Shulou(Shulou.com)06/01 Report--

1. Preface

In actual projects, we often encounter such a scenario: the base map of the map may be an Internet map (Baidu, Gaud, Tiandi Map), etc., while we have a separate set of POI data for a certain area, we need to mask the original POI data of this area in the Internet map and only display our own POI data.

In response to this requirement, the first thing we thought about was whether we could use only the underlay tiles that did not contain annotations, and then superimpose our POI data. In fact, one more thing to consider in the actual demand is that we only have POI data for some regions, but not POI data for other regions.

So the real core of this demand is: except for the designated area of irregular polygons, maps are Internet maps plus Internet annotations, and this core area needs to be Internet maps plus their own annotations.

two。 Scheme thinking

a. Throughout the range of the map, the Internet base map and the Internet annotation map are still superimposed as the base map.

b. Overlay the Internet base map of the area again, which can be regarded as a mask to mask the annotation layers in the range.

c. Cut the corrected custom POI layer and overlay it into the map as the top layer.

The order of the map layers is as follows:

3. Difficulties to be solved

a. Tile splicing technology: you need to splice the downloaded tiles of the specified area into a whole, and then PS the area.

b. Image segmentation technology: the area map after PS needs to be divided according to tile size.

c. Tile renaming: the split tile needs to be re-assigned according to the corresponding row number.

4. Realize

The specific code implementation process is realized by my good × × × smear without bitterness, thank you, continue to work hard.

4.1 tile download

Use the self-developed tile download tool to download the Internet base map of the specified area, the principle can refer to my previous blog: WebGIS through the row number to convert a variety of tile URL online map (http://www.cnblogs.com/naaoveGIS/p/3905523.html)).

4.2 tile splicing and PS4.2.1 splicing principle

The tiles of the same level are spliced into a whole picture according to the row number.

4.2.2 use PS to matting the stitched image

It should be noted here that each level of the map needs to be spliced into a corresponding level of the whole picture, and PS also needs to matte the whole picture of each level.

4.3 Image segmentation and assignment of row number

a. Read the original spliced tile folder and get the row number name of the original tile in turn.

b. The whole image after matting is divided according to the specified size of tiles.

c. The split graph is given the name of the original tile row number.

5. Effect display

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