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08 - Fun with HTML5 Canvas Expand file tree Collapse file tree 1 file changed +54
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lines changed Original file line number Diff line number Diff line change 77< body >
88< canvas id ="draw " width ="800 " height ="800 "> </ canvas >
99< script >
10+ const canvas = document . querySelector ( '#draw' ) ;
11+ const ctx = canvas . getContext ( '2d' ) ;
12+ canvas . width = window . innerWidth ;
13+ canvas . height = window . innerHeight ;
14+ ctx . strokeStyle = '#BADA55' ;
15+ ctx . lineJoin = 'round' ;
16+ ctx . lineCap = 'round' ;
17+ ctx . lineWidth = 100 ;
18+ // ctx.globalCompositeOperation = 'multiply';
19+
20+ let isDrawing = false ;
21+ let lastX = 0 ;
22+ let lastY = 0 ;
23+ let hue = 0 ;
24+ let direction = true ;
25+
26+ function draw ( e ) {
27+ if ( ! isDrawing ) return ; // stop the fn from running when they are not moused down
28+ console . log ( e ) ;
29+ ctx . strokeStyle = `hsl(${ hue } , 100%, 50%)` ;
30+ ctx . beginPath ( ) ;
31+ // start from
32+ ctx . moveTo ( lastX , lastY ) ;
33+ // go to
34+ ctx . lineTo ( e . offsetX , e . offsetY ) ;
35+ ctx . stroke ( ) ;
36+ [ lastX , lastY ] = [ e . offsetX , e . offsetY ] ;
37+
38+ hue ++ ;
39+ if ( hue >= 360 ) {
40+ hue = 0 ;
41+ }
42+ if ( ctx . lineWidth >= 100 || ctx . lineWidth <= 1 ) {
43+ direction = ! direction ;
44+ }
45+
46+ if ( direction ) {
47+ ctx . lineWidth ++ ;
48+ } else {
49+ ctx . lineWidth -- ;
50+ }
51+
52+ }
53+
54+ canvas . addEventListener ( 'mousedown' , ( e ) => {
55+ isDrawing = true ;
56+ [ lastX , lastY ] = [ e . offsetX , e . offsetY ] ;
57+ } ) ;
58+
59+
60+ canvas . addEventListener ( 'mousemove' , draw ) ;
61+ canvas . addEventListener ( 'mouseup' , ( ) => isDrawing = false ) ;
62+ canvas . addEventListener ( 'mouseout' , ( ) => isDrawing = false ) ;
63+
1064</ script >
1165
1266< style >
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