The array version

gistfile1.cs

public Boundaries CheckBoundaries(int[] pixels) {
            // check left
            double boundayFactor = 0.1; //10% of the image width/height
            Boundaries b = new Boundaries();
            b.Left = CheckLeft(pixels, boundayFactor);
            b.Right = CheckRight(pixels, boundayFactor);
            b.Top = CheckTop(pixels, boundayFactor);
            b.Bottom = CheckBottom(pixels, boundayFactor);
            return b;
        }

        private bool CheckLeft(int[] bmp, double bf)
        {
            for (int i = 0; i < (int)(this.width*bf); i++)
            {
                int count = 0;
                for (int j = 0; j < this.height-1; j++)
                {
                    if (GetPixel(bmp,i, j) != 0)
                    {
                        count++;
                    }
                }
                if (count > 12)
                    return true;
            }
            return false;
        }

        private bool CheckRight(int[] bmp, double bf)
        {
            for (int i = this.width-1; i > (int)(this.width * (1-bf)); i--)
            {
                int count = 0;
                for (int j = 0; j < this.height-1; j++)
                {
                    if (GetPixel(bmp,j, i) != 0)
                    {
                        count++;
                    }
                }
                if (count > 12)
                    return true;
            }
            return false;
        }

        private bool CheckTop(int[] bmp, double bf)
        {
            for (int i = 0; i < (int) (this.height*bf); i++)
            {
                int count = 0;
                for (int j = 0; j < this.width-1; j++)
                {
                    if (GetPixel(bmp,j, i) != 0)
                    {
                        count++;
                    }
                }
                if (count > 12)
                    return true;
            }
            return false;
        }

        private bool CheckBottom(int[] bmp, double bf)
        {
            for (int i = this.height - 1; i > (int)(this.height * (1 - bf)); i--)
            {
                int count = 0;
                for (int j = 0; j < this.width-1; j++)
                {
                    if (GetPixel(bmp,j, i) != 0)
                    {
                        count++;
                    }
                }
                if (count > 12)
                    return true;
            }
            return false;
        }

        private int GetPixel(int[] pixels, int i, int j)
        {
            return pixels[((this.width-1) * i) + j];
        }
        
        public class Boundaries {
            public bool Left { get; set; }
            public bool Right { get; set; }
            public bool Top { get; set; }
            public bool Bottom { get; set; }
        }