CODEWITHSUNDEEP
iosobjective-c
MusiGenesis
MusiGenesis

Reputation: 75276

How to (quickly) convert float to Byte?

I have a method that processes all the pixels in a bitmap (represented as a Byte array). For each pixel, I do fairly complex calculations for each R, G and B value using a float to store the calculated value until finally converting it back to a Byte (using just a cast, and I'm certain the value in the float will always be 255.0 or less).

In trying to optimize this method, I was surprised to find that about 80% of the overall processing time was from just the casting of the three float values for R, G and B to their Byte counterparts.

Is there any kind of super-fast way of doing this (e.g.):

float Rtotal = 123.7;
float Gtotal = 7.3;
float Btotal = 221.3;

Byte Rsource = (Byte)Rtotal;
Byte Gsource = (Byte)Gtotal;
Byte Bsource = (Byte)Btotal;

Upvotes: 3

Views: 81

Answers (1)

MusiGenesis
MusiGenesis

Reputation: 75276

Ok, this is a bit odd. If I just make this change:

float Rtotal = 123.7;
float Gtotal = 7.3;
float Btotal = 221.3;

Byte Rsource = (int)Rtotal;
Byte Gsource = (int)Gtotal;
Byte Bsource = (int)Btotal;

the extra time caused by the cast to (Byte) disappears. My guess here is that the compiler is adding some kind of bounds checking to the (Byte) cast to ensure that it's within the valid range of a Byte, whereas it omits this if the cast is to int.

Upvotes: 3

Related Questions