how can i change pixel's data position?

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. but i want to fix data horizontally [r1 g1 b1 .......r257 g257 b257; r257 g257 b257...]

how can i do this? :(