GIS | 利用GDAL库读写影像数据

基于Dataset 

public CPLErr ReadRaster(int xOff, int yOff, int xSize, int ySize, byte[] buffer, int buf_xSize, int buf_ySize, int bandCount, int[] bandMap, int pixelSpace, int lineSpace, int bandSpace)

int[] dataArray = new int[srcWidth * srcHeight * bandCount];

xOff和yOff是指偏移量，即从影像的左上角起始坐标（xOff,yOff）开始读取数据。

xSize和ySize是指读取图像数据的行列数，即宽度和高度，单位都是像素。

Buffer是图像数据缓存区域（数组），要根据文件类型重新定义 const char*   GDALGetDataTypeName(poBand->GetRasterDataType())  。

buf_xSize和buf_ySize是缓存区的大小，默认的GDAL支持重采样，它们须与buffer申请的大小保持一致，通过这两个参数可以控制影像的缩放，如果它们小于xSize和ySize就是将原图缩小，反之如果它们大于xSize和ySize就是将原图放大。

pixelSpace和lineSpace一般默认取0即可。ReadRaster最后三个参数全是0，默认按照波段顺序存储 。

pixelSpace设置成1，则隔一个像素点读取一个像素点的方式读取图像。

Ds.ReadRaster(0, 0, srcWidth, srcHeight, dataArray, srcWidth, srcHeight, bandCount, bandArray, 0, 0, 0);

 

public CPLErr WriteRaster(int xOff, int yOff, int xSize, int ySize, byte[] buffer, int buf_xSize, int buf_ySize, int pixelSpace, int lineSpace)

        /// <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;
        }

 

读写影像数据（基于Band）

public CPLErr ReadRaster(int xOff, int yOff, int xSize, int ySize, byte[] buffer, int buf_xSize, int buf_ySize, int pixelSpace, int lineSpace)