suoh - I think that one problem might be with your "else if". In MATLAB, there isn't a space and so this is just "elseif". The way you have it right now suggests that you have an else block followed by another if/else block which would need to be terminated with an end just like the previous two if blocks... but you only have two ends which might then be the source of the error.
For sure the last two lines are out of place and should be in the body of the block that defines the Img. And your first if block is missing an end.