LAC 2009 - Paper: The Guido Engine: A toolbox for music scores rendering

2009·0.32 MB·English

by  Christophe Daudin

The Guido Engine
A toolbox for music scores rendering
C. Daudin, D. Fober, S. Letz and Y. Orlarey
Grame
Centre national de cration musicale
Lyon, France
{daudin, fober, letz, orlarey}@grame.fr
Abstract music notation. Since MusiXTEX is powerful
but hard to learn, preprocessors such as PMX
TheGuidoMusicNotationformat(GMN)isagen-
and M-Tx have been designed to facilitate mu-
eral purpose formal language for representing score
sic input and layout. A more recent initiative is
levelmusicinaplatformindependentplaintextand
Lilypond [10], an open source software partially
human readable way. Based on this music repre-
implemented in the language Scheme, its input
sentation format, the GuidoLib provides a generic,
music representation format is simple and intu-
portable library and API for the graphical render-
itive, it includes automatic layout capabilities.
ing of musical scores. This paper gives an intro-
Both systems produce PostScript, EPS or PDF
duction to the music notation format and to the
files.
Guido graphic score rendering engine. An exam-
pleofapplication,theGuidoSceneComposer,isnext Based the Guido Music Notation format,
presented. the GuidoLib project is a open source, cross-
platform C/C++ library that provides score
Keywords layoutandrenderingcapabilitiestoitsclientap-
plications. The music notation format is very
Guido, Music notation, score layout.
close to the Lylipond format. The GuidoLib
mainly differs from the compilers approach in
1 Introduction
that it allows to embed music score rendering
Computer music has started to investigate mu- capabilities into standalone applications and to
sic score rendering very early [1][2][3]. Music create scores dynamically.
notation codes such as DARMS [4], SCORE [5]
This paper introduces first the Guido Mu-
or MuseData [6] have been designed to address
sic Notation format, next the Guido Engine
representational issues and gave birth to asso-
and the Guido library API are presented. The
ciated programs (such as the SCORE Notation
last section presents the Qt support for Guido,
Program, widely used in engraving during the
alongwithaconcreteexampleof Guido-Qtap-
1980s and 1990s) and a long history of derived
plication, the GuidoSceneComposer.
or alternate formats.
Now, commercial music publishing software
exist for more a decade and actually provide so- 2 The Guido Music Notation format
phisticated but complex solutions for music en-
graving. Along these closed solutions, the tool- The Guido Music Notation format (GMN) [11]
box approach has been investigated very early [12]hasbeendesignedbyH.HoosandK.Hamel
[7]. However, very few systems have reached more than ten years ago. It is a general pur-
maturity: the Common Music Notation system poseformallanguageforrepresentingscorelevel
[8] could be considered as the best achievement. music in a platform independent plain text and
More recently, the Expressive Notation Pack- human readable way. It is based on a concep-
age (ENP)[9]introducedanotherpromisingap- tually simple but powerful formalism: its de-
proach; both systems are Lisp based environ- sign concentrates on general musical concepts
ments. (as opposed to graphical features). A key fea-
Another solution consists in designing com- ture of the Guido design is adequacy which
pilers for producing music sheets from a tex- means that simple musical concepts should be
tual music description. MusiXTEX is among represented in a simple way and only complex
these tools: it is a set of TEX macros to typeset notions should require complex representations.
2.1 Basic concepts {
BasicGuidonotationcoverstherepresentation [\staff<1> \stemsUp \meter<"2/4">
of notes, rests, accidentals, single and multi- \beam(g2/32 e/16 c*3/32) c/8
\beam(a1/16 c2 f)
voiced music and the most common concepts
\beam(g/32 d/16 h1*3/32) d2/8
from conventional music notation such as clefs,
\beam(h1/16 d2 g)],
meter,key,slurs,ties,beaming,stemdirections,
etc. Notes are specified by their name (a b c [\staff<1>\stemsDown g1/8 e
d e f g h), optional accidentals (’#’ and ’&’ \beam(g/16 d f a) a/8 e \beam(a/16 e g h)],
for sharp and flat), an optional octave number
[\staff<2> \stemsUp \meter<"2/4"> a0 f h c1],
and an optional duration.
