how can i change the rgb order?

i read txt file which contains r,g,b information. (r,g,b * 66049) ex.[r1, g1, b1; r2, g2, b2; ...] and then convert as 257,257,3 dimension to draw image.

the problem is when i draw this image, i check information values by using data cursor.

but pixel's information are fixed by vertically. i have 257*257 dimension images

------------------------- r1 g1 b1 | |r2 g2 b2 | | | |________________________

but i want to draw

------------------------- r1 g1 b1 r2 b2 g2 | | | | | |_______________________

how can i do this?