Pen | SuperCollider 3.13.0 Help

Location: NOT INSTALLED!

Description

A class which allows you to draw custom graphics on a UserView or Window.

The following methods must be called within a Window: -drawFunc or a UserView: -drawFunc function, and will only be visible once the window or the view is refreshed. Each call to Window: -refresh or UserView: -refresh will 'overwrite' all previous drawing by executing the currently defined function, unless UserView: -clearOnRefresh is set to false

Class Methods

Construct path

The following methods define paths. You will need to call *stroke or *fill to actually draw them.

.moveTo

Move the Pen to point.

Arguments:

point

An instance of Point

.lineTo

Draw a line (define a path) from the current position to point.

Arguments:

point

An instance of Point

.line

Draw a line (define a path) from p1 to p2. Current position will be p2.

Arguments:

p1	An instance of Point
p2	An instance of Point

.curveTo

Draws a cubic bezier curve from the current position to point. cpoint1 and cpoint2 are control points determining the curve's curvature.

Arguments:

endPoint	An instance of Point
cPoint1	An instance of Point
cPoint2	An instance of Point

.quadCurveTo

Draws a quad bezier curve from the current position to point. cpoint is a control point determining the curve's curvature.

Arguments:

endPoint	An instance of Point
cPoint	An instance of Point

.arcTo

Draws an arc of a circle using a radius and tangent points.

Arguments:

point1	The end point of the first tangent line. Its start point is the current position. An instance of Point
point2	The end point of the second tangent line. Its start point is point1. An instance of Point
radius	The radius of the arc.

Discussion:

example:( var w = Window("arcTo", Rect(100, 200, 300, 300)).front; var r= 15; w.drawFunc = { |v| Pen.fillColor = Color.blue; Pen.strokeColor = Color.red; Pen.moveTo(150@150); Pen.arcTo(200@150, 200@225, r); Pen.arcTo(200@225, 100@225, r); Pen.arcTo(100@225, 100@150, r); Pen.arcTo(100@150, 150@150, r); Pen.lineTo(150@150); Pen.fillStroke; }; )

.addArc

Draw an arc around the Point center, at radius number of pixels. startAngle and arcAngle refer to the starting angle and the extent of the arc, and are in radians [0..2pi].

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { Pen.translate(100, 100); 10.do{ // set the Color Pen.color = Color.red(rrand(0.0, 1), rrand(0.0, 0.5)); Pen.addArc((100.rand)@(100.rand), rrand(10, 100), 2pi.rand, pi); Pen.perform([\stroke, \fill].choose); } }; w.refresh; )

.addWedge

Draw a wedge around the Point center, at radius number of pixels. startAngle and sweepLength refer to the starting angle and the extent of the arc, and are in radians [0..2pi].

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { Pen.translate(100, 100); 10.do{ // set the Color Pen.color = Color.blue(rrand(0.0, 1), rrand(0.0, 0.5)); Pen.addWedge((100.rand)@(100.rand), rrand(10, 100), 2pi.rand, 2pi.rand); Pen.perform([\stroke, \fill].choose); } }; w.refresh; )

.addAnnularWedge

Draw an annular wedge around the Point center, from innerRadius to outerRadius in pixels. startAngle and sweepLength refer to the starting angle and the extent of the arc, and are in radians [0..2pi].

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { Pen.translate(100, 100); 1000.do{ // set the Color Pen.color = Color.green(rrand(0.0, 1), rrand(0.0, 0.5)); Pen.addAnnularWedge( (100.rand)@(100.rand), rrand(10, 50), rrand(51, 100), 2pi.rand, 2pi.rand ); Pen.perform([\stroke, \fill].choose); } }; w.refresh; )

.addRect

Adds a Rect to the drawing.

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { 80.do{ // set the Color Pen.color = Color.green(rrand(0.0, 1), rrand(0.0, 0.5)); Pen.addRect( Rect(20, 20, (w.bounds.width-40).rand, (w.bounds.height-40).rand) ); Pen.perform([\stroke, \fill].choose); } }; w.refresh; )

.addOval

Adds an Oval shape that fits inside the Rect to the current path.

