11<!DOCTYPE html>
22< html lang ="en ">
3+
34< head >
45 < meta charset ="UTF-8 ">
56 < title > HTML5 Canvas</ title >
67</ head >
8+
79< body >
8- < canvas id ="draw " width ="800 " height ="800 "> </ canvas >
9- < script >
10- </ script >
10+ < canvas id ="draw " width ="800 " height ="800 "> </ canvas >
11+ < script >
12+ const canvas = document . querySelector ( '#draw' ) ;
13+ const ctx = canvas . getContext ( '2d' ) ;
14+ canvas . width = window . innerWidth ;
15+ canvas . height = window . innerHeight ;
16+ ctx . strokeStyle = '#BADA55' ;
17+ ctx . lineJoin = 'round' ;
18+ ctx . lineCap = 'round' ;
19+
20+ let isDrawing = false ;
21+ let lastX = 0 ;
22+ let lastY = 0 ;
23+ let hue = 0 ;
24+ let direction = false ;
1125
12- < style >
13- html , body {
14- margin : 0 ;
15- }
16- </ style >
26+ function draw ( e ) {
27+ if ( ! isDrawing ) return ;
28+ console . log ( e ) ;
29+ ctx . strokeStyle = `hsl(${ hue } ,100%,50%)` ;
30+ ctx . beginPath ( ) ;
31+ ctx . moveTo ( lastX , lastY ) ;
32+ ctx . lineTo ( e . offsetX , e . offsetY ) ;
33+ ctx . stroke ( ) ;
34+ [ lastX , lastY ] = [ e . offsetX , e . offsetY ] ;
35+ hue ++ ;
36+ if ( hue >= 360 ) {
37+ hue = 0 ;
38+ }
39+ if ( ctx . lineWidth >= 100 || ctx . lineWidth <= 1 ) {
40+ direction = ! direction ;
41+ }
42+ if ( direction ) {
43+ ctx . lineWidth ++ ;
44+ } else {
45+ ctx . lineWidth -- ;
46+ }
47+ }
48+
49+ canvas . addEventListener ( 'mousedown' , ( e ) => {
50+ isDrawing = true ;
51+ [ lastX , lastY ] = [ e . offsetX , e . offsetY ] ;
52+ } )
53+ canvas . addEventListener ( 'mousemove' , draw ) ;
54+ canvas . addEventListener ( 'mouseup' , ( ) => isDrawing = false )
55+ canvas . addEventListener ( 'mouseout' , ( ) => isDrawing = false )
56+ </ script >
57+
58+ < style >
59+ html ,
60+ body {
61+ margin : 0 ;
62+ }
63+ </ style >
1764
1865</ body >
19- </ html >
66+
67+ </ html >
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