Using Custom Maps in an iPhone App: A Step-by-Step Guide

Introduction

In this guide, we will explore how to use custom maps in an iPhone app. We’ll dive into the world of map tiles, compression techniques, and scripting magic to bring your own campus university map onto the World map.

Background on Map Tiles

Map tiles are a fundamental component of modern mapping applications. They allow us to display a seamless and detailed representation of the Earth’s surface by dividing it into small, square tiles that can be easily composed to form larger images. Each tile is typically stored as a PNG image with dimensions of 256x256 pixels.

Choosing a Map Tiling Library

When it comes to working with map tiles, there are several libraries and tools available for iOS development. In this guide, we’ll focus on two popular options: OpenStreetMap (OSM) and MapTiler. While OSM provides a rich source of geospatial data, its mapping engine can be complex to work with. MapTiler, on the other hand, offers a more straightforward approach to using custom maps.

Scripting for Map Tiling

To create our own map tiles, we’ll need a scripting tool that can handle PNG images. In this case, we’ll rely on Bash scripting for the task.

Understanding Map Tiling

Before diving into the script, let’s break down how map tiling works:

1. Tile Generation: The first step is to generate the map tiles from your custom map image. This involves dividing the image into smaller squares (tiles) and saving each tile as a separate PNG file.
2. Tile Compression: After generating the tiles, it’s essential to compress them using lossy compression techniques to reduce their size without compromising image quality.
3. Map Tiling: Finally, we’ll use these compressed tiles to create our custom map layer.

Scripting for Map Generation

Here’s a sample Bash script that demonstrates how to generate and compress PNG images:

#!/bin/bash

# Set the directory path where the original map image is stored
MAP_DIR="/path/to/your/map/image"

# Find all PNG files in the specified directory with a minimum depth of 2 (i.e., not top-level directories)
find $MAP_DIR -type f -maxdepth 3 -mindepth 2 -name "*.png" | while read I; do
    # Extract the filename without extension
    OLDNAME=$(basename "$I" .png)

    # Calculate the new tile number by shifting to the left (for example, $SEP1 = map[0-9]+)
    SEP1=${I#./}
    NEWNAME=$((2**$SEP1-$OLDNAME-1))

    # Move the original file to a new location with the updated name
    mv "$I" "$MAP_DIR/$NEWNAME.png"
done

Compression Techniques

To reduce the size of our map tiles, we’ll use lossy compression techniques. The pngcrush command is an excellent tool for this purpose:

#!/bin/bash

# Set the directory path where the compressed map images are stored
COMPRESSED_MAP_DIR="/path/to/your/compressed/map/images"

# Find all PNG files in the specified directory (pre-compressed tiles)
find $MAP_DIR -type f -maxdepth 3 -mindepth 2 -name "*.png" | while read I; do
    # Compress each tile using pngcrush and move it to a new location
    pngcrush -z "$I" "$COMPRESSED_MAP_DIR/$(basename "$I" .png)"
done

Combining Tiles with Route-me

Now that we have our compressed map tiles, let’s discuss how to combine them with the Route-me project.

First, you need to set up your custom map tile server using MapTiler. This will involve creating a new account on their website and following their instructions for setting up your own tile server.

Using Route-me

To use Route-me in conjunction with our custom map tiles:

1. Create a new route: Using the GUI interface or by editing the routes.json file manually.
2. Define the tile source: In the tileSource property of your route, specify the URL of your MapTiler server.

Here is an example route configuration:

{
    "name": "My Custom Route",
    "routes": [
        {
            "routeKey": "myRoute",
            "bounds": {
                "coordinates": [0, 0],
                "width": 100,
                "height": 100
            },
            "tileSource": "https://{s}.tile.maptiler.io/tile/{z}/{x}/{y}.png?layer=custom&attribution={ attribution }"
        }
    ],
    "attribution": "Your map layer attribution here."
}

Conclusion

In this guide, we’ve explored the basics of customizing maps for an iPhone app using MapTiler and scripting techniques. By following these steps, you can now create your own seamless map tile layers that showcase your campus university map.

Keep in mind that this is just a starting point, and there are many more advanced topics to cover when working with mapping applications.

Last modified on 2023-05-18