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LayerOverlay Draw to Bitmap

#1

Scenario:

I have a local RasterTileCache that I am displaying using a LayerOverlay with IsCacheOnly set to true and the TileCache set appropriately. There are no layers. The user will not have access to the TileCache source data.

Question:

How do I have the LayerOverlay draw to a GeoCanvas?

Goal:

I want a bitmap/png of the current map extent to save to a file.

Additional Information:

There is no draw method for the overlay, and there is no layer to draw. I have tried to use MBTilesLayer, but that is expecting a Vector Tile Cache to draw. It does not draw from the RasterTileCache when I try to draw it on the canvas. I have tried to use a CloudRasterLayer, but it gives me an unauthorized exception most of the time. Plus, the tile cache is local, and when I have gotten the CloudRaster layer to draw, it has had holes in the image – meaning that the drawing was incomplete plus it was not the extent that the canvas was set for. My other layers draw as expected.

I nearly forgot to add. I have tried to override the RasterTileCache, but the merge bitmaps is not exposed to me in the Blazor edition like it was in the WPF/Desktop edition.

Thanks for any help that you can offer.

#2

Hi Brandon,

Our developer build a sample for your requirement:

DrawingToGeoCanvas.zip (2.1 MB)

Please try it and please feel free to let us know If we misunderstand anything.

Regards,

Ethan

#3

ModFiles.zip (1.2 KB)

Ethan,

Thanks for the code. I had actually tried something very similar. I modified your sample to what my case is. When I use your sample, it works as expected, but with my settings, it does not.

I modified the Index.Razor, and I enclosed the png. The size limit doesn’t allow me to upload the entire project.

#4

Hi Brandon,

Thanks for your update, our developer look into your scenario and here is a new sample project.

DrawingToGeoCanvas.zip (1.6 MB)

Please view it and I hope that helps resolve the issue for you.

Regards,

Ethan

#5

Ethan,

I appreciate the updated code, but unfortunately, it produces the same result - a blank file.

#6

Hi Brandon,

Could you please try to debug code, and add a break point in CustomLayerOverlay class to see whether it hit?

I download the new package again, and run it in an clean machine, the result is correct.

As below is my test result:

9699
9699688×935 293 KB

If you found anything I missed when test please let me know.

Regards,

Ethan

#7

Is that a shp file that you are trying to show me that displays?

If so, we agree that one works. My scenario is an overlay with NO layers and IsCacheOnly=True and a Raster tile cache setup, which does not work.

A break point hits with a blank output.

#8

Hi Brandon,

Our latest sample project don’t contains shape files, it only contains some cached images, and the IsCacheOnly is set equal true.

<CustomLayerOverlay Id="CustomOverlay" @ref="baseOverlay" IsCacheOnly="true" TileCache="@TileCache"></CustomLayerOverlay>

Could you please double check whether the file you downloaded is 1.55 MB? Because the new version project have the same name with old one.

Regards,

Ethan

#9

Ethan,

That was my mistake. I used the right project this morning (I remember distinctly some of the new code), but I must have looked at the wrong output file. It works as expected. Thanks! :smiley: :smiley: :smiley:

#10

Hi Brandon,

I am glad to hear that’s helpful.

Any question please let us know.

Regards,

Ethan