The Tiles Teachpack

This teachpack provides a variety of functions for manipulating graphical images. To use it, you'll need to

download it to your computer,
install it in the right place in your computer, and
load it in DrScheme.

To download and install

This should be done once on your home computer, and you'll never have to do it again (unless I come up with an improved version). If you do it on a classroom computer, the teachpack may be uninstalled before the next time you come to class, so you'll have to do it again (unless I can persuade the Computing Center to install it permanently).

The easy way

Start DrScheme, go to the "File" menu, choose "Install .plt file...", make sure you're in the "Web" tab rather than the "File" tab, type the URL "http://www.adelphi.edu/sbloch/class/160/tiles.plt" into the blank, and hit "OK". It should be downloaded and installed.

However, on some computers this doesn't seem to work: you get messages like "gnu-unzip: bad header" and "not an unpackable distribution archive". If that happens, try...

The second easiest way

Right-click on the link tiles.plt, choose "Save file as...", and save it somewhere on your computer. Wherever you put it, it should appear with a red-white-and-blue DrScheme logo. If so, double-click on it and it should install automatically (perhaps showing a black window for a few seconds).

If the file appears with some other kind of logo, try...

The third easiest way

Once you've saved the tiles.plt file somewhere on your computer, start DrScheme, choose "File->Install .plt file...", click the "File" tab, then the "Browse" button, navigate to wherever you put the file, select it, and hit "OK". You should get a bunch of messages ending with "Done setting up."

If that doesn't work, talk to me.

To load in DrScheme

When you start DrScheme, you can tell it you want to use these added functions, and it'll remember that for the next time you start DrScheme on the same computer... unless somebody else using the same computer tells it not to use this teachpack, in which case you'll need to go through these steps again.

Go to the "Language" menu in DrScheme and choose "Add Teachpack", select "tiles.ss", click "Open", and then click the "Run" button. You should see a message saying "Teachpack: ... tiles.ss" in the interactions window. The next time you start DrScheme, it should remember this unless you choose "Language->Clear Teachpack" to remove the teachpack.

What does it do?

You can copy-and-paste images from a Web browser into DrScheme and use them just like any other value: you can store them in a variable, etc. This teachpack includes several useful functions for manipulating images:

```
image-above: image image -> image
```
Combines two images into one, putting the first on top of the second.
```
image-beside: image image -> image
```
Combines two images into one, putting the first to the left of the second.
```
reflect-vert : image -> image
```
flips an image top-to-bottom.
```
reflect-horiz : image -> image
```
flips an image left-to-right.
```
reflect-main-diag : image -> image
```
flips an image top-left to bottom-right.
```
reflect-other-diag : image -> image
```
flips an image top-right to bottom-left.
```
rotate-cw : image -> image
```
rotates an image 90 degrees clockwise.
```
rotate-ccw : image -> image
```
rotates an image 90 degrees counter-clockwise.
```
rotate-180 : image -> image
```
rotates an image 180 degrees.
```
overlay : image image image ... -> image
```
piles the images on top of one another, with the first covered by the second, the second covered by the third, etc. Presumably you would only do this if the second were smaller than the first, so you could still see the first image around the edges of the second.

It also includes a number of useful functions for creating images from scratch:

```
rectangle: number number mode color -> image
```
where mode is either "outline" or "solid" (in quotation marks), and color is the name of a color ("red", "yellow", "white", "black", "blue", "green", etc. in quotation marks). The first number is the width of the rectangle, and the second number is the height.
```
circle: number mode color -> image
```
The number is the radius of the circle.
```
ellipse: number number mode color -> image
```
The two numbers are the width and height, respectively, of the ellipse.
```
triangle: number mode color -> image
```
Produces an equilateral triangle, each side of which is specified by the number.
```
line: number (x) number (y) color -> image
```
Produces a colored line from (0,0) to the specified coordinates. Note that both numbers must be positive; larger x is to the right, and larger y is down on the screen.
```
text: string number color -> image
```
Draws the specified string in the specified point size and color. (No font control at this point; this is a simple image library!)

It also includes functions to find out information about an image:

```
image-inside?: image image -> boolean
```
tells whether the second image appears as part of the first
```
image-width : image -> number
```
tells how many pixels wide the image is
```
image-height : image -> number
```
tells how many pixels high the image is

There are numerous other, more obscure, functions provided; to learn about them, start DrScheme, choose "Help -> Help Desk", and search for "image.ss" (my "tiles.ss" teachpack is an enhancement of the built-in "image.ss", including all the same functions and a few improvements).

Last modified:

Stephen Bloch / sbloch@adelphi.edu