Export all components of given type from manifold map file

You may sometime need to export all the components of given type so they can be used in another GIS environment. Here goes a script that does exactly this. The example exports all the drawings and tables to either shp or xls:

using Manifold.Interop.Scripts;
using M = Manifold.Interop;

class Script {
	static void Main() {
		//Some setup stuff first
        string exportFld = "H:\\ExportedComponents\\";

        M.Application mApp = Context.Application;
        M.Document mDoc = (M.Document)mApp.ActiveDocument;
        M.ComponentSet mCompSet = mDoc.ComponentSet;

        //Exporters
        M.ExportShp shpExporter = (M.ExportShp)mApp.NewExport("SHP");
        shpExporter.ConvertPolicy = M.ConvertPolicy.ConvertAll;

        M.ExportXls xlsExporter = (M.ExportXls)mApp.NewExport("XLS");
        xlsExporter.ConvertPolicy = M.ConvertPolicy.ConvertAll;

       //iterate through all components
        for (int i = 0; i < mCompSet.Count; i++ )
        {
            mApp.StatusText = "Reading component " + i.ToString() + " of " + mCompSet.Count;

            switch (mCompSet[i].Type)
            {
                case M.ComponentType.ComponentDrawing:

                    shpExporter.Export(mCompSet[i], exportFld + mCompSet[i].Name + shpExporter.DefaultExtension, M.ConvertPrompt.PromptNone);

                    break;

                case M.ComponentType.ComponentTable:

                    xlsExporter.Export(mCompSet[i], exportFld + mCompSet[i].Name + xlsExporter.DefaultExtension, M.ConvertPrompt.PromptNone);
                    break;
            }
        }

        mApp.StatusText = "";
        mApp.MessageBox("Done!", "Info");
	}
}

Upload and save image in a database - ExtJs and ASP.NET

It's been a while since the last post appeared here so this one will be rather longish ;-)

Recently in one of our projects we had a requirement to allow users to upload their images to the database so they can later be viewed by other users of the application.

For the clientside we used the ExtJs framework while the serverside was ASP.NET and c#.

Basically the process can be divided into three parts: image upload on the clientside, image processing on the server side and also image retrieval from the database so it can be displayed again in a browser.

More...

Creating a cost surface in Manifold

Recently I have played a bit with manifold to find out how to prepare a cost surface. There are no out of the box tools in manifold to magically create such a surface but a bit of sql does the job.

Lets assume we have two components - a surface and a drawing. Surface will be a container for our output data and the drawing will provide the input - in this case a bunch of simple lines imitating a road or stream network.

Lets start with preparing an output surface - simply copy the drawing and paste it as a surface and when done run an update query to set the cell values to 0:

UPDATE [Surface] SET [Height (I)] = 0

When our surface is ready we can start playing with generating a cost surface (in this case this will be a distance from the nearest vector object):

UPDATE
(SELECT
	[Surface].[Height (I)],
	Distance(
		AssignCoordsys(
			NewPoint([Center X (I)],[Center Y (I)]),
			CoordSys("Surface" AS COMPONENT)
		),
		Line.[Geom]
	) AS [Distance]
FROM
	[Surface],
	(SELECT AllBranches([Drawing].[Geom (I)]) As [Geom]
	FROM [Drawing]) AS Line)
SET [Height (I)] = [Distance];

 After running this query our surface should look like this:

So far s good but let's have a look at raster reclassification to make the output a bit more useful for further usage. We can write another query that will update our already generated surface, though for this example I have decided to combine it with the query above:

UPDATE
(SELECT
	[Surface].[Height (I)],
	Distance(
		AssignCoordsys(
			NewPoint([Center X (I)],[Center Y (I)]),
			CoordSys("Surface" AS COMPONENT)
		),
		Line.[Geom]
	) AS [Distance]
FROM
	[Surface],
	(SELECT AllBranches([Drawing].[Geom (I)]) As [Geom]
	FROM [Drawing]) AS Line)
SET [Height (I)] = 
	CASE
		WHEN  [Distance] < 5 THEN 0
		WHEN  [Distance] < 10 THEN 1
		WHEN  [Distance] < 15 THEN 2
		WHEN  [Distance] < 20 THEN 3
		WHEN  [Distance] < 25 THEN 4
		WHEN  [Distance] < 30 THEN 5
		WHEN  [Distance] < 35 THEN 6
		WHEN  [Distance] < 40 THEN 7
		WHEN  [Distance] < 45 THEN 8
		ELSE 9
	END

 So now our surface looks like this:

What's next? Having prepared more surfaces for analysis one can now combine them using surface tools. If surface tools are not avaialble it is easy enough to combine surfaces using the UPDATE technique shown above.

