Connect two pixels

Connect two pixels in an image with the desired graylevel

Command line
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result = func_DrawLine(Img, X1, Y1, X2, Y2)
input: Img : the original image.
(X1, Y1), (X2, Y2) : points to connect.
nG : the gray level of the line.
output: result

Note
----
Img can be anything
(X1, Y1), (X2, Y2) should be NOT be OUT of the Img

The computation cost of this program is around half as Cubas's [1]
[1] As for Cubas's code, please refer
http://www.mathworks.com/matlabcentral/fileexchange/loadFile.do?objectId=4177

Example
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result = func_DrawLine(zeros(5, 10), 2, 1, 5, 10, 1)
result =
0 0 0 0 0 0 0 0 0 0
1 1 1 0 0 0 0 0 0 0
0 0 0 1 1 1 0 0 0 0
0 0 0 0 0 0 1 1 1 0
0 0 0 0 0 0 0 0 0 1