Draw the path

.stroke

Outline the previous defined path.

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { // set the Color Pen.strokeColor = Color.red; Pen.moveTo(200@100); Pen.lineTo(250@200); Pen.lineTo(300@200); Pen.lineTo(200@250); Pen.lineTo(100@200); Pen.lineTo(150@200); Pen.lineTo(200@100); Pen.stroke }; w.refresh; )

.fill

Fill the previous defined path.

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { // set the Color Pen.fillColor = Color.red; Pen.moveTo(200@100); Pen.lineTo(250@200); Pen.lineTo(300@200); Pen.lineTo(200@250); Pen.lineTo(100@200); Pen.lineTo(150@200); Pen.lineTo(200@100); Pen.fill }; w.refresh; )

.draw

Draw the previous defined path using any of the following options:

Arguments:

style

0	fill
1	fill using even-odd rule
2	stroke
3	fill and stroke the current path
4	fill and stroke using even-odd rule

Discussion:

.fillStroke

Fill and stroke the current path. Shortcut to the draw(3) method.

Construct and draw

These methods do not require separate calls to *stroke or *fill.

.strokeRect

Strokes a Rect into the window.

.fillRect

Draws a filled Rect into the window.

.strokeOval

Strokes an oval into the window.

.fillOval

Draws a filled oval into the window.

Gradients

.fillAxialGradient

Fills an Axial gradient.

Discussion:

example:( w = Window.new.front; w.drawFunc = { // fill the gradient Pen.addRect(w.view.bounds.insetBy(30)); Pen.fillAxialGradient(w.view.bounds.leftTop, w.view.bounds.rightBottom, Color.rand, Color.rand); }; w.refresh; )

.fillRadialGradient

Fills a Radial gradient.

Discussion:

example:( w = Window.new.front; w.drawFunc = { // fill the gradient Pen.addOval(w.view.bounds.insetBy(30)); Pen.fillRadialGradient(w.view.bounds.center, w.view.bounds.center, 0, w.bounds.width, Color.rand, Color.rand); }; w.refresh; )

Graphics State Methods

The following commands transform the graphics state, i.e. they effect all subsequent drawing commands. These transformations are cumulative, i.e. each command applies to the previous graphics state, not the original one.

.translate

Translate the coordinate system to have its origin moved by x,y

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { Pen.strokeColor = Color.blue; Pen.translate(200,100); // 0@0 is now 200@100 Pen.moveTo(0@0); Pen.lineTo(50@100); Pen.lineTo(100@100); Pen.lineTo(0@150); Pen.lineTo(-100@100); Pen.lineTo(-50@100); Pen.lineTo(0@0); Pen.stroke }; w.refresh; )

Cumulative translations:( w = Window.new.front; w.view.background_(Color.clear); w.drawFunc = { Pen.strokeColor = Color.black; 35.do { // draw 35 lines Pen.moveTo(0@0); Pen.lineTo(50@350); Pen.translate(10, 0); // shift 10 to the right every time Pen.stroke } }; w.refresh; )

.scale

Scales subsequent drawing. x and y are scaling factors (i.e. 1 is normal, 2 is double size, etc.).

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { Pen.strokeColor = Color.green; Pen.translate(200,100); Pen.scale(0.5, 2); Pen.moveTo(0@0); // you have to set a starting point... Pen.lineTo(50@100); Pen.lineTo(100@100); Pen.lineTo(0@150); Pen.lineTo(-100@100); Pen.lineTo(-50@100); Pen.lineTo(0@0); Pen.stroke }; w.refresh; )

.skew

Skews subsequent drawing. x and y are skewing factors (i.e. 1 is normal).

