实例图片：
实例代码：
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Net;
namespace Micro.Common
{
/// <summary>
/// 多张图片合成九宫格
/// string[] path = new string[4];
/// path[0] = "X:\\1.jpg";
/// path[1] = "X:\\2.jpg";
/// path[2] = "X:\\3.jpg";
/// path[3] = "X:\\4.jpg";
/// AvatarHelper jiuGong = new AvatarHelper();
/// var base64 = jiuGong.SyntheticToBase64(path);
/// </summary>
public partial class AvatarHelper
{
private const int _width = 132; //合成九宫图的宽度
private const int _height = 132; //合成九宫图的高度
/// <summary>
/// 获取坐标
/// </summary>
/// <param name="number">数量</param>
/// <returns></returns>
private string[] GetXy(int number)
{
string[] s = new string[number];
int _x = 0;
int _y = 0;
switch (number)
{
case 1:
_x = _y = 6;
s[0] = "6,6";
break;
case 2:
_x = _y = 4;
s[0] = "4," + (132 / 2 - 60 / 2);
s[1] = 60 + 2 * _x + "," + (132 / 2 - 60 / 2);
break;
case 3:
_x = _y = 4;
s[0] = (132 / 2 - 60 / 2) + "," + _y;
s[1] = _x + "," + (60 + 2 * _y);
s[2] = (60 + 2 * _y) + "," + (60 + 2 * _y);
break;
case 4:
_x = _y = 4;
s[0] = _x + "," + _y;
s[1] = (_x * 2 + 60) + "," + _y;
s[2] = _x + "," + (60 + 2 * _y);
s[3] = (60 + 2 * _y) + "," + (60 + 2 * _y);
break;
case 5:
_x = _y = 3;
s[0] = (132 - 40 * 2 - _x) / 2 + "," + (132 - 40 * 2 - _y) / 2;
s[1] = ((132 - 40 * 2 - _x) / 2 + 40 + _x) + "," + (132 - 40 * 2 - _y) / 2;
s[2] = _x + "," + ((132 - 40 * 2 - _x) / 2 + 40 + _y);
s[3] = (_x * 2 + 40) + "," + ((132 - 40 * 2 - _x) / 2 + 40 + _y);
s[4] = (_x * 3 + 40 * 2) + "," + ((132 - 40 * 2 - _x) / 2 + 40 + _y);
break;
case 6:
_x = _y = 3;
s[0] = _x + "," + ((132 - 40 * 2 - _x) / 2);
s[1] = (_x * 2 + 40) + "," + ((132 - 40 * 2 - _x) / 2);
s[2] = (_x * 3 + 40 * 2) + "," + ((132 - 40 * 2 - _x) / 2);
s[3] = _x + "," + ((132 - 40 * 2 - _x) / 2 + 40 + _y);
s[4] = (_x * 2 + 40) + "," + ((132 - 40 * 2 - _x) / 2 + 40 + _y);
s[5] = (_x * 3 + 40 * 2) + "," + ((132 - 40 * 2 - _x) / 2 + 40 + _y);
break;
case 7:
_x = _y = 3;
s[0] = (132 - 40) / 2 + "," + _y;
s[1] = _x + "," + (_y * 2 + 40);
s[2] = (_x * 2 + 40) + "," + (_y * 2 + 40);
s[3] = (_x * 3 + 40 * 2) + "," + (_y * 2 + 40);
s[4] = _x + "," + (_y * 3 + 40 * 2);
s[5] = (_x * 2 + 40) + "," + (_y * 3 + 40 * 2);
s[6] = (_x * 3 + 40 * 2) + "," + (_y * 3 + 40 * 2);
break;
case 8:
_x = _y = 3;
s[0] = (132 - 80 - _x) / 2 + "," + _y;
s[1] = ((132 - 80 - _x) / 2 + _x + 40) + "," + _y;
s[2] = _x + "," + (_y * 2 + 40);
s[3] = (_x * 2 + 40) + "," + (_y * 2 + 40);
s[4] = (_x * 3 + 40 * 2) + "," + (_y * 2 + 40);
s[5] = _x + "," + (_y * 3 + 40 * 2);
s[6] = (_x * 2 + 40) + "," + (_y * 3 + 40 * 2);
s[7] = (_x * 3 + 40 * 2) + "," + (_y * 3 + 40 * 2);
break;
case 9:
_x = _y = 3;
s[0] = _x + "," + _y;
s[1] = _x * 2 + 40 + "," + _y;
s[2] = _x * 3 + 40 * 2 + "," + _y;
s[3] = _x + "," + (_y * 2 + 40);
s[4] = (_x * 2 + 40) + "," + (_y * 2 + 40);
s[5] = (_x * 3 + 40 * 2) + "," + (_y * 2 + 40);
s[6] = _x + "," + (_y * 3 + 40 * 2);
s[7] = (_x * 2 + 40) + "," + (_y * 3 + 40 * 2);
s[8] = (_x * 3 + 40 * 2) + "," + (_y * 3 + 40 * 2);
break;
}
return s;
}
/// <summary>
/// 获取尺寸