[\staff<2>\stemsDown f0 d g a]
Duration is specified in one of the forms:
}
’*’enum’/’denom dotting
’*’enum dotting The corresponding Guido engine output is
’/’denom dotting
given by figure 2.
where enum and denom are positive integers
and dotting is either empty, ’.’, or ’..’, with the
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Chords are described using comma separated
Figure 2: A multi-voices example
notes enclosed in brackets e.g {c, e, g}
2.2 Guido tags Additionally, the advanced Guido specifica-
Tags are used to represent additional musical tion (not covered by this paper) provides exact
information, such as slurs, clefs, keys, etc. A
formatting of the score.
basic tag has one of the forms:
\tagname 3 The Guido Engine
\tagname<param-list>
where param-list is a list of string or numer- Based on the Guido Music Notation format
ical arguments, separated by commas (’,’). In and initially designed by Kai Renz, the Guido
addition, a tag may have a time range and be
Engine provides graphical rendering of musical
applied to a series of notes (like slurs, ties etc.);
scores, including automatic layout capabilities.
the corresponding form is:
At Grame’s initiative, the engine has been re-
\tagname(note-series)
shapedundertheformofaportablelibraryand
\tagname<param-list>(note-series)
became an open source project in 2002, cov-
The following GMN code illustrates the con-
cision of the notation; figure 1 represents the ered by the GNU LGPL license and hosted on
corresponding Guido engine output. SourceForge. Since 2002, the Guido engine has
[ \meter<"4/4"> \key<-2> c d e& f/8 g ] been maintained and extended by Grame.
The Guido Engine operates on a memory
representation of the GMN format: the Guido
& bb 44 _XÛxxxxxx XÛxxxxxx XÛxxxxxx XÛxxxxxx XÛxxxxxx \ AtabtisotnracistRtreapnrsefsoernmtaedtiosnte(pGAbyR)s.teTphitsorepprroedsuence-
graphical score pages. Two kinds of processing
Figure 1: A simple GMN example
are first applied to the GAR:
2.3 Notes sequences and segments • GARtoGARtransformationswhichrepre-
A note sequence is of the form [tagged-notes] sents a logical layout transformation: part
where tagged-notes is a series of notes, tags, ofthelayout(suchasbeamingforexample)
and tagged ranges separated by spaces. Note
may be computed from the GAR as well as
sequences represent single-voiced scores. Note
expressed in GAR,
segmentsrepresentmulti-voicedscores;theyare
denoted by {seq-list} where seq-list is a
• theGARisconvertedintoaGuidoSeman-
list of note sequences separated by commas as
tic Normal Form (GSNF). The GSNF is a
shown by the example below:
canonical form such that different semanti- 4.2 Score pages access
cally equivalent expressions have the same
The result of the score layout is a set of pages
GSNF.
which size may be dynamically changed accord-
ing to an application or a user needs. The
This GSNF is finally converted into a Guido
library provides the necessary to change the
Graphic Representation (GGR) that contains
page size, to query a score pages count, or the
the necessary layout information and is directly
page number corresponding to a given music
used to draw the music score. This final step
date. Note that only one page is drawn by the
notably includes spacing and page breaking al-
GuidoOnDraw function.
gorithms [13].