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { Pen.fillColor = Color.green(0.5, 0.8); Pen.translate(200,100); Pen.skew(0.5, 0.2); Pen.moveTo(0@0); // you have to set a starting point... Pen.lineTo(50@100); Pen.lineTo(100@100); Pen.lineTo(0@150); Pen.lineTo(-100@100); Pen.lineTo(-50@100); Pen.lineTo(0@0); Pen.fill }; w.refresh; )

.rotate

Rotates subsequent drawing around the Point x@y by the amount angle in radians [0..2pi].

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); c = 0; w.drawFunc = { Pen.translate(220, 200); 10.do({ Pen.translate(0,10); Pen.fillColor = Color.hsv(c.fold(0, 1), 1, 1, 0.5); Pen.moveTo(0@0); // you have to set a starting point... Pen.lineTo(50@100); Pen.lineTo(100@100); Pen.lineTo(0@150); Pen.lineTo(-100@100); Pen.lineTo(-50@100); Pen.lineTo(0@0); Pen.fill; Pen.rotate(0.2pi); c = c + 0.1; }); }; w.refresh; )

.matrix

Gets or sets the coordinate system transformation matrix.

See Matrix example for an example.

Arguments:

matrixArray

An array of the form [ zoomX, shearingY, shearingX, zoomY, translateX, translateY ]

.width

Sets the width of the Pen for the whole stroke

.use

Draw function, and then revert to the previous graphics state. This allows you to make complex transformations of the graphics state without having to explicitly revert to get back to 'normal'.

Discussion:

example:( // modified by an example of Stefan Wittwer w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { //paint origin Pen.fillColor = Color.gray(0, 0.5); Pen.addArc(0@0, 20, 0, 2pi); Pen.fill; Pen.width = 10; Pen.use { // draw something complex... Pen.width = 0.5; Pen.translate(100,100); Pen.fillColor = Color.blue; Pen.addArc(0@0, 10, 0, 2pi); Pen.fill; 20.do{ Pen.moveTo(0@0); Pen.lineTo(100@0); Pen.strokeColor = Color.red(0.8, rrand(0.7, 1)); Pen.stroke; Pen.skew(0, 0.1); }; }; // now go on with all params as before // translation, skewing, width, and color modifications do not apply Pen.line(10@120, 300@120); Pen.stroke; }; w.refresh )

.path

Make a path, consisting of the drawing made in function.

NOTE: Unfortunately not working for now... (there's no Pen.endPath which currently is used in this method)

.beginPath

Discard any previous path.

.beginTransparencyLayer

Begins a new transparency layer. Transparency layers are useful when you want to apply an effect to a group of objects or create a composite graphic. See Transparency layer example.

.endTransparencyLayer

Ends the current transparency layer.

.clip

Use the previously defined path as a clipping path.

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); w.drawFunc = { // outline the clipping path Pen.moveTo(110@110); Pen.lineTo(290@110); Pen.lineTo(290@240); Pen.lineTo(110@240); Pen.lineTo(110@110); // now clip Pen.clip; // everything else we draw is now clipped Pen.fillColor = Color.yellow; Pen.fillRect(Rect(0,0,400,400)); Pen.fillColor = Color.red; Pen.moveTo(200@100); Pen.lineTo(250@200); Pen.lineTo(300@200); Pen.lineTo(200@250); Pen.lineTo(100@200); Pen.lineTo(150@200); Pen.fill; }; w.refresh; )

.smoothing

Turns on/off anti-aliasing.

Discussion:

example:( var w = Window("smoothing", Rect(100, 200, 500, 300)).front; w.view.background_(Color.white); w.drawFunc = { |v| Pen.strokeColor = Color.grey(0.25); Pen.smoothing_(false); //no anti-aliasing 50.do{|i| Pen.moveTo(50@50.rrand(250)); Pen.lineTo(250@50.rrand(250)); }; Pen.stroke; Pen.smoothing_(true); //anti-aliasing (default) 50.do{|i| Pen.moveTo(250@50.rrand(250)); Pen.lineTo(450@50.rrand(250)); }; Pen.stroke; }; )