If you want to play a bit with the examples shown here just download this file: example.map (1.00 mb)

Printing a OpenLayers map in ASP.NET

Printing a map created in OpenLayers or other commercial APIs is still not that easy. There are some problems with transparency of the gif and png images but also with the transparency of the vector canvas used to display vectors. It is possible though to print a road map or layers that do not use transparency without problems. What if we use transparent overlays or vector layers? If our project is utilising geoserver then the problem is solved - there is a mapfish printing module available for geoserver and it does a great job. What if the project does not utilise geoserver but some other custom data sources? Well, we'll need to do some work serverside.

In order to do a serverside tile stitching we will need to collect some data on the clientside so we can then grab all the necessary tiles and assemble them together into one piece:

var tiles = [];
for (var l = 0; l < map.layers.length; l++) {

	//grab the layer
	var layer = map.layers[l];
		
	//skip vector layers	
	if (layer.isVector) continue;

	//now check if it is visible and in range (wms)	
	if (!layer.getVisibility()) continue;
	if (!layer.calculateInRange()) continue;

	// iterate through their grid's tiles, collecting each tile's extent and pixel location at this moment
	for (var r = 0; r < layer.grid.length; r++) { //tile rows (grid is an array of rows)
		for (var c = 0; c < layer.grid[r].length; c++) {//columns

			//grab the tile
			var tile = layer.grid[r][c];

			//when using round there would be some gaps between tiles from time to time so ceil is used instead
			var tilePosX = Math.ceil((tile.bounds.left - mapBounds.left) / resolution);
			var tilePosY = Math.ceil((mapBounds.top - tile.bounds.top) / resolution);                 

			//get the layer opacity
			var opacity = layer.opacity ? parseInt(100 * layer.opacity) : 100;

			//collect data for a tile
			tiles[tiles.length] = {
				url: layer.getURL(tile.bounds),
				x: tilePosX,
				y: tilePosY,
				tileSizeW: layer.tileSize.w,
				tileSizeH: layer.tileSize.h,
				opacity: opacity
			};
		}
	}
}

//data to be sent to the serverside
var printData = {
	mapPixWidth: map.getSize().w,
	mapPixHeight: map.getSize().h,
	tileData: tiles
}

If you searched for some OpenLayers printing examples you may have found examples that use:

tile.position.x,
tile.position.y

instead of:

tilePosX = Math.ceil((tile.bounds.left - mapBounds.left) / resolution);
tilePosY = Math.ceil((mapBounds.top - tile.bounds.top) / resolution);

This is quite weird as I expected both yield the same results but when using OpenLayers within ExtJs layouts I encountered some strange results and found out there were some tile origin positioning shifts. Using the 'manual' tile origin calculation seems to fix the problem so I decided to stay with the adjusted code of course ;)

Since we have the tile data collected already it is the time to move to the serverside. The job to be done here is to download all the necessary tiles (the ones that overlap with the map's viewport), stitch them together and save the final image to jpeg, png, pdf, etc.

I had to do printing to jpeg so the example will use jpeg output.

In order to stitch the images together I had to download them first:

//downloads a remote image from given url
private System.Drawing.Bitmap grabImageFromWeb(string requestUrl, int tileWidth, int tileHeight)
{
    //output image
    System.Drawing.Bitmap outputImage = new System.Drawing.Bitmap(tileWidth, tileHeight);

    //test if the request string was passed and if so request data from the destination server
    if (requestUrl != null)
    {
        //create a new HttpWebRequest
        System.Net.HttpWebRequest webRequest;
        webRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(requestUrl);
        webRequest.Method = "GET";

        System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)webRequest.GetResponse();

        //check if the data was successfully retrieved
        if (response.StatusCode.ToString().ToLower() == "ok")
        {
            System.IO.Stream stream = response.GetResponseStream();
            outputImage = (System.Drawing.Bitmap)System.Drawing.Image.FromStream(stream);
        }
    }

    return outputImage;
}

 Having created a method to grab the images off the web I could now do the actual tile collection and stitching (the output of the code below is an image that maps 1:1 to the map extent visible at the user's display):

