/// <summary>
/// GDAL栅格转换为位图
/// </summary>
/// <param name="ds">GDAL Dataset</param>
/// <param name="showRect">显示区域</param>
/// <param name="bandlist">需要显示的波段列表</param>
/// <returns>返回Bitmap对象</returns>
public Bitmap GetImage(OSGeo.GDAL.Dataset ds, Rectangle showRect, int[] bandlist)
{
int imgWidth = ds.RasterXSize; //影像宽
int imgHeight = ds.RasterYSize; //影像高
float ImgRatio = imgWidth / (float)imgHeight; //影像宽高比
//获取显示控件大小
int BoxWidth = showRect.Width;
int BoxHeight = showRect.Height;
float BoxRatio = imgWidth / (float)imgHeight; //显示控件宽高比
//计算实际显示区域大小，防止影像畸变显示
int BufferWidth, BufferHeight;
if (BoxRatio >= ImgRatio)
{
BufferHeight = BoxHeight;
BufferWidth = (int)(BoxHeight * ImgRatio);
}
else
{
BufferWidth = BoxWidth;
BufferHeight = (int)(BoxWidth / ImgRatio);
}
//构建位图
Bitmap bitmap = new Bitmap(BufferWidth, BufferHeight,
System.Drawing.Imaging.PixelFormat.Format24bppRgb);
//if (bandlist.Length == 3) //RGB显示
//{
// int[] r = new int[BufferWidth * BufferHeight];
// Band band1 = ds.GetRasterBand(bandlist[0]);
// band1.ReadRaster(0, 0, imgWidth, imgHeight, r, BufferWidth, BufferHeight, 0, 0); //读取图像到内存
// //为了显示好看，进行最大最小值拉伸显示
// double[] maxandmin1 = { 0, 0 };
// band1.ComputeRasterMinMax(maxandmin1, 0);
// int[] g = new int[BufferWidth * BufferHeight];
// Band band2 = ds.GetRasterBand(bandlist[1]);
// band2.ReadRaster(0, 0, imgWidth, imgHeight, g, BufferWidth, BufferHeight, 0, 0);
// double[] maxandmin2 = { 0, 0 };
// band2.ComputeRasterMinMax(maxandmin2, 0);
// int[] b = new int[BufferWidth * BufferHeight];
// Band band3 = ds.GetRasterBand(bandlist[2]);
// band3.ReadRaster(0, 0, imgWidth, imgHeight, b, BufferWidth, BufferHeight, 0, 0);
// double[] maxandmin3 = { 0, 0 };
// band3.ComputeRasterMinMax(maxandmin3, 0);
// int i, j;
// for (i = 0; i < BufferWidth; i++)
// {
// for (j = 0; j < BufferHeight; j++)
// {
// int rVal = Convert.ToInt32(r[i + j * BufferWidth]);
// rVal = (int)((rVal - maxandmin1[0]) / (maxandmin1[1] - maxandmin1[0]) * 255);
// int gVal = Convert.ToInt32(g[i + j * BufferWidth]);
// gVal = (int)((gVal - maxandmin2[0]) / (maxandmin2[1] - maxandmin2[0]) * 255);
// int bVal = Convert.ToInt32(b[i + j * BufferWidth]);
// bVal = (int)((bVal - maxandmin3[0]) / (maxandmin3[1] - maxandmin3[0]) * 255);
// Color newColor = Color.FromArgb(rVal, gVal, bVal);
// bitmap.SetPixel(i, j, newColor);
// }
// }
//}
//else //灰度显示
{
int[] r = new int[BufferWidth * BufferHeight];
Band band1 = ds.GetRasterBand(bandlist[0]);
band1.ReadRaster(0, 0, imgWidth, imgHeight, r, BufferWidth, BufferHeight, 0, 0);
double[] maxandmin1 = { 0, 0 };
band1.ComputeRasterMinMax(maxandmin1, 0);
int i, j;
for (i = 0; i < BufferWidth; i++)
{
for (j = 0; j < BufferHeight; j++)
{
int rVal = Convert.ToInt32(r[i + j * BufferWidth]);
rVal = (int)((rVal - maxandmin1[0]) / (maxandmin1[1] - maxandmin1[0]) * 255);
