Asp.Net生成BMP图像
利用以下代码可以生成一组随机的数字图片，可用于验证码。。
// 在此处放置用户代码以初始化页面
Bitmap newBitmap = new Bitmap(36,16,PixelFormat.Format24bppRgb);
//根据上面创建的位图对象创建绘图面
Graphics g = Graphics.FromImage(newBitmap);
g.Clear(Color.White);
//创建字体对象
Font textFont = new Font("Times New Roman",10);
//创建RectangleF结构指定一个区域
RectangleF rectangle = new RectangleF(0,0,36,16);
//创建随机数对象
Random rd = new Random();
//取得随机数
int valationNo = 1000 + rd.Next(8999);
for(int i=0; i<50; i++)
{
int x = rd.Next(newBitmap.Width);
int y = rd.Next(newBitmap.Height);
newBitmap.SetPixel(x, y, Color.Gray);
}
//在上面填充的矩形区域中填充上面生成的随机数
g.DrawString(valationNo.ToString(), textFont, new SolidBrush(Color.Black), rectangle);
//把创建的位图保存到指定的路径
newBitmap.Save("d:\\pic\\Img3.bmp", ImageFormat.Bmp);
Bitmap newBitmap = new Bitmap(36,16,PixelFormat.Format8bppIndexed);
//根据上面创建的位图对象创建绘图面
Graphics g = Graphics.FromImage(newBitmap);
g.Clear(Color.White);
//创建字体对象
Font textFont = new Font("Times New Roman",10);
//创建RectangleF结构指定一个区域
RectangleF rectangle = new RectangleF(0,0,36,16);
//创建随机数对象
Random rd = new Random();
//取得随机数
int valationNo = 1000 + rd.Next(8999);
for(int i=0; i<50; i++)
{
int x = rd.Next(newBitmap.Width);
int y = rd.Next(newBitmap.Height);
newBitmap.SetPixel(x, y, Color.Gray);
}
//在上面填充的矩形区域中填充上面生成的随机数
g.DrawString(valationNo.ToString(), textFont, new SolidBrush(Color.Black), rectangle);
//把创建的位图保存到指定的路径
newBitmap.Save("d:\\pic\\Img3.bmp", ImageFormat.Bmp);
异常详细信息: System.Exception: 无法从带有索引像素格式的图像创建 Graphics 对象。
源错误:
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
报如上错误，且SetPixel方法也不能用了。
找了半天也没找到解决方法。既然此路不通那就换条路走咯，于是乎找到了一个很好的图片格式转换工具
Graphics Converter Pro for Vector，功能十分强大啊，按最开始的方法生成了9000张图片，然后转换成WBMP
总算是OK了。。。。。
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
其他一些图像处理方法
反相
public static bool Invert(Bitmap b)
{
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height),
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
System.IntPtr Scan0 = bmData.Scan0;
unsafe
{
byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;
int nWidth = b.Width * 3;
for(int y=0;y < b.Height;++y)
{
for(int x=0; x < nWidth; ++x
{
p[0] = (byte)(255-p[0]);
++p;
}
p += nOffset;
}
}
b.UnlockBits(bmData);
return true;
}
public static bool Grayscale(Bitmap b)
{
//变成黑白
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height),
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
System.IntPtr Scan0 = bmData.Scan0;
unsafe
{
byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;
byte red, green, blue;
for(int y=0;y < b.Height;++y)
{
for(int x=0; x < b.Width; ++x
{
blue = p[0];
green = p[1];
red = p[2];
p[0] = p[1] = p[2] = (byte)(.299 * red
+ .587 * green
+ .114 * blue);
p += 3;
}
p += nOffset;
}
}
b.UnlockBits(bmData);
return true;
}
亮度
public static bool Brightness(Bitmap b,int nBrightness)
{
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height),
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
System.IntPtr Scan0 = bmData.Scan0;
unsafe
{
byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;
int nWidth = b.Width * 3;
for(int y=0;y<b.Height;++y)
{
for (int x = 0; x < nWidth; ++x)
{
int nVal = (int) (p[0] + nBrightness);
if (nVal < 0) nVal = 0;
if (nVal > 255) nVal = 255;
p[0] = (byte)nVal;
++p;
}
p += nOffset;
}
}
b.UnlockBits(bmData);
return true;
}
对比度
public static bool Contrast(Bitmap b,int nContrast)
{
if (nContrast < -100) return false;
if (nContrast > 100) return false;
double pixel = 0, contrast = (100.0+nContrast)/100.0;
contrast *= contrast;
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height),
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
System.IntPtr Scan0 = bmData.Scan0;
unsafe
{
byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;
int nWidth = b.Width * 3;