.setShadow

Will fill the current path with a shadow. You should use this option between Pen.push / Pen.pop (or Pen.use)

.joinStyle

Set the lines joining style according to the defined options:

0	miter
1	round
2	bevel

.capStyle

Set the lines joining style according to the defined options:

0	butt
1	round
2	square

Discussion:

example:( w = Window.new.front; w.view.background_(Color.white); StaticText(w, Rect(0,0,200,20)) .string_(" Change Line Cap & Join Styles: "); y = PopUpMenu(w, Rect(200,0,130,20)) .items_(["Butt - Miter", "Round - Round", "Square - Bevel"]) .action_({w.refresh}); w.drawFunc = { Pen.strokeColor = Color.red; Pen.width_(8.0); Pen.capStyle_(y.value); Pen.joinStyle_(y.value); Pen.moveTo(200@100); Pen.lineTo(250@200); Pen.lineTo(300@200); Pen.lineTo(200@250); Pen.lineTo(100@200); Pen.lineTo(150@200); Pen.lineTo(200@100); Pen.stroke; }; w.refresh; )

.alpha

Set the opacity level.

.blendMode

Set the blending mode to use. See Blending modes for more information.

.lineDash

Set the line dash pattern. pattern should be a FloatArray of values that specify the lengths of the painted segments and not painted segments.

.drawImage

Draw a bitmap image using the Image class.

Discussion:

example:( w = Window.new.front; w.view.background = Color.red; i = Image.open(SCDoc.helpSourceDir +/+ "images/Swamp.png"); w.drawFunc_({ Pen.drawImage( Point(140, 140), i, operation: 'sourceOver', opacity:1); }); )

Inherited class methods

Instance Methods

Inherited instance methods

Examples

Simple rotating and scaling:( w = Window("Pen Rotation and Scaling", Rect(128, 64, 360, 360)); w.drawFunc = { Pen.use { // use the same rect for everything, just scale and rotate var r = Rect(0,0,200,80); Pen.fillColor = Color.black; // offset all subsequent co-ordinates Pen.translate(80,20); Pen.fillRect(r); Pen.fillColor = Color.red; // scale all subsequent co-ordinates Pen.scale(0.8, 0.8); Pen.translate(8,10); // rotate all subsequent co-ordinates Pen.rotate(0.1pi); Pen.fillRect(r); Pen.strokeColor = Color.blue; // lather, rinse, repeat Pen.scale(0.8, 0.8); Pen.rotate(0.1pi); Pen.width = 3; Pen.strokeRect(r); Pen.fillColor = Color.yellow(1,0.5); Pen.scale(0.8, 0.8); Pen.rotate(0.1pi); Pen.translate(20,-20); Pen.fillOval(r); } }; w.front; )

Redraw at random interval, different every time:( var w, run = true; w = Window("my name is... panel", Rect(128, 64, 800, 800)); w.view.background = Color.white; w.onClose = { run = false; }; w.front; w.drawFunc = { Pen.use { Pen.width = 0.2; 400.do { Pen.beginPath; Pen.moveTo(Point(10.rand * 80 + 40, 10.rand * 80 + 40)); Pen.lineTo(Point(10.rand * 80 + 40, 10.rand * 80 + 40)); Pen.stroke; }; }; }; { while { run } { w.refresh; 1.0.rand.wait } }.fork(AppClock) )

( var w, run = true; w = Window("my name is... panel", Rect(128, 64, 800, 500)); w.view.background = Color.white; w.onClose = { run = false; }; w.front; w.drawFunc = { Pen.use { Pen.width = 2; 80.do { Pen.width = rrand(0,4) + 0.5; Pen.beginPath; Pen.moveTo(Point(800.rand, 500.rand)); Pen.lineTo(Point(800.rand, 500.rand)); Pen.stroke; }; }; }; { while { run } { w.refresh; 1.0.rand.wait } }.fork(AppClock) )

