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

  Func<int, bool> 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);
  }
}

Answer 2

fix remaining 1px white space at the top and left

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

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

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

        int leftMost = 0;
        for (int col = 0; col < w; col++)
        {
            if (IsAllWhiteColumn(col)) leftMost = col + 1;
            else break;
        }

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

        int topMost = 0;
        for (int row = 0; row < h; row++)
        {
            if (IsAllWhiteRow(row)) topMost = row + 1;
            else break;
        }

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

        if (rightMost == 0 && bottomMost == 0 && leftMost == w && topMost == h)
        {
            return bitmap;
        }

        int croppedWidth = rightMost - leftMost + 1;
        int croppedHeight = bottomMost - topMost + 1;

        try
        {
            Bitmap target = new Bitmap(croppedWidth, croppedHeight);
            using (Graphics g = Graphics.FromImage(target))
            {
                g.DrawImage(bitmap,
                    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 top={0} bottom={1} left={2} right={3}", topMost, bottomMost, leftMost, rightMost), ex);
        }
    }