INT1() and RGB() macro

[gelarimer]

The following code returns a warning that argsdo not match definition, because definition requireskind 1for args.

iret = RGB(180, 180, 255)

tried the following,

iret = RGB(INT1(180), INT1(180), INT1(255))

but if left most digitis set then INT1() is a negative number.

How is an unsigned 1 byte value of 255 represented in FORTRAN?

Thanks for any info.

[jimdempseyatthecove]

FORTRAN does not have unsigned integers. The values above unsigned int 128 are negative when represented as integer(1).

255 = -1, 254= -2, ... 128 = -128

One method you can consider to use is to create function like the following

INT1 function asINT1(I)
! calling arg
integer :: I
! local arg to avoid saturation
integer ::Imasked
! force modular 256
Imasked = IAND(I,255)
if(Imasked .ge. 128) then
asINT1 = INT1(256 - Imasked)
else
asINT1 = INT1(Imasked)
endif
end function asINT1

If you are certain that the input arg is always within 0 to 255 then you can remove the masking. If you do this then for the Debug configuration have conditional code insert an assertion to confirm this.

Jim Dempsey

[Jugoslav_Dujic]

...in other words, RGB function as implemented in IFWIN.lib is broken and next to unusable if it has INTEGER(1) arguments; maybe it's translated from C without much thought.

You can roll your own statement or real function with integer(4) arguments, like:

RGB(R, G, B) = MIN(R, 255) + ISHFT(MIN(G, 255), 8) + ISHFT(MIN(B, 255), 16)

...or, simpler still, use Z'BBGGRR' hex notation.

[Steven_L_Intel1]

The real problem is that CVF ignored KIND differences in the presence of an explicit interface and ifort does not (CVF's behavior was a bug.) Unfortunately, there's a lot of code that depended on the laxness and the uses of RGB is one of them. I have a request in to solve this in various ways, including making RGB a generic and adding a UINT intrinsic.

[Steven_L_Intel1]

Try this, using RGBX instead of RGB:

module rgbmod

implicit none

interface RGBX

function RGB1 (red, green, blue)
integer(4) :: RGB1
!DEC$ ATTRIBUTES DEFAULT, STDCALL, DECORATE, ALIAS:'Rgb' :: RGB1
INTEGER(1)  red
INTEGER(1)  green
INTEGER(1)  blue
end function RGB1

function RGB2 (red, green, blue)
integer(4) :: RGB2
!DEC$ ATTRIBUTES DEFAULT, STDCALL, DECORATE, ALIAS:'Rgb' :: RGB2
INTEGER(2)  red
INTEGER(2)  green
INTEGER(2)  blue
end function RGB2

function RGB4 (red, green, blue)
integer(4) :: RGB4
!DEC$ ATTRIBUTES DEFAULT, STDCALL, DECORATE, ALIAS:'Rgb' :: RGB4
INTEGER(4)  red
INTEGER(4)  green
INTEGER(4)  blue
end function RGB4

end interface RGBX

end module rgbmod

[gelarimer]

Thanks for all the replies.Very helpful code and comments.

[Steven_L_Intel1]

I fixed the code I posted - RGB returns an INTEGER(4) not INTEGER(1). Sorry for the mixup.