| <html> |
| <body> |
| <canvas id="canvas" width="600" height="100" ></canvas> |
| <script> |
| var canvas = document.getElementById("canvas"); |
| var context = canvas.getContext("2d"); |
| |
| var offscreenCanvas1 = new OffscreenCanvas(100, 100); |
| var ctx1 = offscreenCanvas1.getContext('2d'); |
| ctx1.fillStyle = 'green'; |
| ctx1.fillRect(0, 0, 100, 100); |
| var offscreenCanvas2 = new OffscreenCanvas(100, 100); |
| var ctx2 = offscreenCanvas2.getContext('2d'); |
| |
| ctx2.globalAlpha = 0.0; |
| ctx2.drawImage(offscreenCanvas1, 0, 0); |
| context.drawImage(offscreenCanvas2, 0, 0, 100, 100, 0, 0, 100, 100); |
| |
| ctx2.globalAlpha = 0.2; |
| ctx2.drawImage(offscreenCanvas1, 0, 0); |
| context.drawImage(offscreenCanvas2, 0, 0, 100, 100, 100, 0, 100, 100); |
| |
| ctx2.globalAlpha = 0.4; |
| ctx2.drawImage(offscreenCanvas1, 0, 0); |
| context.drawImage(offscreenCanvas2, 0, 0, 100, 100, 200, 0, 100, 100); |
| |
| ctx2.globalAlpha = 0.6; |
| ctx2.drawImage(offscreenCanvas1, 0, 0); |
| context.drawImage(offscreenCanvas2, 0, 0, 100, 100, 300, 0, 100, 100); |
| |
| ctx2.globalAlpha = 0.8; |
| ctx2.drawImage(offscreenCanvas1, 0, 0); |
| context.drawImage(offscreenCanvas2, 0, 0, 100, 100, 400, 0, 100, 100); |
| |
| ctx2.globalAlpha = 1.0; |
| ctx2.drawImage(offscreenCanvas1, 0, 0); |
| context.drawImage(offscreenCanvas2, 0, 0, 100, 100, 500, 0, 100, 100); |
| </script> |
| </body> |
| </html> |
