跟据9png的实现原理自己写了个生成图片的函数，9png的原理是将图片切成9块如下
其中1、3、7、9不进行缩放，2,4，5，6，8进行缩放，这样就防止了放大后导致边界出现锯齿的问题
在实现过程中主要的就是找到4个关键点，如下
然后根据p1,p2,p3,p4将原图画到新大小的图上
具体代码如下
获得关键点
代码语言：javascript复制/// <summary>
/// 获取4个关键坐标点左边1,2 上边1,2
/// </summary>
/// <param name="bitmap">图片</param>
/// <param name="backColor">背景色</param>
/// <param name="intAalpha">透明度</param>
/// <returns>0：左1 1：左2 2：上1 3：上2</returns>
private Point[] GetIndex(Bitmap bitmap, Color? backColor = null, int intAalpha = 0)
{
int intTop = 0;
int intRight = 0;
int intBottom = 0;
int intLeft = 0;
Point ptop1 = Point.Empty, ptop2 = Point.Empty;
Point pleft1 = Point.Empty, pleft2 = Point.Empty;
Point pbottom1 = Point.Empty, pbottom2 = Point.Empty;
Point pright1 = Point.Empty, pright2 = Point.Empty;
#region 边界
//left
for (int x = 0; x < bitmap.Width; x )
{
for (int y = 0; y < bitmap.Height; y )
{
Color c = bitmap.GetPixel(x, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
intLeft = x;
x = int.MaxValue - 10;
break;
}
}
//right
for (int x = bitmap.Width - 1; x >= 0; x--)
{
for (int y = 0; y < bitmap.Height; y )
{
Color c = bitmap.GetPixel(x, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
intRight = x;
x = -10;
break;
}
}
//top
for (int y = 0; y < bitmap.Height; y )
{
for (int x = 0; x < bitmap.Width; x )
{
Color c = bitmap.GetPixel(x, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
intTop = y;
y = int.MaxValue - 10;
break;
}
}
//bottom
for (int y = bitmap.Height - 1; y >= 0; y--)
{
for (int x = 0; x < bitmap.Width; x )
{
Color c = bitmap.GetPixel(x, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
intBottom = y;
y = -10;
break;
}
}
#endregion
#region 顶点
bool blnGet1 = false;
bool blnGet2 = false;
//上1 下1
for (int x = 0; x < bitmap.Width; x )
{
//上1
if (!blnGet1)
{
Color c = bitmap.GetPixel(x, intTop);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
ptop1 = new Point(x, intTop);
blnGet1 = true;
}
//下1
if (!blnGet2)
{
Color c = bitmap.GetPixel(x, intBottom);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
pbottom1 = new Point(x, intBottom);
blnGet2 = true;
}
if (blnGet1 && blnGet2)
{
break;
}
}
blnGet1 = false;
blnGet2 = false;
//上2 下2
for (int x = bitmap.Width - 1; x >= 0; x--)
{
//上2
if (!blnGet1)
{
Color c = bitmap.GetPixel(x, intTop);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
ptop2 = new Point(x, intTop);
blnGet1 = true;
}
//下2
if (!blnGet2)
{
Color c = bitmap.GetPixel(x, intBottom);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
pbottom2 = new Point(x, intBottom);
blnGet2 = true;
}
if (blnGet1 && blnGet2)
{
break;
}
}
blnGet1 = false;
blnGet2 = false;
//左1 右1
for (int y = 0; y < bitmap.Height; y )
{
//左1
if (!blnGet1)
{
Color c = bitmap.GetPixel(intLeft, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
pleft1 = new Point(intLeft, y);
blnGet1 = true;
}
//右1
if (!blnGet2)
{
Color c = bitmap.GetPixel(intRight, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
pright1 = new Point(intRight, y);
blnGet2 = true;
}
if (blnGet1 && blnGet2)
{
break;
}
}
blnGet1 = false;
blnGet2 = false;
//左2 右2
for (int y = bitmap.Height - 1; y >= 0; y--)
{
//左2
if (!blnGet1)
{
Color c = bitmap.GetPixel(intLeft, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
pleft2 = new Point(intLeft, y);
blnGet1 = true;
}
//右2
if (!blnGet2)
{
Color c = bitmap.GetPixel(intRight, y);
if (c.A <= intAalpha)
continue;
if (backColor.HasValue && c.ToArgb() == backColor.Value.ToArgb())
{
continue;
}
pright2 = new Point(intRight, y);
blnGet2 = true;
}
if (blnGet1 && blnGet2)
{
break;
}
}
#endregion
Point pRleft1, pRleft2;
Point pRtop1, pRtop2;
