But what GetPixelFormat does not explicitly return is the number of
bits you need to shift each RGB component to make your 16-bit value.

Well, the DD docs has a neat function that does this for you:

code:

WORD GetNumberOfBits(DWORD dwMask) { WORD wBits = 0;     while(dwMask) {    dwMask = dwMask & (dwMask - 1);    wBits++;     } return wBits;}

What this does is count the number of '1' bits in a mask. So,
a blue mask of 0x001F will return a value of 5 (only 5 bits are set)

Save these mask bit counts in variables too. These are needed to
finally determine how many bits you need to shift each RGB component.

It'll look something like this:
------
DDPIXELFORMAT ddpf;
ZeroMemory( &ddpf, sizeof(DDPIXELFORMAT) );
ddpf.dwSize = sizeof(DDPIXELFORMAT);

surface->GetPixelFormat(&ddpf);

red_mask = ddpf.dwRBitMask;
green_mask = ddpf.dwGBitMask;
blue_mask = ddpf.dwBBitMask;

red_bits = GetNumberOfBits(red_mask);
green_bits = GetNumberOfBits(green_mask);
blue_bits = GetNumberOfBits(blue_mask);

blue_shift = 0;
green_shift = blue_bits;
red_shift = blue_bits + green_bits;

------

That's all you need to do! Now you can reference these variables in
a 16bit macro or function and you are good to go. So use the masks
to extract RGB components, and use the shifts to make a 16-bit color
value.

Don't use constant values directly, it will only make your code less
compatible.

Reaver

[This message has been edited by Reaver (edited November 01, 1999).]

B = (col & 0x1F) << 3;
G = ((col >> 5) & 0x3F) << 2;
R = ((col >> 11) & 0x1F) << 3;

This doesn't quite work though! It results in these ranges.

R = 0-248
G = 0-252
B = 0-248

Close enough!

void GetRGB()
{
m_iB = ( col & m_dwBMask ) << 3;
m_iG = ( (col & m_dwGMask ) >> m_wGShift ) << 2;
m_iR = ( (col & m_dwRMask ) >> m_wRShift ) << 3;
}

void SetPixelFormat( LPDIRECTSURFACE4 bla )
{
m_dwRMask = ddpixel.dwRBitMask;
m_dwGMask = ddpixel.dwGBitMask;
m_dwBMask = ddpixel.dwBBitMask;

WORD wRBits = GetNumberOfBits( m_dwRMask );
WORD wGBits = GetNumberOfBits( m_dwGMask );
WORD wBBits = GetNumberOfBits( m_dwBMask );

m_wRShift = wBBits + wGBits;
m_wGShift = wBBits;
m_wBShift = 0;
}

Not this looks ok to everyone, then let's try it.
wSurf2[ y * 256 + x] = GetColor16( 255, 0, 255 );
GetRGB( wSurf2[ y * 256 + x] );
Now it should be, R = 248, G = 0, B = 248. But it's not.
It's R = 248, G = 28, B = 248. Hmmmm. I remove the << 2
and I found that G gets the value 7 when it should be 0.
Pretty much the same thing happened when I wrote (0,255,255)
it read (56,124,248). (124 can be fixed by shifting the G by
3 instead). Any ideas why this happens.

And Reaver, would the Mask and shift be correct in 24 or 32
bpp mode too, using the GetNumberOfBits thingie?

code:

 WORD  GetColor16(BYTE r, BYTE g, BYTE b) {    return (WORD)( (((r>>(8-wRBits))&31) << m_wRShift) | (((g>>(8-wGBits))&31) << m_wGShift) | ((b>>(8-wBBits))&31) ); }

I hope that came out right.

Hmmm, or try this:

code:

 WORD  GetColor16(BYTE r, BYTE g, BYTE b) {    return (WORD)( ((r>>(8-wRBits)) << m_wRShift) | ((g>>(8-wGBits)) << m_wGShift) | (b>>(8-wBBits)) ); }

I don't know if that will do much visually, but I just remembered I put in
the &31 part because I want all color to clamp to 555, even though it might be 565.
Or you could try substituting &63 for the &31 part in the green component.
I never tried this, it might not work right.

If that doesn't work, make sure you have everything setup correctly, write
out your masks values, shift values, and bit count values. Make sure it is
all correct for 16-bit 565.

And, I think you don't need to use GetNumberOfBits or figure out
how bits to shift with 24-bit, because it usually only has one format.
At least I hope so. Always 888 for 24-bit. I think 32-bit can be
2-10-10-10 or 8-8-8-8. I never tested it with anything else than 16-bit,
but I would guess it would still give you the same results.

Reaver

[This message has been edited by Reaver (edited November 01, 1999).]

Rock

How do I extract each color components of a 16bit 565 color?
I tried this:
B = col & 0x1F;
G = (col >> 5) & 0x3F;
R = (col >> 11) & 0x1F;
But it didn't work very well, color values are just between 0-31, I want them 0-255.
There must be some way, please help.

TIA, Tobias