Note that although the GMN format allows 4.3 Engine settings
for acurate music formatting using advanced Score layout algorithms are controlled by a set
Guido (see figure 3), the Guido Engine pro- of parameters which are global to the Guido
vides powerful automatic layout capabilities. engine. The library provides an API to query
and modify these parameters. It includes op-
4 The Guido Library timal page fill control, springs and space force
control, systems distance and systems distribu-
The Guido Library is implemented is in C++
tion.
but the services of Guido Engine are available
using a C API. 4.4 The Guido Factory
The Guido Engine may be feeded with com-
4.1 Score layout
puter generated music using the Guido Fac-
The library provides functions to parse a GMN tory. The Guido Factory API provides a set of
file and to create the corresponding GAR and
functions to create a GAR from scratch and to
GGR. GAR and GGR are referenced by opaque convert it into a GGR. The Guido Factory is a
handles which are used as arguments of any
state machine that operates on implicit current
function that operates on a score. For exam-
elements: for example, once you open a voice
ple: GuidoParse (const char * filename) pro- (GuidoFactoryOpenVoice()), it becomes the cur-
videsconversionofaGMNfileintoaGGRhan-
rent voice and all subsequent created events are
dle returned as the function result. This handle
implicitly added to this current voice.
may be next used to draw the score using the TheGuidoFactorystateincludesthecurrent
GuidoOnDraw function. score,voice,chord,note(orrest)andtag. Some
A typical code to draw a score from its GMN
elements of the factory state reflects the Guido
description is given below (see section 4.6 for
formal specification; unless otherwise specified,
VGDevice information):
new notes will implicitly carry the current du-
void DrawGMNFile (char* filename, VGDevice* device) ration and octave.
{ A music score dynamic construction is very
// data structure for engine initialization close to the textual Guido description: the
// uses fonts "guido2" and "times"
GuidoInitDesc gd = { device, 0, "guido2", "times" }; Factory API handles GAR objects that have a
// Initialise the Guido Engine first one to one relationship with the notation for-
GuidoInit (&gd);
mat. Oncethescorehasbeendynamicallybuilt,
// declare a data structure for drawing a call to GuidoFactoryCloseMusic() returns a
GuidoOnDrawDesc desc; Guido handle to a GAR, directly usable with
// and parse the GMN file to get a GGR handle GuidoFactoryMakeGR(), which returns a Guido
// directly stored in the drawing struct
desc.handle = GuidoParse (filename); handle to a GGR, directly usable with the main
services of the library. Logical layout is per-
// next setup the drawing parameters
formed before returning the GAR handle and
// (see the documentation for more details)
desc.hdc = device; // the output device graphical layout is performed before returning
desc.page = 1; // the page to draw the GGR handle.
desc.updateRegion.erase = true;
desc.scrollx = desc.scrolly = 0; 4.5 Graphic Mappings
desc.zoom = 1; // no zoom
desc.sizex = desc.sizey = 0; Along with the GGR, the Guido Engine main-
tains a tree of graphical elements for each page
// and finally draws the score
of the score, as illustrated by figure 4. Each ele-
GuidoOnDraw (&desc);
} ment has a bounding box and a date. Positions
FUGA I
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Figure 3: A complex layout example
of the elements are stored as pixel coordinates. (Windows), Quartz (Mac OS X), GTK (GNU
Top left corner of the score is at position (0, 0). Linux), OpenGL and more recently for Qt.
= 120
5 Guido Qt support
X!ÛÛÛÛÛ = 120 = 120
& 44 _X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ E!ÛÛÛÛÛÛ ‹_X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ E!ÛÛÛÛÛÛ ‹ X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ XX!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ ‹ X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ E!ÛÛÛÛÛÛ ‹ Qt is a cross-platform application development
framework[14],widelyusedforthedevelopment
of GUI programs1.
& _X!ÛÛÛÛÛÛ _X!ÛÛÛÛÛÛ E!ÛÛÛÛÛÛ ‹_X!ÛÛÛÛÛÛ _X!ÛÛÛÛÛÛ E!ÛÛÛÛÛÛ ‹ X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ ‹ X!ÛÛÛÛÛÛ X!ÛÛÛÛÛÛ _E!ÛÛÛÛÛÛ \ 5.1 GuidoQt classes
A set of classes has been developed to use the
Guido library with Qt; they are organized in 3
Figure 4: Bounding rects of a score elements
layers (figure 5):
The Guido library provides a specific API to
• low level: GDeviceQt, GFontQt & GSys-
querythescoremapandtoretrieveelementsby
temQt: Qt implementation of the Virtual
type, position and date.
