使用c#，合并多个bitMap图像

当只需要两个图像合并的时候，可以简单的使用gdi+，把两个图像画到一个画布上面实现合并bitmap.

当需要将许多bitmap合并时，由于bitmap类限制，长度或宽度太大时会报异常，前面这种方法就行不通了。

由于bitmapp属于位图格式，了解图像格式后，发现，bitmap文件的第3-8位存储了文件大小信息，第19-22位存储了高度信息，第23-26位存储了宽度信息。文件头后面都是像素的argb，并无其它信息。于是，试想一下，如果把第二张图像的像素argb放到第一张后面，并修改第一张的文件头信息，是不是就可以实现文件合并了呢。事实证明：yes。

下面就看看代码：

//设置文件头里面文件大小信息

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);}}}

设置文件头里面文件长度和宽度信息

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);}}}}

合并多个bitmap文件,并生成一个最终文件

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 memoryBitmapData 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 memorybmp.UnlockBits(bmpdata);}
catch{
return null;}
return bits;}

完成喽。

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