/// <summary>
/// prepares gdal dataset
/// </summary>
protected void PrepareDriver()
{
//create mapserver object
try
{
//make sure gdal is properly set up
ConfigureGdal();
//extract the data source name if not already set
//the driver constructor has a 'layerName' param that can be used to explicitly specify how a layer should be named
if (string.IsNullOrEmpty(this.DataSourceName))
{
this.DataSourceName = System.IO.Path.GetFileNameWithoutExtension(this.DataSource);
}
//open gdal dataset
this.GdalDataset = Gdal.Open(DataSource, Access.GA_ReadOnly);
//work out the raster bounds
double[] adfGeoTransform = new double[6];
this.GdalDataset.GetGeoTransform(adfGeoTransform);
double minx_pix = 0;
double miny_pix = this.GdalDataset.RasterYSize;
double maxx_pix = this.GdalDataset.RasterXSize;
double maxy_pix = 0;
this.RasterMinX = adfGeoTransform[0] + adfGeoTransform[1] * minx_pix + adfGeoTransform[2] * miny_pix;
this.RasterMinY = adfGeoTransform[3] + adfGeoTransform[4] * minx_pix + adfGeoTransform[5] * miny_pix;
this.RasterMaxX = adfGeoTransform[0] + adfGeoTransform[1] * maxx_pix + adfGeoTransform[2] * maxy_pix;
this.RasterMaxY = adfGeoTransform[3] + adfGeoTransform[4] * maxx_pix + adfGeoTransform[5] * maxy_pix;
this.RasterWidth = Math.Abs(this.RasterMaxX - this.RasterMinX);
this.RasterHeight = Math.Abs(this.RasterMaxY - this.RasterMinY);
//collect the roaster overview resolutions
//assume the horisontal and vertical resolutions are the same (which of course may not be true in all cases, but will be ok with this ode usage)
Band band = GdalDataset.GetRasterBand(1);
RasterResolutions = new List <double>();
for (int i = 0; i < band.GetOverviewCount(); i++)
{
var ov = band.GetOverview(i);
RasterResolutions.Add(this.RasterWidth / ov.XSize);
}
//driver seems to be ok so far
this.DriverReady = true;
}
catch (Exception ex)
{
this.DriverReady = false;
this.DriverExceptionMsg = ex.Message;
}
}
/// <summary>
/// Renders the requested image
/// NOTE: jp2 rendering using GDAL can become extremaly heavy on the cpu...
/// so app pool cpu throttling may have to be enabled...
/// in such case though of course all the stuff gonna be a bit rough
/// </summary>
/// <param name="bbox"></param>
/// <param name="width"></param>
/// <param name="height"></param>
/// <param name="imageEncoder"></param>
/// <param name="backColor"></param>
/// <returns></returns>
protected byte[] Render(WmsBoundingBox bbox, int width, int height, ImageCodecInfo imageEncoder, Color backColor)
{
byte[] output = null;
//prepare the output bitmap
var outB = new Bitmap(width, height, PixelFormat.Format32bppArgb);
//Make sure to make the bitmap transparent initially! -> Format32bppArgb
//TODO sometime in the future...
