Thread: GetPixel return value

I have an example in petzold (chapter 5, basic drawing) that was something like this (to implement the GetPixel function):

crColor = GetPixel(hdc, x, y)

I know what the parameters are for GetPixel and I understand what the function does, but what type is the return value to assign to?

Thanks.

--Garfield the Programmer

It's a COLORREF, which is a 32bit variable packed with a RGB value. The bytes are 00BBGGRR.

So I would use a long int data type? BTW, what is the equivalent of long int in Windows programming?

Thanks.

--Garfield

Or would the data type be COLORREF? Would it be this:

Code:

COLORREF     crColor;

crColor = GetPixel(hdc, x, y);

Thanks.

--Garfield

Oh (sorry for all this posting), can you still answer my 'long int' question? Thanks.

Yes, COLORREF is a typedef of DWORD, which is a typedef of unsigned long, but you'd use a COLORREF variable so anyone looking at your code knows what it is. Also, if the sizeof unsigned long changes then COLORREF may no longer be a typedef of unsigned long, so if you were compliing code in this enviroment it may not be correct (in future versions of windows/win32api).

There are lots of different typedef's of a long int/unsigned long. LONG and ULONG are the most obvious, but if you're not sure there's nothing stopping you using a normal C long. Also if you're using MSVC and you enable the option to generate browse info anytime you're not sure of a typedef(or any function, define, etc), place the caret on it and press F12 and you'll be shown the header file where it's typedef'd.

Thanks, zen!

Ahhhh, F12.
(Beats the right click & go to definition/ref)

My new friend. Come and play with me and F1.

(You learn somethig new everyday. Now I can go home and forget it)