Animation

Uses random seed to 'store' data By reseting the seed each time the same random values and shapes are generated for each 'frame' These can then be subjected to cumulative rotation, etc., by simply incrementing the phase var.( // By James McCartney var w, h = 700, v = 700, seed, run = true, phase = 0; w = Window("wedge", Rect(40, 40, h, v), false); w.view.background = Color.rand(0,0.3); w.onClose = { run = false }; // stop the thread on close w.front; // store an initial seed value for the random generator seed = Date.seed; w.drawFunc = { Pen.width = 2; Pen.use { // reset this thread's seed for a moment thisThread.randSeed = Date.seed; // now a slight chance of a new seed or background color if (0.006.coin) { seed = Date.seed; }; if (0.02.coin) { w.view.background = Color.rand(0,0.3); }; // either revert to the stored seed or set the new one thisThread.randSeed = seed; // the random values below will be the same each time if the seed has not changed // only the phase value has advanced Pen.translate(h/2, v/2); // rotate the whole image // negative random values rotate one direction, positive the other Pen.rotate(phase * 1.0.rand2); // scale the rotated y axis in a sine pattern Pen.scale(1, 0.3 * sin(phase * 1.0.rand2 + 2pi.rand) + 0.5 ); // create a random number of annular wedges rrand(6,24).do { Pen.color = Color.rand(0.0,1.0).alpha_(rrand(0.1,0.7)); Pen.beginPath; Pen.addAnnularWedge(Point(0,0), a = rrand(60,300), a + 50.rand2, 2pi.rand + (phase * 2.0.rand2), 2pi.rand); if (0.5.coin) {Pen.stroke}{Pen.fill}; }; }; }; // fork a thread to update 20 times a second, and advance the phase each time { while { run } { w.refresh; 0.05.wait; phase = phase + 0.01pi;} }.fork(AppClock) )

( var w, phase = 0, seed = Date.seed, run = true; w = Window("my name is... panel", Rect(128, 64, 800, 800)); w.view.background = Color.blue(0.4); w.onClose = { run = false; }; w.front; w.drawFunc = { Pen.use { if (0.02.coin) { seed = Date.seed; }; thisThread.randSeed = seed; Pen.strokeColor = Color.white; 200.do { var a = 4.rand; var b = 24.rand; var r1 = 230 + (50 * a); var a1 = 2pi / 24 * b + phase; var r2 = 230 + (50 * (a + 1.rand2).fold(0,3)); var a2 = 2pi / 24 * (b + (3.rand2)).wrap(0,23) + phase; Pen.width = 0.2 + 1.0.linrand; Pen.beginPath; Pen.moveTo(Polar(r1, a1).asPoint + Point(400,400)); Pen.lineTo(Polar(r2, a2).asPoint + Point(400,400)); Pen.stroke; }; thisThread.randSeed = Date.seed; 40.do { var a = 4.rand; var b = 24.rand; var r1 = 230 + (50 * a); var a1 = 2pi / 24 * b + phase; var r2 = 230 + (50 * (a + 1.rand2).fold(0,3)); var a2 = 2pi / 24 * (b + (3.rand2)).wrap(0,23) + phase; Pen.width = 0.2 + 1.5.linrand; Pen.beginPath; Pen.moveTo(Polar(r1, a1).asPoint + Point(400,400)); Pen.lineTo(Polar(r2, a2).asPoint + Point(400,400)); Pen.stroke; }; }; }; { while { run } { w.refresh; 0.1.wait; phase = phase + (2pi/(20*24)) } }.fork(AppClock) ) ( var w, h = 800, v = 600, seed = Date.seed, phase = 0, zoom = 0.7, zoomf = 1, run = true; w = Window("affines", Rect(40, 40, h, v)); w.view.background = Color.blue(0.4); w.onClose = { run = false }; w.front; w.drawFunc = { thisThread.randSeed = Date.seed; if (0.0125.coin) { seed = Date.seed; phase = 0; zoom = 0.7; zoomf = exprand(1/1.01, 1.01); } { phase = phase + (2pi/80); zoom = zoom * zoomf; }; thisThread.randSeed = seed; Pen.use { var p1 = Point(20.rand2 + (h/2), 20.rand2 + (v/2)); var p2 = Point(20.rand2 + (h/2), 20.rand2 + (v/2)); var xscales = { exprand(2** -0.1, 2**0.1) } ! 2; var yscales = { exprand(2** -0.1, 2**0.1) } ! 2; var xlates = { 8.rand2 } ! 2; var ylates = { 8.rand2 } ! 2; var rots = { 2pi.rand + phase } ! 2; var xform; xscales = (xscales ++ (1/xscales)) * 1; yscales = (yscales ++ (1/yscales)) * 1; xlates = xlates ++ xlates.neg; ylates = ylates ++ xlates.neg; rots = rots ++ rots.neg; xform = {|i| [xlates[i], ylates[i], rots[i], xscales[i], yscales[i]] } ! 4; Pen.strokeColor = Color.grey(1,0.5); Pen.width = 8.linrand + 1; Pen.translate(400, 400); Pen.scale(zoom, zoom); Pen.translate(-400, -400); 1200.do { var p, rot, xlate, ylate, xscale, yscale; Pen.width = 8.linrand + 1; Pen.beginPath; #rot, xlate, ylate, xscale, yscale = xform.choose; Pen.translate(xlate, ylate); Pen.rotate(rot, h/2, v/2); Pen.scale(xscale, yscale); Pen.moveTo(p1); Pen.lineTo(p2); Pen.stroke; }; }; }; { while { run } { w.refresh; 0.05.wait; } }.fork(AppClock) )

