Remove surrounding whitespace from an image

Question

I have a block of product images we received from a customer. Each product image is a picture of something and it was taken with a white background. I would like to crop a

Answer 1

Here's my (rather lengthy) solution:

public Bitmap Crop(Bitmap bmp)
{
  int w = bmp.Width, h = bmp.Height;

  Func allWhiteRow = row =>
  {
    for (int i = 0; i < w; ++i)
      if (bmp.GetPixel(i, row).R != 255)
        return false;
    return true;
  };

  Func allWhiteColumn = col =>
  {
    for (int i = 0; i < h; ++i)
      if (bmp.GetPixel(col, i).R != 255)
        return false;
    return true;
  };

  int topmost = 0;
  for (int row = 0; row < h; ++row)
  {
    if (allWhiteRow(row))
      topmost = row;
    else break;
  }

  int bottommost = 0;
  for (int row = h - 1; row >= 0; --row)
  {
    if (allWhiteRow(row))
      bottommost = row;
    else break;
  }

  int leftmost = 0, rightmost = 0;
  for (int col = 0; col < w; ++col)
  {
    if (allWhiteColumn(col))
      leftmost = col;
    else
      break;
  }

  for (int col = w-1; col >= 0; --col)
  {
    if (allWhiteColumn(col))
      rightmost = col;
    else
      break;
  }

  int croppedWidth = rightmost - leftmost;
  int croppedHeight = bottommost - topmost;
  try
  {
    Bitmap target = new Bitmap(croppedWidth, croppedHeight);
    using (Graphics g = Graphics.FromImage(target))
    {
      g.DrawImage(bmp,
        new RectangleF(0, 0, croppedWidth, croppedHeight),
        new RectangleF(leftmost, topmost, croppedWidth, croppedHeight),
        GraphicsUnit.Pixel);
    }
    return target;
  }
  catch (Exception ex)
  {
    throw new Exception(
      string.Format("Values are topmost={0} btm={1} left={2} right={3}", topmost, bottommost, leftmost, rightmost),
      ex);
  }
}