[英]C# - Converting 8-bit or 16-bit grayscale raw pixel data
I need to be able to convert 8-bit or 16-bit grayscale pixel data into a file format that the .NET framework can support. 我需要能够将8位或16位灰度像素数据转换为.NET框架可以支持的文件格式。
The data I have available is the width, height, orientation (bottom-left) and the pixel format as 4096 shades of gray (12-bit resolution) packed in 2 bytes per pixel. 我可用的数据是宽度,高度,方向(左下角)和像素格式为4096灰度(12位分辨率),每像素2个字节。
So for example each pixel ranges from 0 to 4096, and each pixel is 2 bytes. 因此,例如,每个像素的范围从0到4096,并且每个像素是2个字节。
I have already tried using PixelFormat.Format16bppGrayScale with the Bitmap constructor, and it throws a GDI+ exception. 我已经尝试使用PixelFormat.Format16bppGrayScale和Bitmap构造函数,它会引发GDI +异常。 Everything I have read says that this format is not supported and that MSDN is wrong. 我读过的所有内容都说不支持这种格式,并且MSDN错误。
I want to convert this pixel buffer into a .NET Bitmap format (such as Format32bppArgb) with as little image quality loss as possible. 我想将此像素缓冲区转换为.NET位图格式(如Format32bppArgb),尽可能减少图像质量损失。
Anyone know how? 谁知道怎么样?
See the example below, which precomputes a lookup table (LUT) and uses that to convert each pixel. 请参阅下面的示例,该示例预先计算查找表(LUT)并使用它来转换每个像素。 This version covers your 12-bit case; 此版本涵盖您的12位案例; for 8-bit the code is very similar, but it is difficult to generalize across pixel formats. 对于8位代码非常相似,但很难概括像素格式。
A conversion from 12-bit GS to effectively 8-bit GS will lose data. 从12位GS到有效8位GS的转换将丢失数据。 However, you can adjust the LUT table to focus on a smaller range of input values with better contrast (ex. DICOM Window Center/Window Width ). 但是,您可以调整LUT表以聚焦较小范围的输入值,并获得更好的对比度(例如DICOM窗口中心/窗口宽度 )。
class Program
{
static void Main( string[] args )
{
// Test driver - create a Wedge, convert to Bitmap, save to file
//
int width = 4095;
int height = 1200;
int bits = 12;
byte[] wedge = Wedge( width, height, bits );
Bitmap bmp = Convert( wedge, width, height, bits );
string file = "wedge.png";
bmp.Save( file );
Process.Start( file );
}
static Bitmap Convert( byte[] input, int width, int height, int bits )
{
// Convert byte buffer (2 bytes per pixel) to 32-bit ARGB bitmap
var bitmap = new Bitmap( width, height, PixelFormat.Format32bppArgb );
var rect = new Rectangle( 0, 0, width, height );
var lut = CreateLut( bits );
var bitmap_data = bitmap.LockBits( rect, ImageLockMode.WriteOnly, bitmap.PixelFormat );
ConvertCore( width, height, bits, input, bitmap_data, lut );
bitmap.UnlockBits( bitmap_data );
return bitmap;
}
static unsafe void ConvertCore( int width, int height, int bits, byte[] input, BitmapData output, uint[] lut )
{
// Copy pixels from input to output, applying LUT
ushort mask = (ushort)( ( 1 << bits ) - 1 );
int in_stride = output.Stride;
int out_stride = width * 2;
byte* out_data = (byte*)output.Scan0;
fixed ( byte* in_data = input )
{
for ( int y = 0; y < height; y++ )
{
uint* out_row = (uint*)( out_data + ( y * in_stride ) );
ushort* in_row = (ushort*)( in_data + ( y * out_stride ) );
for ( int x = 0; x < width; x++ )
{
ushort in_pixel = (ushort)( in_row[ x ] & mask );
out_row[ x ] = lut[ in_pixel ];
}
}
}
}
static uint[] CreateLut( int bits )
{
// Create a linear LUT to convert from grayscale to ARGB
int max_input = 1 << bits;
uint[] lut = new uint[ max_input ];
for ( int i = 0; i < max_input; i++ )
{
// map input value to 8-bit range
//
byte intensity = (byte)( ( i * 0xFF ) / max_input );
// create ARGB output value A=255, R=G=B=intensity
//
lut[ i ] = (uint)( 0xFF000000L | ( intensity * 0x00010101L ) );
}
return lut;
}
static byte[] Wedge( int width, int height, int bits )
{
// horizontal wedge
int max = 1 << bits;
byte[] pixels = new byte[ width * height * 2 ];
for ( int y = 0; y < height; y++ )
{
for ( int x = 0; x < width; x++ )
{
int pixel = x % max;
int addr = ( ( y * width ) + x ) * 2;
pixels[ addr + 1 ] = (byte)( ( pixel & 0xFF00 ) >> 8 );
pixels[ addr + 0 ] = (byte)( ( pixel & 0x00FF ) );
}
}
return pixels;
}
}
Spoof a 16b format & use ColorMatrix to map it correctly before display. 欺骗16b格式并使用ColorMatrix在显示之前正确映射它。
I haven't done performance tests of this approach on Windows, but on other platforms (eg, Android) where I needed efficient memory storage and rapid remapping of different ranges in the 12b or 16b data I've made good use of this technique. 我还没有在Windows上对这种方法进行性能测试,但在其他平台(例如Android)上我需要高效的内存存储并快速重新映射12b或16b数据中的不同范围我已经很好地利用了这种技术。
I tell it my 12/16b grayscale data is really RGB565, so that it's happy serializing, deserializing & other manipulations. 我告诉它我的12 / 16b灰度数据真的是RGB565,所以它很高兴序列化,反序列化和其他操作。 When I need to display I pass it through a ColorMatrix which maps the appropriate window to an 8b grayscale in ARGB8888. 当我需要显示时,我将它传递给ColorMatrix,它将适当的窗口映射到ARGB8888中的8b灰度。
If anyone wants to try this I'll post my mapping algorithm. 如果有人想尝试这个我会发布我的映射算法。
Two possible ways: 两种可能的方式:
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