Matrix example

(
var controlWindow, w;
var r, a, b, c, d, matrix = [1, 0, 0, 1, 10, 10];
var sliders, spex, name;

w = Window.new.front;
w.view.background_(Color.white);

// create a controller-window
controlWindow = Window("matrix controls", Rect(400,200,350,120));
controlWindow.front;

// determine the rectangle to be drawn
r = Rect.fromPoints(a = 0 @ 0, c = 180 @ 180);
b = r.leftBottom;
d = r.rightTop;

// the drawFunc
w.drawFunc = {
    Pen.strokeColor = Color.red;
    Pen.matrix = matrix;
    Pen.width = 5;
    Pen.strokeRect(r);
    Pen.strokeOval(r);
    Pen.color = Color.blue;
    Pen.width = 0.1;
    Pen.line(a, c);
    Pen.line(b, d);
    Pen.stroke;

Pen.font = Font( "Helvetica-Bold", 12 );
    Pen.stringAtPoint( "A", a - 6 );
    Pen.stringAtPoint( "B", b - 6 );
    Pen.stringAtPoint( "C", c - (0@6) );
    Pen.stringAtPoint( "D", d - (0@6) );

Pen.font = Font( "Helvetica", 10 );
    Pen.stringInRect( "a matrix test", r.moveBy( 50, 50 ));
};

controlWindow.view.decorator = sliders = FlowLayout(controlWindow.view.bounds);
spex = [
    [0, 2.0].asSpec,
    [0, 2.0].asSpec,
    [0, 2.0].asSpec,
    [0, 2.0].asSpec,
    [0, 200.0].asSpec,
    [0, 200.0].asSpec
];
name = #[zoomX, shearingY, shearingX, zoomY, translateX, translateY];
6.do { |i|
    EZSlider(controlWindow, 300 @ 14, name[i], spex[i], { |ez| var val;
            val = ez.value;
            [i, val.round(10e-4)].postln;
            matrix.put(i, val);
            w.refresh; // reevaluate drawFunc function
    }, matrix[i]);
    sliders.nextLine;
};
w.refresh;
)

Transparency layer example

(
w = Window.new("Transparency Layer test", Rect(400,400,430,450)).front;
w.drawFunc = {
    Color.blue.setStroke;

