C # BitMap combined image, generating large bitmap

Using c #, merging multiple images bitMap

When only two images combined, you can simply use GDI +, draw the two images to achieve a combined top canvas bitmap.

When it is desired to merge a number of bitmap, bitmap-based limitations because, when the length or width is too large will be reported anomaly, this method will not work front.

Since bitmapp belonging bitmap format, an image format after understanding found, the bitmap file 3-8 stores the file size information, bits 19-22 of the altitude information is stored, width 23-26 bits stored information. Following the header is the pixel argb, no other information. So, imagine if the second pixel of the image argb back into the first, and the first modification of the file header information, you can achieve file is not merged yet. Facts have proved that: yes.

// set the file header information inside the file size

public void SetBitmapFileSizeInfo(string filePath)
        {
            FileInfo fileInfo = new FileInfo(filePath);
            long le = fileInfo.Length;
            string hexSize = le.ToString("X").PadLeft(8, '0');
            int size1 = Convert.ToInt32(hexSize.Substring(0, 2), 16);
            int size2 = Convert.ToInt32(hexSize.Substring(2, 2), 16);
            int size3 = Convert.ToInt32(hexSize.Substring(4, 2), 16);
            int size4 = Convert.ToInt32(hexSize.Substring(6, 2), 16);
            byte[] sizeBytes = new byte[] { (byte)size4, (byte)size3, (byte)size2, (byte)size1 };
            using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Write))
            {
                using (BinaryWriter r = new BinaryWriter(fs))
                {
                    r.Seek(2, 0);
                    r.Write(sizeBytes, 0, sizeBytes.Length);
                }
            }
        }

Set inside the header length and width information files

 public void SetBitmapSizeInfo(string filePath,int width=0,int height=0)
        {
            if (height != 0)
            {
                string hexHeight = height.ToString("X").PadLeft(8, '0');
                int h1 = Convert.ToInt32(hexHeight.Substring(0, 2), 16);
                int h2 = Convert.ToInt32(hexHeight.Substring(2, 2), 16);
                int h3 = Convert.ToInt32(hexHeight.Substring(4, 2), 16);
                int h4 = Convert.ToInt32(hexHeight.Substring(6, 2), 16);
                byte[] sizeHeight = new byte[] { (byte)h4, (byte)h3, (byte)h2, (byte)h1 };
                using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.ReadWrite))
                {
                    using (BinaryWriter r = new BinaryWriter(fs))
                    {
                        r.Seek(22, 0);//高度保存位置
                        r.Write(sizeHeight, 0, sizeHeight.Length);
                    }
                }
            }
            if (width != 0)
            {
                string hexWidth = height.ToString("X").PadLeft(8, '0');
                int w1 = Convert.ToInt32(hexWidth.Substring(0, 2), 16);
                int w2 = Convert.ToInt32(hexWidth.Substring(2, 2), 16);
                int w3 = Convert.ToInt32(hexWidth.Substring(4, 2), 16);
                int w4 = Convert.ToInt32(hexWidth.Substring(6, 2), 16);
                byte[] sizeWidth = new byte[] { (byte)w4, (byte)w3, (byte)w2, (byte)w1 };
                using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.ReadWrite))
                {
                    using (BinaryWriter r = new BinaryWriter(fs))
                    {
                        r.Seek(18, 0);//高度保存位置
                        r.Write(sizeWidth, 0, sizeWidth.Length);
                    }
                }
            }
        }

Combine multiple bitmap files, and generate a final document

private void CreateBitMap(string tempPath,string imagePath)
        {
            string[] files = Directory.GetFiles(tempPath, "*.png");
            Bitmap bmp;
            int height=0;
            for (int i = files.Length-1; i >0; i--)
            {
                string fileName = files[i];
                bmp = new Bitmap(fileName);
                if (i == files.Length - 1)
                {
                    bmp.Save(imagePath, ImageFormat.Bmp);
                    height += bmp.Height;
                    bmp.Dispose();
                    continue;
                }
                else
                {
                    byte[] bytes = GetImageRasterBytes(bmp, PixelFormat.Format32bppRgb);
                    using (FileStream fs = new FileStream(imagePath, FileMode.Open, FileAccess.Write))
                    {
                        fs.Seek(fs.Length, 0);
                        fs.Write(bytes, 0, bytes.Length);
                    }
                    height += bmp.Height;
                    bmp.Dispose();
                }
            }
            SetBitmapFileSizeInfo(imagePath);
            SetBitmapSizeInfo(imagePath, height: height);
            //MessageBox.Show("合并成功");
        }
         private static byte[] GetImageRasterBytes(Bitmap bmp, PixelFormat format)
        {
            Rectangle rect = new Rectangle(0, 0, bmp.Width, bmp.Height);
            byte[] bits = null;
            try
            {
                // Lock the managed memory
                BitmapData bmpdata = bmp.LockBits(rect, ImageLockMode.ReadWrite, format);
                // Declare an array to hold the bytes of the bitmap.
                bits = new byte[bmpdata.Stride * bmpdata.Height];
                // Copy the values into the array.
                System.Runtime.InteropServices.Marshal.Copy(bmpdata.Scan0, bits, 0, bits.Length);
                // Release managed memory
                bmp.UnlockBits(bmpdata);
            }
            catch
            {
                return null;
            }
            return bits;
        }