//Add some more sophisticated intersection testing - see hgis/issues/3
//do not render the map if the bbox is outside of the map's bbox
//if any of the below tests yield true, bbox does not intersect with the raster bounds
if (
!(
bbox.MaxX < RasterMinX ||
bbox.MinX > RasterMaxX ||
bbox.MinY > RasterMaxY ||
bbox.MaxY < RasterMinY
)
)
{
//since got here, bbox intersects with the raster bounds so need to read the data
//work out which overview should be used - based on the requested resolution
//the array of resolutions is sorted as it has been collected off the raster
var requestedRes = bbox.Width / width;
var minDiff = Math.Abs(RasterResolutions[0] - requestedRes);
var overviewIdx = 0;
for (int i = 1; i < RasterResolutions.Count; i++)
{
var currentDiff = Math.Abs(RasterResolutions[i] - requestedRes);
if (currentDiff > minDiff)
{
break;
}
overviewIdx = i;
}
//get the overview - need to go through a band
var ov = GdalDataset.GetRasterBand(1).GetOverview(overviewIdx);
//get the resolution of the overview
var ovres = RasterResolutions[overviewIdx];
//work out render area in map units and pixels
double gdal_render_area_left = bbox.MinX < RasterMinX ? RasterMinX : bbox.MinX;
double gdal_render_area_right = bbox.MaxX > RasterMaxX ? RasterMaxX : bbox.MaxX;
double gdal_render_area_top = bbox.MaxY > RasterMaxY ? RasterMaxY : bbox.MaxY;
double gdal_render_area_bottom = bbox.MinY < RasterMinY ? RasterMinY : bbox.MinY;
int gdal_pix_left = (int)((gdal_render_area_left - RasterMinX) / ovres);
int gdal_pix_top = (int)((RasterMaxY - gdal_render_area_top) / ovres);
int gdal_pix_width = (int)((gdal_render_area_right - gdal_render_area_left) / ovres);
int gdal_pix_heigh = (int)((gdal_render_area_top - gdal_render_area_bottom) / ovres);
//bitmap to extract gdal data
var gdalB = new Bitmap(
gdal_pix_width,
gdal_pix_heigh,
PixelFormat.Format32bppArgb
);
//Make sure to make the bitmap transparent initially! -> Format32bppArgb
////example of extracting data for each channel and painting it pixel by pixel
////this is not the most efficient - see below
////-----------
//var sw = System.Diagnostics.Stopwatch.StartNew();
//Band redBand = GdalDataset.GetRasterBand(1).GetOverview(overviewIdx);
//Band greenBand = GdalDataset.GetRasterBand(2).GetOverview(overviewIdx);
//Band blueBand = GdalDataset.GetRasterBand(3).GetOverview(overviewIdx);
//Band alphaBand = GdalDataset.GetRasterBand(4).GetOverview(overviewIdx);
//int[] R = new int[gdalB.Width * gdalB.Height];
//int[] G = new int[gdalB.Width * gdalB.Height];
//int[] B = new int[gdalB.Width * gdalB.Height];
//int[] A = new int[gdalB.Width * gdalB.Height];
//redBand.ReadRaster(gdal_pix_left, gdal_pix_top, gdalB.Width, gdalB.Height, R, gdalB.Width, gdalB.Height, 4, 0);
//greenBand.ReadRaster(gdal_pix_left, gdal_pix_top, gdalB.Width, gdalB.Height, G, gdalB.Width, gdalB.Height, 4, 0);
//blueBand.ReadRaster(gdal_pix_left, gdal_pix_top, gdalB.Width, gdalB.Height, B, gdalB.Width, gdalB.Height, 4, 0);
//alphaBand.ReadRaster(gdal_pix_left, gdal_pix_top, gdalB.Width, gdalB.Height, A, gdalB.Width, gdalB.Height, 4, 0);
//for (int i = 0; i < gdalB.Width; i++)
//{
// for (int j = 0; j < gdalB.Height; j++)
// {
// Color newColor = Color.FromArgb(
// A[i + j * gdalB.Width],
// R[i + j * gdalB.Width],
// G[i + j * gdalB.Width],
// B[i + j * gdalB.Width]
// );
// gdalB.SetPixel(i, j, newColor);
// }
//}
//sw.Stop();
////---------------
//lock the actual part of the bitmap that should be painted!!!!
BitmapData bitmapData = gdalB.LockBits(
new Rectangle(0, 0, gdalB.Width, gdalB.Height),
ImageLockMode.ReadWrite,
PixelFormat.Format32bppArgb //Make sure to make the bitmap transparent initially! -> Format32bppArgb; otherwise bitmap will not be transparent even though apha channel is extracted!
);
try
{
int stride = bitmapData.Stride;
IntPtr buf = bitmapData.Scan0;
//Notes
//so far expecting rgb or argb image!
//TODO
//properly handle grayscale / palletted images
////example of readin raster off the dataset
////---------
//int[] bandmap = null;
//if (GdalDataset.RasterCount == 4)
//{
// //rgba -> bgra
// bandmap = new int[] { 3, 2, 1, 4 };
//}
//else if (GdalDataset.RasterCount == 3)
//{
// //rgb -> bgr
// bandmap = new int[] { 3, 2, 1 };
//}
//else
//{
// throw new Exception("So far hgis.Gdal wms driver so far does not support neither grayscale nor palleted rasters");
//}
////How to read a particular overview?????
