pf1Bit

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3 total messages Started by Vinko Tue, 22 Apr 2003 17:39

#16860

Author: Vinko
Date: Tue, 22 Apr 2003 17:39

11 lines
1250 bytes

Hi!

How to read bitmap pixels values, if bitmap color depth is only 1 bit (black
& white)?
Canvas->Pixels[x][y] can simply read pixel value, but it is too slow.
I would like to read pixels with ScanLine method. If bitmap is pf8bit,
pf24bit or pf32bit
i can do that, but with pf1bit, without luck. I also tryed with bits
shifting.

THANK YOU, Saso

Re: pf1Bit

#16864

Author: Martin Moeller
Date: Tue, 22 Apr 2003 20:22

7 lines
1114 bytes

"Vinko" <digitalsv@email.si> wrote:
> I also tryed with bits shifting.

If not by shift, you could try masking and testing the result.

Martin

Re: pf1Bit

#16872

Author: Damon Chandler (TeamB)
Date: Wed, 23 Apr 2003 06:19

35 lines
1772 bytes

Hi Vinko,
> How to read bitmap pixels values, if bitmap color depth is only 1 
> bit (black & white)?

You can use the TBitmap::ScanLine property (BCB3+) along with the following
function to read a bit (pixel) of each byte (8 pixels)...

inline bool get_bit(
   unsigned char const& byte_var,
   unsigned char n // zero-based, from left
  )
{
  return (byte_var << n) & 128;
}

Here's a brief example...

  Graphics::TBitmap& Bitmap = *Image1->Picture->Bitmap;
  SIZE const SBmp = {Bitmap.Width, Bitmap.Height};

  for (int y = 0; y < SBmp.cy; ++y)
  {
    unsigned char* pRow =
      static_cast<unsigned char*>(Bitmap.ScanLine[y]);
    for (int x = 0; x < SBmp.cx; ++x)
    {
      bool const is_set = get_bit(pRow[x], N); // define N b/n [0, 7]
      // ...
    }
  }

HTH,
-- 
Damon (TeamB)
BCBCAQ--http://bcbcaq.bytamin-c.com

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