Converting from signed char to unsigned char and back again?

Question

I\'m working with JNI and have an array of type jbyte, where jbyte is represented as an signed char i.e. ranging from -128 to 127. The jbytes represent image pixels. For ima

Answer 1

Yes this is safe.

The c language uses a feature called integer promotion to increase the number of bits in a value before performing calculations. Therefore your CLAMP255 macro will operate at integer (probably 32 bit) precision. The result is assigned to a jbyte, which reduces the integer precision back to 8 bits fit in to the jbyte.