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: 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: 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: 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: 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 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.