160
Computer Programming
for Non-Majors
Lecture #3b: Working with Pictures
Prof. Adam M. Wittenstein
A preview of today…
• So far we called pre-defined functions with
numbers, words, and sentences.
• Today, we call pre-defined functions with
images (pictures and shapes).
• Then, we will see how to define variables
in Scheme.
Data Type: Image
• Another type of data. Fun to process images.
• Images are values like numbers, booleans,
words, or sentences – they can be used inside
• Usually given names, since the same image can
be used with several different functions.
• There are predefined functions to create shapes.
Besides that, all other images (pictures) are
inserted as follows:
Inserting Images
• You cannot type in images the way you type in a
number or a word.
• To insert an image into a program, move the
blinking caret to the place in your program
where you want the image, and select the Insert
Image item from the Special menu.
• DrScheme will then provide a dialog for
selecting an image file.
• After you have selected a file, the image will be
inserted at the blinking caret.
I. Calling Functions with Images
Calling Functions involving Images
• Once you have inserted the image (usually
a picture), it is treated the same way as
any other (simple) data type.
• You can use image objects as arguments
in a function.
• Image objects can be the result of a
Install two teachpacks
Open Internet Explorer and type in the website,
Save the file to the folder
Then in DrScheme, go to “File >Install .plt File > File >
Now, as for any teachpack, choose “Language -> Add
Teachpack -> tiles (bottom one)” and click Run.
Also, add the “” teachpack. Choose “Language
-> Add Teachpack -> htdp -> world” and click Run.
Some “” functions
reflect-horiz : image -> image
reflect-vert : image -> image
image-beside : image image -> image
image-above : image image -> image
rotate-cw : image -> image
rotate-ccw : image -> image
rotate-180 : image -> image
Exercise 1: Calling Image Functions
Insert a picture into your DrScheme file either
from your computer or a website.
Find the horizontal mirror image of the picture.
Put your picture next to itself.
Put your picture next to its horizontal mirror
III. Preparing for Next Class
In summary…
• Pictures have to be inserted. They cannot
simply be typed in like numbers, words, and
sentences can.
• However, after inserting them, they are treated
like any other data type.
Next time…
• More practice with images
• Defining variables
Homework for next time…
• No written assignments.
• Readings:
– Read the article on Pair Programming.
– Read Sections 2.2-2.3 of How to Design
– Read Chapter 4 of Simply Scheme.
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