for(int y=0;y<b.Height;++y)
{
for (int x = 0; x < nWidth;++x)
{
byte color = p[0];
pixel = color/255.0;
pixel -= 0.5;
pixel *= contrast;
pixel += 0.5;
pixel *= 255;
if (pixel < 0) pixel = 0;
if (pixel > 255) pixel = 255;
p[0] = (byte) pixel;
++p;
}
p += nOffset;
}
}
b.UnlockBits(bmData);
return true;
}
public static bool Gamma(Bitmap b)
{
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height),
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
System.IntPtr Scan0 = bmData.Scan0;
byte [] redGamma = new byte [256];
byte [] greenGamma = new byte [256];
byte [] blueGamma = new byte [256];
for (int i = 0; i < 256; ++i)
{
redGamma[i] = (byte)Math.Min(255, (int)(( 255.0
* Math.Pow(i/255.0, 1.0/5)) + 0.5));//其中1.0/5里的5是红色Gamma值。
greenGamma[i] = (byte)Math.Min(255, (int)(( 255.0
* Math.Pow(i/255.0, 1.0/5)) + 0.5));
blueGamma[i] = (byte)Math.Min(255, (int)(( 255.0
* Math.Pow(i/255.0, 1.0/5)) + 0.5));
}
unsafe
{
byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;
int nWidth = b.Width * 3;
byte red, green, blue;
for(int y=0;y<b.Height;++y)
{
for (int x = 0; x < b.Width;++x)
{
blue = p[0];
green = p[1];
red = p[2];
p[0]=(byte)blueGamma[(int)blue];
p[1]=(byte)greenGamma[(int)green];
p[2]=(byte)redGamma[(int)red];
p+=3;
}
p += nOffset;
}
}
b.UnlockBits(bmData);
return true;
}
通道
public static bool Channel(Bitmap b,char rgb)
{
BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height),
ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb);
int stride = bmData.Stride;
System.IntPtr Scan0 = bmData.Scan0;
unsafe
{
byte * p = (byte *)(void *)Scan0;
int nOffset = stride - b.Width*3;
int nWidth = b.Width * 3;
byte red, green, blue;
for(int y=0;y<b.Height;++y)
{
for (int x = 0; x < b.Width;++x)
{
switch(rgb)
{
case 'r':
p[0]=(byte)0;
p[1]=(byte)0;
break;
case 'g':
p[0]=(byte)0;
p[2]=(byte)0;
break;
case 'b':
p[2]=(byte)0;
p[1]=(byte)0;
break;
}
p+=3;
}
p += nOffset;
}
}
b.UnlockBits(bmData);
return true;
}
--------------------------------------------------------------------------------------------------------
附：对 ASP.NET 图像的颜色量化(Quantization)进行优化
http://www.microsoft.com/china/MSDN/library/archives/library/DNAspp/html/colorquant.asp
利用以下代码可以生成一组随机的数字图片，可用于验证码。。
// 在此处放置用户代码以初始化页面 Bitmap newBitmap = new Bitmap(36,16,PixelFormat.Format24bppRgb); //根据上面创建的位图对象创建绘图面 Graphics g = Graphics.FromImage(newBitmap); g.Clear(Color.White); //创建字体对象 Font textFont = new Font("Times New Roman",10); //创建RectangleF结构指定一个区域 RectangleF rectangle = new RectangleF(0,0,36,16); //创建随机数对象 Random rd = new Random(); //取得随机数 int valationNo = 1000 + rd.Next(8999); for(int i=0; i<50; i++) {
int x = rd.Next(newBitmap.Width); int y = rd.Next(newBitmap.Height); newBitmap.SetPixel(x, y, Color.Gray); } //在上面填充的矩形区域中填充上面生成的随机数 g.DrawString(valationNo.ToString(), textFont, new SolidBrush(Color.Black), rectangle); //把创建的位图保存到指定的路径 newBitmap.Save("d:\\pic\\Img3.bmp", ImageFormat.Bmp);但是早先的Wap中只支持256色的WBMP的图片格式，于是修改代码
Bitmap newBitmap = new Bitmap(36,16,PixelFormat.Format8bppIndexed); //根据上面创建的位图对象创建绘图面 Graphics g = Graphics.FromImage(newBitmap); g.Clear(Color.White); //创建字体对象 Font textFont = new Font("Times New Roman",10); //创建RectangleF结构指定一个区域 RectangleF rectangle = new RectangleF(0,0,36,16); //创建随机数对象 Random rd = new Random(); //取得随机数 int valationNo = 1000 + rd.Next(8999); for(int i=0; i<50; i++) { int x = rd.Next(newBitmap.Width); int y = rd.Next(newBitmap.Height); newBitmap.SetPixel(x, y, Color.Gray); } //在上面填充的矩形区域中填充上面生成的随机数 g.DrawString(valationNo.ToString(), textFont, new SolidBrush(Color.Black), rectangle); //把创建的位图保存到指定的路径 newBitmap.Save("d:\\pic\\Img3.bmp", ImageFormat.Bmp);无法从带有索引像素格式的图像创建 Graphics 对象。
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。异常详细信息: System.Exception: 无法从带有索引像素格式的图像创建 Graphics 对象。