Graphic System
4.6 The Virtual Graphic System
• middle level: QGuidoPainter: a class that
The virtual graphic system is intended as an
uses GDeviceQt, GFontQt & GSystemQt,
abstract layer covering platform dependencies
and offers a higher-level interface
at graphic level. It represents a set of abstract
classes adressing the basic needs of an applica- • high level: ready-to-use Qt classes that
tion: printing text, drawing on the screen or uses the QGuidoPainter to parse and draw
offscreen, etc. The set of abstract classes in- Guido scores:
cludes:
– QGuidoWidget, a QWidget
• a VGDevice class: specialized on drawing
– QGuidoSPageItem & QGuidoM-
onscreen or offscreen
PageItem, two QGraphicsItem
• a VGFont class: to cover fonts management displaying, respectively, one score’s
page at a time, and all the pages
• a VGSystem class: to cover allocation of
specific VGDevice and VGFont objects. – Guido2Image, to export Guido scores
to various image formats
This set of classes is implemented for different
target platforms: support is provided for GDI 1see: http://www.qtsoftware.com
(c) Kai Renz, musical data taken from MuseData database and automatically converted to GUIDO
Qt Library QGraphicsItem QWidget
High level QGuidoMPageItem QGuidoSPageItem QGuidoWidget Guido2Image
QGuidoItem
Mid level QGuidoPainter
Low level GSystemQt GDeviceQt GFontQt
Figure 5: GuidoQt class diagram
Here is a short example using the #include <QApplication>
QGuidoPainter that shows how to export #include "QGuidoWidget.h"
a Guido score to an image: #include "QGuidoPainter.h"
int main(int argc, char *argv[])
#include <QApplication> {
#include <QPainter> QApplication app(argc, argv);
#include <QImage>
#include "QGuidoPainter.h" // Guido Engine initialization
int main(int argc , char* argv[]) QGuidoPainter::startGuidoEngine();
{
QApplication app( argc , argv ); // Create a QGuidoWidget...
QGuidoWidget w;
//Guido Engine initialization //...and give it some Guido Music Notation
QGuidoPainter::startGuidoEngine(); w.setGMNCode( "[e d c]" );
w.show();
//Create a QGuidoPainter...
QGuidoPainter* p = QGuidoPainter::create(); // That’s it !
//...and give it some Guido Music Notation int result = app.exec();
p->setGMNCode( "[c/8 d e g e d c]" );
// Destroy the Guido Engine resources
//Get the size of the score’s first and only page QGuidoPainter::stopGuidoEngine();
int pageIndex = 1; return result;
QSizeF s = p->pageSizeMM( pageIndex ); }
5.2 The Guido Scene Composer
//Create a blank image, using the size of the score
QImage image(s.toSize()*10 , QImage::Format_ARGB32); The GuidoSceneComposer is a graphic IDE for
image.fill( QColor(Qt::white).rgb() );
Guido,allowingtomanipulateGuidoscoresin
//Draw the score with the QGuidoPainter, via QPainter.a graphic scene.
QPainter painter( &image );
5.2.1 A Guido Music Notation learning
p->draw( &painter , pageIndex , image.rect() );
tool
QGuidoPainter::destroyGuidoPainter( p );
The GuidoSceneComposer is an effective envi-
//Destroy the Guido Engine resources ronment to learn the GMN:
QGuidoPainter::stopGuidoEngine();
• whentypingGMN,thecorrespondingscore
image.save( "myScore.png" ); is instantly updated, making it very simple
return 0;
to try different notations;
}
And here is another example showing how to • a help palette (figure 6) lists a large as-
display a Guido Score using a QGuidoWidget: sortment of Guido expressions and tags,
so that no external documentation is nec- 6 Conclusions
essary; Based on the Guido Music Notation for-
• the GMN text editor uses a synthax high- mat, the GuidoLib is a unique open source,
lighter, for a clearer GMN reading; platform-independant library, for embedding
score rendering into a standalone application.
