# Composition Modes
Composition allows you to draw a shape and blend it with the existing pixels. The canvas supports several composition modes using the globalCompositeOperation(mode)
operations. For instance:
source-over
source-in
source-out
source-atop
Let's begin with a short example demonstrating the exclusive or composition:
onPaint: {
var ctx = getContext("2d")
ctx.globalCompositeOperation = "xor"
ctx.fillStyle = "#33a9ff"
for(var i=0; i<40; i++) {
ctx.beginPath()
ctx.arc(Math.random()*400, Math.random()*200, 20, 0, 2*Math.PI)
ctx.closePath()
ctx.fill()
}
}
The example below will demonstrate all composition modes by iterating over them and combining a rectangle and a circle. You can find the resulting output below the source code.
property var operation : [
'source-over', 'source-in', 'source-over',
'source-atop', 'destination-over', 'destination-in',
'destination-out', 'destination-atop', 'lighter',
'copy', 'xor', 'qt-clear', 'qt-destination',
'qt-multiply', 'qt-screen', 'qt-overlay', 'qt-darken',
'qt-lighten', 'qt-color-dodge', 'qt-color-burn',
'qt-hard-light', 'qt-soft-light', 'qt-difference',
'qt-exclusion'
]
onPaint: {
var ctx = getContext('2d')
for(var i=0; i<operation.length; i++) {
var dx = Math.floor(i%6)*100
var dy = Math.floor(i/6)*100
ctx.save()
ctx.fillStyle = '#33a9ff'
ctx.fillRect(10+dx,10+dy,60,60)
ctx.globalCompositeOperation = root.operation[i]
ctx.fillStyle = '#ff33a9'
ctx.globalAlpha = 0.75
ctx.beginPath()
ctx.arc(60+dx, 60+dy, 30, 0, 2*Math.PI)
ctx.closePath()
ctx.fill()
ctx.restore()
}
}