Color newColor = Color.FromArgb(rVal, rVal, rVal);
bitmap.SetPixel(i, j, newColor);
}
}
}
return bitmap;
}
private void GetPreview(OSGeo.GDAL.Dataset dataset, System.Drawing.Size size, Graphics g, IEnvelope bbox)
{
double[] geoTrans = new double[6];
dataset.GetGeoTransform(geoTrans);
GeoTransform GT = new GeoTransform(geoTrans);
int DsWidth = dataset.RasterXSize;
int DsHeight = dataset.RasterYSize;
Bitmap bitmap = new Bitmap(size.Width, size.Height, PixelFormat.Format24bppRgb);
int iPixelSize = 3; //Format24bppRgb = byte[b,g,r]
if (dataset != null)
{
/*
if ((float)size.Width / (float)size.Height > (float)DsWidth / (float)DsHeight)
size.Width = size.Height * DsWidth / DsHeight;
else
size.Height = size.Width * DsHeight / DsWidth;
*/
double left = Math.Max(bbox.MinX, _Envelope.MinX);
double top = Math.Min(bbox.MaxY, _Envelope.MaxY);
double right = Math.Min(bbox.MaxX, _Envelope.MaxX);
double bottom = Math.Max(bbox.MinY, _Envelope.MinY);
int x1 = (int)GT.PixelX(left);
int y1 = (int)GT.PixelY(top);
int x1width = (int)GT.PixelXwidth(right - left);
int y1height = (int)GT.PixelYwidth(bottom - top);
bitmap = new Bitmap(size.Width, size.Height, PixelFormat.Format24bppRgb);
BitmapData bitmapData = bitmap.LockBits(new Rectangle(0, 0, size.Width, size.Height), ImageLockMode.ReadWrite, bitmap.PixelFormat);
try
{
unsafe
{
for (int i = 1; i <= (dataset.RasterCount > 3 ? 3 : dataset.RasterCount); ++i)
{
byte[] buffer = new byte[size.Width * size.Height];
OSGeo.GDAL.Band band = dataset.GetRasterBand(i);
//band.ReadRaster(x1, y1, x1width, y1height, buffer, size.Width, size.Height, (int)GT.HorizontalPixelResolution, (int)GT.VerticalPixelResolution);
band.ReadRaster(x1, y1, x1width, y1height, buffer, size.Width, size.Height, 0, 0);
int p_indx = 0;
int ch = 0;
//#warning Check correspondance between enum and integer values
if (band.GetRasterColorInterpretation() == OSGeo.GDAL.ColorInterp.GCI_BlueBand) ch = 0;
if (band.GetRasterColorInterpretation() == OSGeo.GDAL.ColorInterp.GCI_GreenBand) ch = 1;
if (band.GetRasterColorInterpretation() == OSGeo.GDAL.ColorInterp.GCI_RedBand) ch = 2;
if (band.GetRasterColorInterpretation() != OSGeo.GDAL.ColorInterp.GCI_PaletteIndex)
{
for (int y = 0; y < size.Height; y++)
{
byte* row = (byte*)bitmapData.Scan0 + (y * bitmapData.Stride);
for (int x = 0; x < size.Width; x++, p_indx++)
{
row[x * iPixelSize + ch] = buffer[p_indx];
}
}
}
else //8bit Grayscale
{
for (int y = 0; y < size.Height; y++)
{
byte* row = (byte*)bitmapData.Scan0 + (y * bitmapData.Stride);
for (int x = 0; x < size.Width; x++, p_indx++)
{
row[x * iPixelSize] = buffer[p_indx];
row[x * iPixelSize + 1] = buffer[p_indx];
row[x * iPixelSize + 2] = buffer[p_indx];
}
}
}
}
}
}
finally
{
bitmap.UnlockBits(bitmapData);
}
}
g.DrawImage(bitmap, new System.Drawing.Point(0, 0));
}
