2. for ( var x = 0; x < canvasData.width; x++) {

3. for ( var y = 0; y < canvasData.height; y++) {

5. // Index of the pixel in the array

6. var idx = (x + y * canvasData.width) * 4;

7. var r = canvasData.data[idx + 0];

8. var g = canvasData.data[idx + 1];

9. var b = canvasData.data[idx + 2];

10. var gray = .299 * r + .587 * g + .114 * b;

12. // assign gray scale value

13. canvasData.data[idx + 0] = gray; // Red channel

14. canvasData.data[idx + 1] = gray; // Green channel

15. canvasData.data[idx + 2] = gray; // Blue channel

16. canvasData.data[idx + 3] = 255; // Alpha channel

17. // 加上黑色的边框

18. if(x < 8 || y < 8 || x > (canvasData.width - 8) || y > (canvasData.height - 8))

19. {

20. canvasData.data[idx + 0] = 0;

21. canvasData.data[idx + 1] = 0;

22. canvasData.data[idx + 2] = 0;

23. }

24. }

25. }

3.把新的图像数据写入canvas

1. context.putImageData(canvasData, 0, 0);

4.效果预览

点这里看预览