//GdalDataset.ReadRaster(
// gdal_pix_left - gdal_margin_left,
// gdal_pix_top - gdal_margin_top,
// gdalB.Width,
// gdalB.Height,
// buf,
// gdalB.Width,
// gdalB.Height,
// DataType.GDT_Byte,
// GdalDataset.RasterCount,
// bandmap,
// 4,
// stride,
// 1
//);
///---------
//get the bands for an overview
Band redBand = GdalDataset.GetRasterBand(1).GetOverview(overviewIdx);
Band greenBand = GdalDataset.GetRasterBand(2).GetOverview(overviewIdx);
Band blueBand = GdalDataset.GetRasterBand(3).GetOverview(overviewIdx);
//read blue
blueBand.ReadRaster(
gdal_pix_left,
gdal_pix_top,
gdalB.Width,
gdalB.Height,
buf,
gdalB.Width,
gdalB.Height,
DataType.GDT_Byte,
4,
stride
);
//green
greenBand.ReadRaster(
gdal_pix_left,
gdal_pix_top,
gdalB.Width,
gdalB.Height,
new IntPtr(buf.ToInt64() + 1),
gdal_pix_width,
gdal_pix_heigh,
DataType.GDT_Byte,
4,
stride
);
//red
redBand.ReadRaster(
gdal_pix_left,
gdal_pix_top,
gdalB.Width,
gdalB.Height,
new IntPtr(buf.ToInt64() + 2),
gdalB.Width,
gdalB.Height,
DataType.GDT_Byte,
4,
stride
);
if (GdalDataset.RasterCount > 3)
{
Band alphaBand = GdalDataset.GetRasterBand(4).GetOverview(overviewIdx);
alphaBand.ReadRaster(
gdal_pix_left,
gdal_pix_top,
gdalB.Width,
gdalB.Height,
new IntPtr(buf.ToInt64() + 3),
gdalB.Width,
gdalB.Height,
DataType.GDT_Byte,
4,
stride
);
}
}
finally
{
gdalB.UnlockBits(bitmapData);
}
//at this stage raster data should have been extracted, so now need to paint it over the output bitmap
//work out the offset of the gdal raster
double requestedResX = bbox.Width / width;
double requestedResY = bbox.Height / height;
//initially assume the image is completely within the raster bounds
int pixl = 0, pixt = 0, pixw = width, pixh = height;
//adjust the destination rect in a case bbox intersects with the raster bounds
if (bbox.MinX < gdal_render_area_left)
{
pixl = (int)(Math.Abs(gdal_render_area_left - bbox.MinX) / requestedResX);
pixw -= pixl;
}
if (bbox.MaxX > gdal_render_area_right)
{
pixw -= (int)(Math.Abs(bbox.MaxX - gdal_render_area_right) / requestedResX);
}
if (bbox.MaxY > gdal_render_area_top)
{
pixt = (int)(Math.Abs(bbox.MaxY - gdal_render_area_top) / requestedResY);
pixh -= pixt;
}
if (bbox.MinY < gdal_render_area_bottom)
{
pixh -= (int)(Math.Abs(gdal_render_area_bottom - bbox.MinY) / requestedResY);
}
//paint the gdal raster on the output bitmap
using (Graphics g = Graphics.FromImage(outB))
{
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.NearestNeighbor;
//make sure the edge pixels are not taken into account when interpolating
//for details check out http://www.codeproject.com/Articles/11143/Image-Resizing-outperform-GDI
using (ImageAttributes wrapMode = new ImageAttributes())
{
wrapMode.SetWrapMode(System.Drawing.Drawing2D.WrapMode.TileFlipXY);
//next the rendered bitmap
g.DrawImage(
gdalB,
new Rectangle(pixl, pixt, pixw, pixh), //dest rect
0, 0, gdalB.Width, gdalB.Height, //source rect
GraphicsUnit.Pixel,
wrapMode
);
}
}
}
//if transparent, just use the out bitmap as it is already transparent
//if not transparent, but back color set, then paint the pitmap with that color
if (backColor != Color.Transparent)
{
//TODO
var backB = new Bitmap(width, height, PixelFormat.Format24bppRgb); //use 24 bit bitmap as it is not transparent
//paint the base image with the required back colour
using (Graphics g = Graphics.FromImage(backB))
{
//first paint the background color
g.FillRectangle(
new SolidBrush(backColor),
0,
0,
backB.Width,
backB.Height
);
//next the rendered bitmap
g.DrawImage(
outB,
new Rectangle(0, 0, backB.Width, backB.Height), //dest rect
new Rectangle(0, 0, outB.Width, outB.Height), //source rect
GraphicsUnit.Pixel
);
}
outB = backB;
}
using (var ms = new MemoryStream())
{
outB.Save(ms, imageEncoder, null);
output = ms.ToArray();
}
return(output);
}