Using Squeak for media computation

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. To load it from a file, Form fromFileNamed: ‘myfile.gif’ (or .jpg

or .bmp) 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 (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 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 Squeakform := 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’

Class SampledSound knows how to read recorded sounds (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 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 Squeaksource := 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.