//output bitmap
System.Drawing.Bitmap mapBitmap = new System.Drawing.Bitmap(printData.mapPixWidth, printData.mapPixHeight);

//compose the map image
using (System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(mapBitmap))
{
    //stitch all the tiles together 
    for (int t = 0; t < printData.tileData.Length; t++)
    {
        //test if a tile overlaps with the output image and grab it only if so
        //tile origin + tile size must be > 0
        //and tile origin < bitmap size
        if (printData.tileData[t].x + printData.tileData[t].tileSizeW > 0 && printData.tileData[t].x < mapBitmap.Width && printData.tileData[t].y + printData.tileData[t].tileSizeH > 0 && printData.tileData[t].y < printData.mapPixHeight)
        {
            g.DrawImage(
                grabImageFromWeb(printData.tileData[t].url, printData.tileData[t].tileSizeW, printData.tileData[t].tileSizeH), //source image
                new System.Drawing.Rectangle(printData.tileData[t].x, printData.tileData[t].y, printData.tileData[t].tileSizeW, printData.tileData[t].tileSizeH),//destination rect
                new System.Drawing.Rectangle(0, 0, printData.tileData[t].tileSizeW, printData.tileData[t].tileSizeH),//source rect
                System.Drawing.GraphicsUnit.Pixel //drawing unit
            );
        }
    }
}

//output file name
string fileName = "Printout_" + DateTime.Now.Ticks.ToString() + ".jpg";

//save bitmap
pageBitmap.Save(Server.MapPath (System.Configuration.ConfigurationSettings.AppSettings["printedFiles"] + "\\" + fileName), System.Drawing.Imaging.ImageFormat.Jpeg);

There are a few things worth remembering here:

  • google layers will not print as there is no direct access to the google tiles through OpenLayers. OL 3.0 though should have direct access to the Bing Maps tiles, so it should be possible to create a printout off the Bing tiles
  • when collecting the tile data I was testing for a few conditions specific to my set up, you may require some more tests (for example if you have gmaps layers the js example shown here will fail as gmaps layer does not have a grid property
  • there may be some other issues with the code shown but the generic idea should be easy to follow
  • with a bit more work one could collect vector data as well and draw the features on the top of the stitched tiles (I actually did it for my app but it wouldn't make sense to show it here as the code was simply too customised)

ASP.NET xDomainProxy for OpenLayers getInfo requests

After a long time of just talking about using geoserver we have eventually installed it on our server. Making it work behind IIS is a subject for another article and I am hoping to post it soon.

Anyway, we decided to make our geoserver available at geoserver.cartoninjas.net, while the applications we write are likely to be hosted under different subdomains or even under different domains. Since x-domain requests are not allowed in JavaScript due to some security restrictions I needed to create a simple server side proxy that would be exposed to application as a local resource and would take care of pulling the info when a getInfo requests are issued by OpenLayers.

I started with setting up a proxyHost in OpenLayers:

//proxy host
OpenLayers.ProxyHost = 'xDomainProxy.ashx?url=';

Then a server side script for a generic handler:

<%@ WebHandler Language="C#" Class="xDomainProxy" %>

using System;
using System.Web;

public class xDomainProxy : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {

        //OpenLayers.ProxyHost = 'xdomainProxy.aspx?url=' so the requested url is passed in a url param
        string requestUrl = HttpUtility.UrlDecode(context.Request.QueryString["url"]);

        //test if the request string was passed and of so request data from the destination server
        if (requestUrl != null)
        {
            //create a new HttpWebRequest
            System.Net.HttpWebRequest webRequest;
            webRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(requestUrl);
            webRequest.Method = "GET";

            System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)webRequest.GetResponse();

            //check if the data was successfully retrieved
            if (response.StatusCode.ToString().ToLower() == "ok")
            {
                //set the appropriate response content type
                context.Response.ContentType = response.ContentType;

                //Read the stream associated with the response.
                System.IO.StreamReader reader = new System.IO.StreamReader(response.GetResponseStream());

                //and write it to response
                context.Response.Write(reader.ReadToEnd());
            }
        }
    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }
}

And voila, it's ready to be used ;)

A side note: although in many cases this proxy will work properly this is a mini version of the code and should not be implemented in the production environment - it does not catch any errors and will fail if the connection is not available. Also it was written to work with OpenLayers specifically (OpenLayers.ProxyHost) and needs some extra work before it can act as a bit more flexible proxy allowing one to pull data without having to escape the passed url.