/// </summary>
/// <param name="number">数量</param>
/// <returns></returns>
private float GetSize(int number)
{
int w = 0;
if (number == 1)
{
w = 120;
}
if (number > 1 && number <= 4)
{
w = 60;
}
if (number >= 5)
{
w = 40;
}
return w;
}
/// <summary>
/// 图片压缩
/// </summary>
/// <param name="bitmap">Bitmap</param>
/// <param name="width">宽</param>
/// <param name="height">高</param>
/// <returns></returns>
private Bitmap ImageCompression(Bitmap bitmap, int width, int height)
{
using (var bmp = new Bitmap(width, height))
{
//从Bitmap创建一个Graphics对象，用来绘制高质量的缩小图。
using (var gr = Graphics.FromImage(bmp))
{
//设置 System.Drawing.Graphics对象的SmoothingMode属性为HighQuality
gr.SmoothingMode = SmoothingMode.HighQuality;
//下面这个也设成高质量
gr.CompositingQuality = CompositingQuality.HighQuality;
//下面这个设成High
gr.InterpolationMode = InterpolationMode.High;
//把原始图像绘制成上面所设置宽高的截取图
var rectDestination = new Rectangle(0, 0, width, height);
//绘制
gr.DrawImage(bitmap, 0, 0, rectDestination, GraphicsUnit.Pixel);
//保存截取的图片
return bitmap;
}
}
}
/// <summary>
/// 下载图片
/// </summary>
/// <param name="path">路径</param>
/// <returns></returns>
private Bitmap PathConvertBitmap(string path, bool isHttp)
{
if (!isHttp)
{
return new Bitmap(path);
}
using (WebClient client = new WebClient())
{
using (Stream stream = client.OpenRead(path))
{
return (Bitmap)Image.FromStream(stream);
}
}
}
/// <summary>
/// 合成九宫图
/// </summary>
/// <param name="imgPath">图片路径(绝对路径)</param>
/// <param name="isHttp">网络图片</param>
/// <returns></returns>
public Bitmap Synthetic(string[] imgPath, bool isHttp = false)
{
//合成数量
int number = imgPath.Length;
//坐标
string[] xys = this.GetXy(number);
//尺寸
var size = this.GetSize(number);
Bitmap backgroudBitmap = new Bitmap(_width, _height);
using (Graphics g = Graphics.FromImage(backgroudBitmap))
{
//设置 System.Drawing.Graphics对象的SmoothingMode属性为HighQuality
g.SmoothingMode = SmoothingMode.HighQuality;
//下面这个也设成高质量
g.CompositingQuality = CompositingQuality.HighQuality;
//下面这个设成High
g.InterpolationMode = InterpolationMode.High;
//清除画布,背景设置为透明色
g.Clear(Color.FromArgb(255, 255, 255));
for (int i = 0; i < imgPath.Length; i++)
{
var bitmap = this.PathConvertBitmap(imgPath[i], isHttp);
string[] xy = xys[i].Split(',');
int x = int.Parse(xy[0]);
int y = int.Parse(xy[1]);
bitmap = this.ImageCompression(bitmap, x, y);
g.DrawImage(bitmap, x, y, size, size);
bitmap.Dispose();
}
}
return backgroudBitmap;
}
/// <summary>
/// Bitmap转Base64字符串
/// </summary>
/// <param name="imgPath">图片路径(绝对路径)</param>
/// <param name="isHttp">网络图片</param>
/// <returns></returns>
public string SyntheticToBase64(string[] imgPath, bool isHttp = false)
{
Bitmap bmp = Synthetic(imgPath, isHttp);
MemoryStream ms = new MemoryStream();
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
byte[] arr = new byte[ms.Length];
ms.Position = 0;
ms.Read(arr, 0, (int)ms.Length);
ms.Close();
String strbaser64 = Convert.ToBase64String(arr);
return $"data:image/jpeg;base64,{strbaser64}";
}
}
}
参考：https://blog.csdn.net/qq_44838095/article/details/121829267