int intLeftMax = Math.Max(ptop1.X, pbottom1.X);
int intRightMin = Math.Min(ptop2.X, pbottom2.X);
int intTopMax = Math.Max(pleft1.Y, pright1.Y);
int intBottomMin = Math.Min(pleft2.Y, pright2.Y);
if (intRightMin - intLeftMax ==0)
{
intRightMin = intRightMin 1;
}
else if (intRightMin - intLeftMax > 4)
{
intRightMin = intRightMin - 2;
intLeftMax = intLeftMax 2;
}
if (intBottomMin - intTopMax == 0)
{
intBottomMin = intBottomMin 1;
}
else if (intBottomMin - intTopMax > 4)
{
intBottomMin = intBottomMin - 2;
intTopMax = intTopMax 2;
}
pRleft1 = new Point(intLeft, intTopMax);
pRleft2 = new Point(intLeft, intBottomMin);
pRtop1 = new Point(intLeftMax, intTop);
pRtop2 = new Point(intRightMin, intTop);
Point[] ps = new Point[4];
ps[0] = pRleft1;
ps[1] = pRleft2;
ps[2] = pRtop1;
ps[3] = ptop2;
return ps;
}画图
代码语言：javascript复制 private Bitmap CreateBitmap(Bitmap bitmap, Point[] ps, Size size)
{
Bitmap _returnBitmap = new Bitmap(size.Width, size.Height);
Graphics g = Graphics.FromImage(_returnBitmap);
//左上角
Rectangle destRect = new Rectangle(new Point(0, 0), new Size(ps[2].X, ps[0].Y));
g.DrawImage(bitmap, destRect, 0, 0, ps[2].X, ps[0].Y, GraphicsUnit.Pixel);
//右上角
destRect = new Rectangle(new Point(size.Width - (bitmap.Width - ps[3].X), ps[3].Y), new Size(bitmap.Width - ps[3].X, ps[0].Y));
g.DrawImage(bitmap, destRect, ps[3].X, ps[3].Y, bitmap.Width - ps[3].X, ps[0].Y, GraphicsUnit.Pixel);
//左下角
destRect = new Rectangle(new Point(0, size.Height - (bitmap.Height - ps[1].Y)), new Size(ps[2].X, bitmap.Height - ps[1].Y));
g.DrawImage(bitmap, destRect, 0, ps[1].Y, ps[2].X, (bitmap.Height - ps[1].Y), GraphicsUnit.Pixel);
//右下角
destRect = new Rectangle(new Point(size.Width - (bitmap.Width - ps[3].X), size.Height - (bitmap.Height - ps[1].Y)), new Size(bitmap.Width - ps[3].X, bitmap.Height - ps[1].Y));
g.DrawImage(bitmap, destRect, ps[3].X, ps[1].Y, bitmap.Width - ps[3].X, bitmap.Height - ps[1].Y, GraphicsUnit.Pixel);
//上中
destRect = new Rectangle(new Point(ps[2].X, 0), new Size(size.Width - ps[2].X - (bitmap.Width - ps[3].X), ps[0].Y));
g.DrawImage(bitmap, destRect, ps[2].X, 0, ps[3].X - ps[2].X, ps[0].Y, GraphicsUnit.Pixel);
//下中
destRect = new Rectangle(new Point(ps[2].X, size.Height - (bitmap.Height - ps[1].Y)), new Size(size.Width - ps[2].X - (bitmap.Width - ps[3].X), bitmap.Height - ps[1].Y));
g.DrawImage(bitmap, destRect, ps[2].X, ps[1].Y, ps[3].X - ps[2].X, bitmap.Height - ps[1].Y, GraphicsUnit.Pixel);
//左中
destRect = new Rectangle(new Point(0, ps[0].Y), new Size(ps[2].X, size.Height - ps[0].Y - (bitmap.Height - ps[1].Y)));
g.DrawImage(bitmap, destRect, 0, ps[0].Y, ps[2].X, ps[1].Y-ps[0].Y, GraphicsUnit.Pixel);
//右中
destRect = new Rectangle(new Point(size.Width - (bitmap.Width - ps[3].X), ps[0].Y), new Size(bitmap.Width - ps[3].X, size.Height - ps[0].Y - (bitmap.Height - ps[1].Y)));
g.DrawImage(bitmap, destRect, ps[3].X, ps[0].Y, bitmap.Width-ps[3].X, ps[1].Y - ps[0].Y, GraphicsUnit.Pixel);
//中中
destRect = new Rectangle(new Point(ps[2].X, ps[0].Y), new Size(size.Width - ps[2].X - (bitmap.Width - ps[3].X), size.Height - ps[0].Y - (bitmap.Height - ps[1].Y)));
g.DrawImage(bitmap, destRect, ps[2].X, ps[0].Y, ps[3].X - ps[2].X, ps[1].Y - ps[0].Y, GraphicsUnit.Pixel);
g.Dispose();
return _returnBitmap;
}使用
代码语言：javascript复制 string strPath = @"D:work-hzhcodecy_hcmzc_v10Km.PosZCKm.PosZCResourcesinternet .png";
Bitmap bitmap = new Bitmap(strPath);
Point[] ps = GetIndex(bitmap,Color.White);
Bitmap br = CreateBitmap(bitmap, ps, new Size(400, 400));
br.Save("d:\123.png");测试原图（100*100）
放大后（400*400）
这个是随便找的图，一般在应用中，是纯色活渐变色的会比较好，中间有图案的话 效果就不是太好了
