Using Squeak for
media computation
Graphics and sound low-level
manipulations in Squeak
(Smalltalk)
What is Squeak?


Re-implementation and extension of (original) Smalltalk-80, with VM
written in Smalltalk
Runs on over 30 different platforms, including Linux, Windows,
MacOS, Solaris…even Windows CE


Apple license allows commercial apps, but system fixes must be
posted
Squeak has faster, more stable, cross-platform media than Java
Media: 3-D graphics, MIDI, Flash, MPEG, sound recording
 Network: Web, POP/SMTP, zip compression/decompress
 Beyond Smalltalk-80: Exceptions, namespaces

Squeak Books
Heart of graphics in Squeak: Form

The class Form is what represents pictures in any
Smalltalk.

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To display a Form in Smalltalk, you can just send it the
message display
To display it in a “window” (Morph) in Squeak, use a
SketchMorph


To load it from a file, Form fromFileNamed: ‘myfile.gif’ (or
.jpg or .bmp)
(SketchMorph withForm: form) openInWorld
To write it out to JPEG file, use form
writeJPEGfileNamed: filename
Manipulating pixels in Squeak

Forms understand form colorAt: x@y which
returns a Color
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Colors understand methods like red, green, blue,
lighter, darker, duller, brighter
Color will create new colors with the r:g:b: method
Forms understand form colorAt: x@y put:
aColor
Negative example in Squeak
form := Form fromFileNamed: 'C:\Documents and Settings\Mark
Guzdial\My Documents\mediasources\barbara.jpg'.
1 to: (form width) do: [:x |
1 to: (form height) do: [:y |
color := form colorAt: x@y.
newcolor := Color r: (1.0-color red) g: (1.0-color green) b: (1.0-color
blue).
"newcolor := Color r: (color luminance) g: (color luminance) b: (color
luminance)."
form colorAt: x@y put: newcolor]].
(SketchMorph withForm: form) openInWorld.
Squeak Music Essays on CD
Sound Support in Squeak

Class AbstractSound is heart of sound support in
Squeak

It knows how to write files
sound storeWAVonFileNamed: ‘fred.wav’
 sound storeAIFFonFileNamed: ‘fred.aif’

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Class SampledSound knows how to read
recorded sounds
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(SampledSound fromAIFFfileNamed: '1.aif') play
(SampledSound fromWaveFileNamed:
'c:\windows\media\chimes.wav') play
Manipulating Sounds: SoundBuffer

A SoundBuffer knows how to manipulate
samples for conversion to sounds later
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sr := SoundPlayer samplingRate.
anArray := SoundBuffer newMonoSampleCount: (sr *
seconds) .
SoundBuffers are manipulated with at:put: and
at: like any other array in Smalltalk.
You get the SoundBuffer for a SampledSound
using the method samples
Converting SoundBuffers to
SampledSounds
|base sound|
“Generate a SoundBuffer at the right frequency”
base := SoundBufferGenerator forFreq: 440 amplitude: 3000
duration: 2.
sound := SampledSound samples: base samplingRate:
SoundPlayer samplingRate.
sound viewSamples.
"sound play."
Playing a sound backwards in
Squeak
source := SampledSound fromWaveFileNamed:
'C:\Documents and Settings\Mark Guzdial\My
Documents\mediasources\thisisatest2.wav'.
target := source copy.
samples := target samples.
sourceIndex := source samples size.
1 to: (samples size) do: [:index |
samples at: index put: (source samples at: sourceIndex).
sourceIndex := sourceIndex - 1.].
target play.