源错误:
|
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
报如上错误，且SetPixel方法也不能用了。
找了半天也没找到解决方法。既然此路不通那就换条路走咯，于是乎找到了一个很好的图片格式转换工具
Graphics Converter Pro for Vector，功能十分强大啊，按最开始的方法生成了9000张图片，然后转换成WBMP
总算是OK了。。。。。
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
其他一些图像处理方法
反相public static bool Invert(Bitmap b){ BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { 
byte * p = (byte *)(void *)Scan0;int nOffset = stride - b.Width*3; int nWidth = b.Width * 3;for(int y=0;y < b.Height;++y) { for(int x=0; x < nWidth; ++x {p[0] = (byte)(255-p[0]);++p;}p += nOffset;}}b.UnlockBits(bmData);return true;}public static bool Grayscale(Bitmap b){//变成黑白BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe{byte * p = (byte *)(void *)Scan0;int nOffset = stride - b.Width*3;byte red, green, blue;for(int y=0;y < b.Height;++y){for(int x=0; x < b.Width; ++x {blue = p[0];green = p[1];red = p[2];p[0] = p[1] = p[2] = (byte)(.299 * red + .587 * green + .114 * blue);p += 3;}p += nOffset;}}b.UnlockBits(bmData);return true;}亮度public static bool Brightness(Bitmap b,int nBrightness){BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte * p = (byte *)(void *)Scan0;int nOffset = stride - b.Width*3; int nWidth = b.Width * 3;for(int y=0;y<b.Height;++y){for (int x = 0; x < nWidth; ++x){int nVal = (int) (p[0] + nBrightness);if (nVal < 0) nVal = 0;if (nVal > 255) nVal = 255;p[0] = (byte)nVal;++p;}p += nOffset;}}b.UnlockBits(bmData);return true;}对比度public static bool Contrast(Bitmap b,int nContrast){if (nContrast < -100) return false;if (nContrast > 100) return false;double pixel = 0, contrast = (100.0+nContrast)/100.0;contrast *= contrast;BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte * p = (byte *)(void *)Scan0;int nOffset = stride - b.Width*3; int nWidth = b.Width * 3;for(int y=0;y<b.Height;++y){for (int x = 0; x < nWidth;++x){ byte color = p[0]; pixel = color/255.0;pixel -= 0.5;pixel *= contrast;pixel += 0.5;pixel *= 255;if (pixel < 0) pixel = 0;if (pixel > 255) pixel = 255;p[0] = (byte) pixel;++p;}p += nOffset;}}b.UnlockBits(bmData);return true;}public static bool Gamma(Bitmap b){BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; byte [] redGamma = new byte [256];byte [] greenGamma = new byte [256];byte [] blueGamma = new byte [256];for (int i = 0; i < 256; ++i){redGamma[i] = (byte)Math.Min(255, (int)(( 255.0 * Math.Pow(i/255.0, 1.0/5)) + 0.5));//其中1.0/5里的5是红色Gamma值。greenGamma[i] = (byte)Math.Min(255, (int)(( 255.0 * Math.Pow(i/255.0, 1.0/5)) + 0.5));blueGamma[i] = (byte)Math.Min(255, (int)(( 255.0 * Math.Pow(i/255.0, 1.0/5)) + 0.5));}unsafe { byte * p = (byte *)(void *)Scan0;int nOffset = stride - b.Width*3; int nWidth = b.Width * 3;byte red, green, blue;for(int y=0;y<b.Height;++y){for (int x = 0; x < b.Width;++x){blue = p[0];green = p[1];red = p[2];p[0]=(byte)blueGamma[(int)blue];p[1]=(byte)greenGamma[(int)green];p[2]=(byte)redGamma[(int)red];p+=3;}p += nOffset;}}b.UnlockBits(bmData);return true;}通道public static bool Channel(Bitmap b,char rgb){ BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte * p = (byte *)(void *)Scan0;int nOffset = stride - b.Width*3; int nWidth = b.Width * 3;byte red, green, blue;for(int y=0;y<b.Height;++y){for (int x = 0; x < b.Width;++x){switch(rgb){case 'r': p[0]=(byte)0;p[1]=(byte)0;break;case 'g':p[0]=(byte)0;p[2]=(byte)0;break;case 'b':p[2]=(byte)0;p[1]=(byte)0;break;}p+=3;}p += nOffset;} }b.UnlockBits(bmData);return true;}--------------------------------------------------------------------------------------------------------
附：对 ASP.NET 图像的颜色量化(Quantization)进行优化
http://www.microsoft.com/china/MSDN/library/archives/library/DNAspp/html/colorquant.asp
浙公网安备 33010602011771号