Hey, easy question...

I am reading a pnm image file where each rgb value is 3 single bytes. I'm reading it into a char array. How can I then get the decimal (unsigned) value? For example, if the color is RGB(224,223,224), how can I get those into an unsigned variable as such? That is, I don't want RGB(-32,-33,-32).

I want to be able to do a comparison to see if each is within a range of values. So, for a given pixel, I'm checking if the red value is less than 225 and greater than 235 as an example. I want to be able to do

char r = 224; // stored in 8-bits = -32
if (r > 220 && r < 235)
{
// the above evauates to false because -32 is NOT > 220
}

I'm sure it's a simple newbie question.

Thanks,

Micah

If you're programming in C or C++, it *IS* a simple question - you just cast to "unsigned char".

If, on the other hand, you're programming in Java ... the answer might be equally simple ... or there might not be any easy answer. For example:

http://forum.java.sun.com/thread.jsp...sageID=2956319
http://saloon.javaranch.com/cgi-bin/...&f=33&t=007156

Oh yeah, sorry, it's c++. Problem is, when I cast to an unsigned int I get 4294967264 instead of 224

int ir = (unsigned char)r;
int ig = (unsigned char)g;
int ib = (unsigned char)b;

The key is to make sure (if you happen to be starting out with a *signed* char - either explicitly or implicitly) to make sure your cast doesn't left-fill a bunch of unneeded/unwanted "1" bits.

The way to do this is to cast to "(unsigned char)" right at the outset.

'Hope that helps .. PSM

Brilliant. That's it. Thank you so much!