Created
June 13, 2012 21:50
-
-
Save getify/2926699 to your computer and use it in GitHub Desktop.
non-rectangular (line and circle) clears in canvas
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| /* | |
| To see a demo of these in use, check out: http://test.getify.com/test-canvas-clear-alt.html | |
| Example uses: | |
| */ | |
| clearCircle(context,/*x=*/120,/*y=*/80,/*radius=*/60); | |
| clearLineSquared(context,/*x1=*/10,/*y1=*/10,/*x2=*/53,/*y2=*/67,/*thickness=*/5); | |
| clearLineRounded(context,/*x1=*/15,/*y1=*/100,/*x2=*/90,/*y2=*/170,/*thickness=*/10); | |
| clearLineRounded(context,/*x1=*/90,/*y1=*/170,/*x2=*/160,/*y2=*/150,/*thickness=*/10); | |
| // code | |
| function dist(x1,y1,x2,y2) { | |
| x2-=x1; y2-=y1; | |
| return Math.sqrt((x2*x2) + (y2*y2)); | |
| } | |
| function clearCircle(context,x,y,radius) { | |
| context.save(); | |
| context.beginPath(); | |
| context.arc(x, y, radius, 0, 2*Math.PI, true); | |
| context.clip(); | |
| context.clearRect(x-radius,y-radius,radius*2,radius*2); | |
| context.restore(); | |
| } | |
| function clearLineSquared(context,x1,y1,x2,y2,thickness) { | |
| var tmp, length; | |
| // swap coordinate pairs if x-coordinates are RTL to make them LTR | |
| if (x2 < x1) { | |
| tmp = x1; x1 = x2; x2 = tmp; | |
| tmp = y1; y1 = y2; y2 = tmp; | |
| } | |
| length = dist(x1,y1,x2,y2); | |
| context.save(); | |
| context.translate(x1,y1); | |
| context.rotate(Math.atan2(y2-y1,x2-x1)); | |
| context.clearRect(0,0,length,thickness); | |
| context.restore(); | |
| } | |
| function clearLineRounded(context,x1,y1,x2,y2,thickness) { | |
| if (thickness <= 2) { | |
| clearLineSquared(context,x1,y1,x2,y2,thickness); | |
| return; | |
| } | |
| var tmp, half_thickness = thickness / 2, length, | |
| PI15 = 1.5 * Math.PI, PI05 = 0.5 * Math.PI | |
| ; | |
| // swap coordinate pairs if x-coordinates are RTL to make them LTR | |
| if (x2 < x1) { | |
| tmp = x1; x1 = x2; x2 = tmp; | |
| tmp = y1; y1 = y2; y2 = tmp; | |
| } | |
| length = dist(x1,y1,x2,y2); | |
| context.save(); | |
| context.translate(x1,y1); | |
| context.rotate(Math.atan2(y2-y1,x2-x1)); | |
| x1 = 0; | |
| y1 = 0; | |
| x2 = length - 1; | |
| y2 = 0; | |
| // draw a complex "line" shape with rounded corner caps | |
| context.moveTo(x1,y1-half_thickness); | |
| context.lineTo(x2,y2-half_thickness); | |
| context.arc(x2,y2,half_thickness,PI15,PI05,false); | |
| context.lineTo(x1,y1-half_thickness+thickness); | |
| context.arc(x1,y1,half_thickness,PI05,PI15,false); | |
| context.closePath(); | |
| x1 -= half_thickness; | |
| y1 -= half_thickness; | |
| context.clip(); | |
| context.clearRect(x1,y1,length+thickness,thickness); | |
| context.restore(); | |
| } |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Thank you 👍