Pen.use {
    Pen.setShadow(2@2, 10, Color.black);
    Pen.beginTransparencyLayer;

Color.red.setFill;
    Pen.addOval(Rect(20,40,100,100));
    Pen.fill;

Color.green.setFill;
    Pen.addOval(Rect(30,70,100,100));
    Pen.fill;

Color.blue.setFill;
    Pen.addOval(Rect(60,40,100,100));
    Pen.fill;

"With Transparency Layer".drawCenteredIn(Rect(30, 40, 100, 100), Font.default, Color.white);
    Pen.endTransparencyLayer;
    };

Pen.use {
    Pen.translate(200, 0);
    Pen.setShadow(2@2, 10, Color.black);

Color.red.setFill;
    Pen.addOval(Rect(20,40,100,100));
    Pen.fill;

Color.green.setFill;
    Pen.addOval(Rect(30,70,100,100));
    Pen.fill;

Color.blue.setFill;
    Pen.addOval(Rect(60,40,100,100));
    Pen.fill;

"Without Transparency Layer".drawCenteredIn(Rect(30, 40, 100, 100), Font.default, Color.white);
    };

Pen.use {
        Pen.translate(0, 200);
        Pen.setShadow(2@2, 10, Color.black);
        Pen.beginTransparencyLayer;

Pen.push;
        Pen.addOval(Rect(20,40,170,170));
        Pen.fillAxialGradient(w.view.bounds.leftTop, w.view.bounds.rightBottom, Color.rand, Color.rand);
        Pen.pop;

"With Transparency Layer".drawCenteredIn(Rect(20,40,170,170), Font.default, Color.white);

Pen.endTransparencyLayer;
    };

Pen.use {
        Pen.translate(200, 200);
        Pen.setShadow(2@2, 10, Color.black);
        Pen.addOval(Rect(20,40,170,170));
        Pen.fillAxialGradient(w.view.bounds.leftTop, w.view.bounds.rightBottom, Color.rand, Color.rand);

"Without Transparency Layer".drawCenteredIn(Rect(20,40,170,170), Font.default, Color.white);
    };
};
w.refresh;
)

Blending modes

/*
different blend modes:
--------------------
0 - Normal
1 - Multiply
2 - Screen
3 - Overlay
4 - Darken
5 - Lighten
6 - ColorDodge
7 - ColorBurn
8 - SoftLight
9 - HardLight
10 - Difference
11 - Exclusion
12 - Hue
13 - Saturation
14 - Color
15 - Luminosity
16 - Clear
17 - Copy
18 - SourceIn
19 - SourceOut
20 - SourceATop
21 - DestinationOver
22 - DestinationIn
23 - DestinationATop
24 - XOR
25 - PlusDarker
26 - PlusLighter
*/

(
    var blendMode=0, blendString="Normal";
    w = Window.new.front;
    m = PopUpMenu(w, Rect(10, w.view.bounds.height - 30, 150, 20));
    m.items = [
        "0 - Normal",
        "1 - Multiply",
        "2 - Screen",
        "3 - Overlay",
        "4 - Darken",
        "5 - Lighten",
        "6 - ColorDodge",
        "7 - ColorBurn",
        "8 - SoftLight",
        "9 - HardLight",
        "10 - Difference",
        "11 - Exclusion",
        "12 - Hue",
        "13 - Saturation",
        "14 - Color",
        "15 - Luminosity"
    ];

m.action_({|view|
        blendMode = view.value;
        blendString = view.items.at(blendMode);
        w.refresh;
    });
    w.drawFunc = {
        80.do{|i|
            Pen.use {
            Pen.blendMode_(blendMode);
            Pen.color = Color.green(0.6, 0.10);
            Pen.addRect(
                Rect(20, 20, 20 + (i*4), 20 + (i*4));
            );
            Pen.fill;
            };
        }
    };
    w.refresh;
)

helpfile source: https://github.com/supercollider/supercollider/tree/3.13/HelpSource/Classes/Pen.schelp
link::Classes/Pen::