• import MusicXML and MuseData (limited The recent support of the widely-used cross-
support) scores; platform Qt library makes it even more accessi-
• export the Guido scores to a pdf or an im- ble to software developers.
Inthefuture, weplantoextendthegraphical
age.
possibilities of the GuidoSceneComposer giv-
ing to users more drawing tools; it would then
become an interesting application to create ex-
tended modern music scores. Support of im-
port/export in other common music score for-
mats is also among our concerns.
Finally,weplantoaddscorecompositionfea-
tures, like putting scores in sequence or in par-
allel, cutting the head, the tail, the top or the
bottom voices of a score, transposition, or du-
ration change, using an homogeneous approach,
where scores are both the target and the argu-
ment of the operations.
Figure 6: The Guido Help palette
TheGuidolibraryisavailableonSourceforge
at http://guidolib.sourceforge.net
5.2.2 A score graphic composer
The GuidoSceneComposer allows to you to References
compose graphic scenes with different scores:
[1] David A. Gomberg. A Computer-Oriented
System for Music Printing. In Computers
• move, resize, copy & paste the scores, to
and the Humanities, volume 11, pages 63–
createagraphicallycomplexmusicalscene,
80. Pergamon Press, 1977.
• importvariousformatsofpicturestoenrich
[2] Donald Alvin Bird. Music Notation by
the scene,
Computer. PhD thesis, Indiana University,
• add textual annotations, 1984.
• export the scene to an image or a pdf. [3] John S. Gourlay, A. Parrish, D. Roush,
F. Sola, and Y. Tien. Computer For-
matting of Music. Technical report OSU-
CISRC-2/87-TR3, Department of Com-
puter and Information Science, The Ohio
State University, 1987.
[4] E. Selfridge-Field. DARMS, Its Dialiects,
and Its Uses. In Beyond MIDI, The hand-
book of Musical Codes., pages 163–174.
MIT Press, 1997.
[5] Smith Leland. SCORE. In Beyond MIDI,
The handbook of Musical Codes., pages
252–280. MIT Press, 1997.
[6] Walter B. Hewlett. MuseData: Multipur-
pose Representation. In Selfridge-Field E.,
editor,BeyondMIDI,ThehandbookofMu-
Figure 7: The Guido Scene Composer sical Codes., pages 402–447. MIT Press,
1997.
[7] Assayag G. and D. Timis. A ToolBox for
Music Notation. In Proceedings of the In-
ternational Computer Music Conference,
pages 173–178, 1986.
[8] Bill Schottstaedt. Common Music Nota-
tion. In Selfridge-Field E., editor, Beyond
MIDI, The handbook of Musical Codes.,
pages 217–222. MIT Press, 1997.
[9] Mika Kuuskankare and Michael Laurson.
ENP - Music Notation Library based on
Common Lisp and CLOS. In Proceedings
of the International Computer Music Con-
ference, pages 131–134. ICMA, 2001.
[10] Han-Wen Nienhuys and Jan Nieuwen-
huizen. LilyPond, a system for automated
musicengraving. InProceedings of the XIV
Colloquium on Musical Informatics (XIV
CIM 2003), May 2003.
[11] HoosH., HamelK.A., RenzK., andKilian
J. The GUIDO Music Notation Format - a
Novel Approach for Adequately Represent-
ingScore-levelMusic. InProceedings of the
International Computer Music Conference,
pages 451–454. ICMA, 1998.
[12] H. H. Hoos and K. A. Hamel. The GUIDO
Music Notation Format Specification - ver-
sion 1.0, part 1: Basic GUIDO. Techni-
calreportTI20/97,TechnischeUniversitat
Darmstadt, 1997.
[13] Kai Renz. Algorithms and Data Struc-
tures for a Music Notation System based
on GUIDO Music Notation. PhD thesis,
Technischen Universit¨at Darmstadt, 2002.
[14] Jasmin Blanchette and Mark Summerfield.
C++ GUI Programming with Qt 4 (2nd
Edition). Prentice Hall, 2008.