ECW for MapInfo Help

Transparency support in JP2 images

MapImagery Professional and MapImagery Lite users can switch on support for rendering the alpha layer of a JPEG2000 image as transparent. This support works for both local JP2 images and for streaming images served from an Image Web Server.

Support for this feature requires that a MapImagery Raster file .MIR is generated, in addition to a .TAB file. This file is a replacement for the .URL file generated by previous versions of MapImagery, and contains the URL of the image and also options controling transparency rendering.

To create a registered .TAB file and .MIR file for viewing an Image Web Server JP2 Image, with a transparent layer, perform the following steps:

1. From within MapInfo, choose the MapImagery Options item on the main MapImagery menu. Switch to the Transparency Tab and ensure that the Enable JPEG200 Alpha layer Transparency Support is checked (as shown in the picture below). If this option is disabled then you probably need to obtain a MapImagery Professional or MapImagery Lite license before transparency can be enabled.

2. From within MapInfo, choose the Open ECW or JP2 Image option on the MapImagery menu.

Choose the Open ECW or JP2 Image option from the MapImagery toolbar.

3. Choose how you want to open the JP2 image. To generate a .tab and .mir file suitable for viewing an Image Web Server JP2 image (with a transparent alpha layer) via ECW for MapInfo, choose the options shown in the picture below. (Note that both both local and Image Web Server JP2 images are supported):

4. You should now see the dialog shown below. Enter the URL of the Image Web Server Image. A good way of doing this is to cut and paste the address from a WEB browser, using Control C (to cut from the WEB browser) followed by Control V (to paste into the MapImagery dialog)

5. If a MapInfo .tab file already exists for the algorithm, you will be prompted to confirm that you wish to overwrite the existing .tab file. Note that doing so will overwrite any changes you have made to the projection, units, or tie-point information.

6. MapImagery automatically registers an ECW or JP2 image the first time that you load the image.

You will be shown the following dialog, which shows you the ER Mapper registration details and allows you to select the corresponding MapInfo projection details.

MapImagery saves away the choice that you make for future use. The next time that you try to load an ECW image with the same projection details, the projection dialog will remember the MapInfo Category, Category Member, and Units that you entered, and fill in these values for you.

7.MapInfo should now display the image, and if there is an alpha layer in the JP2 file, those pixels of the image with a zero alpha value will show the background (rather than the original image).

Your image should look something like this, with background showing through where the alpha values are not set:

9.If you disable transparency (via the options dialog shown above), if you don't have a valid MapImagery Professional or MapImagery Lite license, or if your image doesn't have an alpha layer, your image should look something like shown below:

After disabling transparency, press control D to redraw the image.

8. Both the .TAB file and .MIR file (which contains the actual address of the Image Web Server Image) will get saved into the "Default Algorithm Directory", that can be set via the MapImagery Options dialog. You can move both of the files to another directory, as long as they stay together.

Opening Image Web Server URL images in MapInfo