Imagesc() doesn't convert arrays to images. Images are arrays.
If you have something that needs to be normalized with respect to its extrema, use normalize() or mat2gray().
That said, a routine cause of errors is normalizing to extrema when there is some prevailing convention for the nominal range of the data. If so, specify the normalization limits in the call to normalize() or mat2gray().
Let's say you have an array which is some sort of angle map. The nominal range of values is 0 to 360.
A = [69 266 87 331 97 276 68 103 32 208];
B = mat2gray(A)
B =
0.1237 0.7826 0.1839 1.0000 0.2174 0.8161 0.1204 0.2375 0 0.5886
Normalizing to the data extrema eliminates all information describing the scale and position of the data with respect to the nominal limits. Normalizing to the nominal limits retains that information.
C = mat2gray(A,[0 360])
C =
0.1917 0.7389 0.2417 0.9194 0.2694 0.7667 0.1889 0.2861 0.0889 0.5778
You'll have to decide what suits your needs.