问题描述
我正在为Android Maps v2 TileOverlay构建图像.举例来说，假设我希望某个像素会以一种特定的颜色出现，该像素最终会在图块中以特定的纬度和经度结束.我怎么知道图块中的哪些经度和纬度将映射到图像中的哪些像素?
I'm building an image for an Android maps v2 TileOverlay. Say, for example, that I want a pixel that will end up at a particular latitude and longitude in the tile, to be a particular color. How do I know what latitudes and longitudes in the tile will map to which pixels in my image?
图块从{latInTile，lngInTile}到{pixelLocationX，pixelLocationY}的映射是什么?
What is the mapping from {latInTile,lngInTile} to {pixelLocationX, pixelLocationY} for a tile?
谢谢.
推荐答案
这正是投影"的含义. Google使用墨卡托投影，如 https://en.wikipedia.org/wiki/Mercator_projection 所述
This is exactly what a "projection" is. Google uses the Mercator Projection, described here https://en.wikipedia.org/wiki/Mercator_projection.
映射为:
pixelLocationX = longitude
pixelLocationY = ln(tan(latitude/2 + Pi/4))
经度和纬度以弧度为单位.然后必须将像素位置缩放到所需的任何单位.
where longitude and latitude are in radians. Pixel locations then have to be scaled to whatever units you need.
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